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1. CELERY_LOADER myapp loaders You need to include the loader class name like this ERY_TASK_RESULT_ CELERY_LOADER myapp loaders Loader EXPIRES now defaults to 1 day Previous default setting was to expire in 5 days e AMQP backend Don t use different values for auto_delete This bug became visible with RabbitMQ 1 8 0 which no longer allows conflicting declarations for the auto_delete and durable settings If you ve already used celery with this backend chances are you have to delete the previous declara tion 11 34 2 0 0 213 Celery Documentation Release 2 5 5 camgqadm exchange delete celeryresults e Now uses pickle instead of cPickle on Python versions lt 2 5 cPickle is broken in Python lt 2 5 It unsafely and incorrectly uses relative instead of absolute imports so e g exceptions KeyError becomes celery exceptions KeyError Your best choice is to upgrade to Python 2 6 as while the pure pickle version has worse performance it is the only safe option for older Python versions 11 34 5 News e celeryev Curses Celery Monitor and Event Viewer This is a simple monitor allowing you to see what tasks are executing in real time and investigate tracebacks and results of ready tasks It also enables you to set new rate limits and revoke tasks Screenshot oo celeryev 1 1 1 UUID TASK WORKER TIME STATE 63aa2f2
2. e Added CELERY_REDIRECT_STDOUTS and CELERYD_REDIRECT_STDOUTS_LEVEL settings CELERY_REDIRECT_STDOUTS is used by celeryd and celerybeat All output to stdout and stderr will be redirected to the current logger if enabled CELERY_REDIRECT_STDOUTS_LEVEL decides the log level used and is WARNING by default e Added CELERYBEAT_SCHEDULER setting This setting is used to define the default for the S option to celerybeat Example CELERYBEAT_SCHEDULER djcelery schedulers DatabaseScheduler Added Task expires Used to set default expiry time for tasks e New remote control commands add_consumer and cancel_consumer add_consumer queue exchange exchange_type routing_key xoptions Tells the worker to declare and consume from the specified declaration cancel_consumer queue_name Tells the worker to stop consuming from queue by queue name Commands also added to celeryctl and inspect Example using celeryctl to start consuming from queue queue in exchange exchange of type direct using binding key key celeryctl inspect add_consumer queue exchange direct key celeryctl inspect cancel_consumer queue See celeryctl Management Utility for more information about the celeryctl program Another example using inspect gt gt gt from celery task control import inspect
3. can also specify options for named workers celeryd multi start image video data c 3 c image 10 celeryd n image myhost c 10 celeryd n video myhost c 3 celeryd n data myhost c 3 ranges and lists of workers in options is also allowed c 1 3 can also be written as c 1 2 3 celeryd multi start 5 c 3 c 1 3 10 celeryd multi n celerydl myhost c 10 celeryd multi n celeryd2 myhost c 10 celeryd multi n celeryd3 myhost c 10 celeryd multi n celeryd4 myhost c 3 celeryd multi n celeryd5 myhost c 3 lists also works with named workers celeryd multi start foo bar baz xuzzy c 3 c foo bar baz 10 celeryd multi n foo myhost c 10 celeryd multi n bar myhost c 10 celeryd multi n baz myhost c 10 celeryd multi n xuzzy myhost c 3 e The worker now calls the result backends process_cleanup method after task execution instead of before 11 34 2 0 0 219 Celery Documentation Release 2 5 5 e AMQP result backend now supports Pika 11 35 1 0 6 release date 2010 06 30 09 57 A M CEST RabbitMQ 1 8 0 has extended their exchange equivalence tests to include auto_delete and durable This broke the AMQP backend If you ve already used the AMQP backend this means you have to delete the previous definitions camqadm exchange delete celeryresults or python manage py camgqadm exchange delete celeryresults 11 36 1 0 5 release date 2010 06 01 02 36 P M CEST 11 36 1 Critical
4. celerybeat You can also start celerybeat with celeryd by using the B option this is convenient if you only intend to use one worker node celeryd B Celerybeat needs to store the last run times of the tasks in a local database file named celerybeat schedule by default so it needs access to write in the current directory or alternatively you can specify a custom location for this file celerybeat s home celery var run celerybeat schedul Note To daemonize celerybeat see Running celeryd as a daemon Using custom scheduler classes Custom scheduler classes can be specified on the command line the S argument The default scheduler is celery beat PersistentScheduler which is simply keeping track of the last run times in a local database file a shelve django celery also ships with a scheduler that stores the schedule in the Django database celerybeat S djcelery schedulers DatabaseScheduler Using django celery s scheduler you can add modify and remove periodic tasks from the Django Admin 2 6 Sets of tasks Subtasks and Callbacks e Subtasks Callbacks e Task Sets Results e Chords Important Notes 2 6 1 Subtasks New in version 2 0 The subtask type is used to wrap the arguments and execution options for a single task invocation subtask task_name_or_cls args kwargs options For convenience every task also has a shortcut to create subtasks task subtask
5. feed_tasks binding_key feed ERY_DEFAULT_EXCHANGE tasks ERY_DEFAULT_EXCHANGE_TYPE topic ERY_DEFAULT_ROUTING_KEY task default 4 CY 2 IG HHH CELERY_QUEUES is a map of queue names and their exchange type binding key if you don t et exchange or exchange type they will be taken from the CELERY_DEFAULT_EXCHANGE and CELERY_DEFAULT_EXCHANGE_TYPE settings Dn To route a task to the feed_tasks queue you can add an entry in the CELERY_ROUTES setting CELERY_ROUTES feeds tasks import_feed queue feed_tasks routing_key feed import hy You can also override this using the routing_key argument to Task apply_async orsend_task gt gt gt from feeds tasks import import_feed gt gt gt import_feed apply_async args http cnn com rss queue feed_tasks routing_key feed import To make server z consume from the feed queue exclusively you can start it with the Q option z celeryd Q feed_tasks hostname z example com Servers x and y must be configured to consume from the default queue 60 Chapter 2 User Guide Celery Documeniation Release 2 5 5 x celeryd Q default hostname x example com y celeryd Q default hostname y example com If you want you can even have your feed processing worker handle regular tasks as well maybe
6. workerl ok c j action re established worker2 ok connection re established TIP You can choose the worker s to receive the command by using the destination argument 11 38 1 0 3 223 Celery Documeniation Release 2 5 5 gt gt gt broadcast reset_broker_connection destination workerl workerl ok connection re established e New remote control command dump_reserved Dumps tasks reserved by the worker waiting to be executed gt gt gt from celery task control import broadcast gt gt gt broadcast dump_reserved reply True myworkerl lt TaskRequest gt e New remote control command dump_schedule Dumps the workers currently registered ETA schedule These are tasks with an eta or countdown argument waiting to be executed by the worker gt gt gt from celery task control import broadcast gt gt gt broadcast dump_schedule reply True wl w3 w2 70 2010 05 12 11 06 00 priO name opalfeeds Sks id 95b45760 4e args lt Feeds frec st kwargs page w4 0 2010 05 12 11 00 00 uskRequest We e sh_feed_slice name opalfes id 8d30a464edfe args kwargs pag g E 1 2010 05 12 11 12 00 kRequest name opalfeeds esh_fe a i id ab8bc59e 6cf8 44b8 O f1af57789758 args lt Feeds fre O
7. CELERY_DEFAULT_QUEUE default CELERY_DEFAULT_EXCHANGE default CELERY_DEFAULT_EXCHANGE_TYPE direct CELERY_DEFAULT_ROUTING_KEY default Here the CELERY_DEFAULT_QUEUE will be used to route tasks that doesn t have an explicit route The default exchange exchange type and routing key will be used as the default routing values for tasks and as the default values for entries in CELERY_QUEUES Specifying task destination The destination for a task is decided by the following in order 1 The Routers defined in CELERY_ROUTES 2 The routing arguments to Task apply_async 3 Routing related attributes defined on the Task itself It is considered best practice to not hard code these settings but rather leave that as configuration options by using Routers This is the most flexible approach but sensible defaults can still be set as task attributes Routers A router is a class that decides the routing options for a task All you need to define a new router is to create a class with a route_for_task method class MyRouter o t def route_for_task task args N kKwargs None if task myapp tasks compress_video return exchange video exchange_type topic routing_key video compress return If you return the queue key it will expand with the defined settings of that queue in CELERY_QUEUES
8. 2 2 Tasks 19 Celery Documentation Release 2 5 5 Basics Context Example Usage Logging Retrying a task if something fails Using a custom retry delay Task options General Message and routing options Task names Automatic naming and relative imports Decorating tasks Task States Result Backends x AMQP Result Backend Database Result Backend Built in States PENDING STARTED SUCCESS FAILURE RETRY x REVOKED Custom states Creating pickleable exceptions Creating custom task classes Instantiation Abstract classes Handlers On_retry How it works Tips and Best Practices Ignore results you don t want Disable rate limits if they re not used Avoid launching synchronous subtasks Performance and Strategies Granularity Data locality State Database transactions Example blog models py blog views py blog tasks py This guide gives an overview of how tasks are defined For a complete listing of task attributes and methods please see the API reference 2 2 1 Basics A task is a class that encapsulates a function and its execution options Given a function create_user that takes two arguments username and password you can create a task like this 20 Chapter 2 User Guide Celery Documeniation Release 2 5 5 from django contrib auth import User from celery task import task task def create_use
9. CELERY_TASK_RESULT_EXPIRES e Eventlet Fixed problem with shutdown Issue 457 e Broker transports can be now be specified using URLs The broker can now be specified as an URL instead This URL must have the format 11 10 2 4 1 175 Celery Documentation Release 2 5 5 transport user password hostname port virtual_host for example the default broker is written as amgqp guest guest localhost 5672 The scheme is required so that the host is identified as an URL and not just a host name User password port and virtual_host are optional and defaults to the particular transports default value Note Note that the path component virtual_host always starts with a forward slash This is necessary to distinguish between the virtual host empty and which are both acceptable virtual host names A virtual host of becomes amap guest guest localhost 5672 and a virtual host of empty becomes amqp guest guest localhost 5672 So the leading slash in the path component is always required In addition the BROKER_URL setting has been added as an alias to BROKER_HOST Any broker setting specified in both the URL and in the configuration will be ignored if a setting is not provided in the URL then the value from the configuration will be used as default Also programs now support the b broker option to specify a broker URL on the comma
10. Fixes e 2 3 0 Important Notes News Fixes 2 2 8 Security Fixes 2 2 7 e 2 2 6 Important Notes Fixes 2 2 5 Important Notes News Fixes e 2 2 4 Fixes 2 2 3 Fixes 22 2 Fixes 2 2 1 Fixes e 2 2 0 Important Notes News Fixes Experimental e 2 1 4 Fixes Documentation 2 1 3 2 1 2 Fixes 170 Chapter 11 Change history Celery Documeniation Release 2 5 5 11 1 2 5 5 release date 2012 06 06 16 00 P M BST by Ask Solem This is a dummy release performed for the following goals e Protect against force upgrading to Kombu 2 2 0 e Version parity with django celery 11 2 2 5 3 release date 2012 04 16 07 00 P M BST by Ask Solem e A bug causes messages to be sent with UTC timestamps even though CELERY_ENABLE_UTC was not enabled Issue 636 e celerybeat No longer crashes if an entry s args is set to None Issue 657 e Autoreload did not work if a module s __ file____ attribute was set to the modules pyc file Issue 647 e Fixes early 2 5 compatibility where __package__ does not exist Issue 638 11 3 2 5 2 release date 2012 04 13 04 30 P M BST by Ask Solem 11 3 1 News e Now depends on Kombu 2 1 5 e Django documentation has been moved to the main Celery docs See Django e New celeryd_init signal can be used to configure workers by hostname e Signal connect c
11. oy set_permissions gt set_permissions Tasks User Guide Added section on database transactions See issue 169 Routing User Guide Fixed typo feed gt queue feeds See issue 169 H 1ERYD_CONCURRENCY and Documented the default values for the CE CELERYD_PREFETCH MULTIPLIER settings Tasks User Guide Fixed typos in the subtask example celery signals Documented worker_process_init Daemonization cookbook Need to export DJANGO_SETTINGS_MODULE in etc default celeryd Added some more FAQs from stack overflow Daemonization cookbook Fixed typo CELERYD_LOGFILE CELERYD_PIDFILE to CELERYD_LOG_FILE CELERYD_PID_FILE Also added troubleshooting section for the init scripts 11 31 2 0 3 207 Celery Documentation Release 2 5 5 11 32 2 0 2 release date 2010 07 22 11 31 A M CEST e Routes When using the dict route syntax the exchange for a task could disappear making the task unroutable See issue 158 e Test suite now passing on Python 2 4 e No longer have to type PYTHONPATH to use celeryconfig in the current directory This is accomplished by the default loader ensuring that the current directory is in sys path when loading the config module sys path is reset to its original state after loading Adding the current working directory to sys path without the user knowing may be a security issue as this means someone c
12. 2 8 Routing Tasks 65 Celery Documentation Release 2 5 5 queue video routing_key video compress becomes gt queue video exchange video exchange_type topic routing_key video compress You install router classes by adding them to the CELERY_ROUTES setting CELERY_ROUTES MyRouter Router classes can also be added by name CELERY_ROUTES myapp routers MyRouter For simple task name gt route mappings like the router example above you can simply drop a dict into CELERY_ROUTES to get the same behavior CELERY_ROUTES myapp tasks compress_video queue video routing_key video compress tt The routers will then be traversed in order it will stop at the first router returning a true value and use that as the final route for the task 2 9 Monitoring and Management Guide e Introduction e Workers celeryctl Management Utility Commands Specifying destination nodes Django Admin Monitor Starting the monitor Shutter frequency x Using outside of Django celeryev Curses Monitor celerymon Web monitor RabbitMQ Inspecting queues e Redis Inspecting queues e Munin e Events Snapshots Custom Camera Event Reference x Task Events Worker Events 66 Chapter 2 User Guide Celery Documeniation Release 2 5 5 2 9 1 Introdu
13. When tasks are sent we don t send any actual function code just the name of the task to execute When the worker then receives the message it can look up the name in its task registry to find the execution code This means that your workers should always be updated with the same software as the client This is a drawback but the alternative is a technical challenge that has yet to be solved 2 2 11 Tips and Best Practices Ignore results you don t want If you don t care about the results of a task be sure to set the ignore_result option as storing results wastes time and resources task ignore_result True def mytask something Results can even be disabled globally using the CELERY_IGNORE_RESULT setting Disable rate limits if they re not used Disabling rate limits altogether is recommended if you don t have any tasks using them This is because the rate limit subsystem introduces quite a lot of complexity Set the CELERY_DISABLE_RATE_LIMITS setting to globally disable rate limits CELERY_DISABLE_RATE LIMITS Avoid launching synchronous subtasks Having a task wait for the result of another task is really inefficient and may even cause a deadlock if the worker pool is exhausted Make your design asynchronous instead for example by using callbacks Bad 32 Chapter 2 User Guide Celery Documeniation Release 2 5 5 task
14. arguments None durable lt type bool gt auto_delete lt type boo auto_delete False can_cache_declaration declare nowait False Declare the exchange Creates the exchange on the broker Parameters nowait If set the server will not respond and a response will not be waited for Default is False delete if_unused False nowait False Delete the exchange declaration on server Parameters e if unused Delete only if the exchange has no bindings Default is False e nowait If set the server will not respond and a response will not be waited for Default is False delivery_mode 2 durable True name publish message routing_key None mandatory False immediate False exchange None Publish message Parameters e message Message instance to publish e routing_key Routing key e mandatory Currently not supported e immediate Currently not supported type direct class AMOPBackend Producer channel exchange None routing_key None serializer None auto_declare None compression None on_return None Message Producer Parameters e channel Connection or channel e exchange Optional default exchange e routing_key Optional default routing key e serializer Default serializer Default is json e compression Default compression method Default is no compression 13 6 Internal Module Reference 359 Celery
15. celery worker buckets chain_from_iterable chain from_iterable iterable gt chain object Alternate chain contructor taking a single iterable argument that evaluates lazily 13 6 7 celery worker heartbeat e celery worker heartbeat j 336 Chapter 13 Internals Celery Documeniation Release 2 5 5 celery worker heartbeat This is the internal thread that sends heartbeat events at regular intervals copyright 3 2009 2012 by Ask Solem license BSD see LICENSE for more details class celery worker heartbeat Heart timer eventer interval None Timer sending heartbeats at regular intervals Parameters timer Timer instance e eventer Event dispatcher used to send the event e interval Time in seconds between heartbeats Default is 30 seconds start stop 13 6 8 celery worker state e celery worker state j celery worker state Internal worker state global This includes the currently active and reserved tasks statistics and revoked tasks copyright 3 2009 2012 by Ask Solem license BSD see LICENSE for more details class celery worker state Persistent filename close db merge d open save storage lt module shelve from usr lib python2 7 shelve pyc gt sync d celery worker state REVOKES_ MAX 10000 maximum number of revokes to keep in memory celery worker state REVOKE_EXPIRES 3600 how many seconds a revoke will b
16. class celery backends base BaseDictBackend args kwargs delete _taskset taskset_id forget task_id get_result task_id Get the result of a task get_status task_id Get the status of a task get_task_meta task_id cache True get_taskset_meta taskset_id cache True get_traceback task_id Get the traceback for a failed task reload_task_result task_id reload_taskset_result taskset_id 13 6 Internal Module Reference 353 Celery Documentation Release 2 5 5 restore _taskset taskset_id cache True Get the result for a taskset save_taskset taskset_id result Store the result of an executed taskset store_result task_id result status traceback None kwargs Store task result and status class celery backends base DisabledBackend args kwargs get_result args kwargs get_status args kwargs get_traceback args kwargs store_result args kwargs wait_for args kwargs class celery backends base KeyValueStoreBackend args kwargs chord_keyprefix chord unlock delete key get key get_key_for_chord taskset_id Get the cache key for the chord waiting on taskset with given id get_key_for_task fask_id Get the cache key for a task by id get_key_for_taskset faskset_id Get the cache key for a taskset by id get_many fask_ids timeout None interval 0 5 mget keys set key value task_keyprefix
17. date_done id result status task_id to_dict traceback class celery db models TaskSet taskset_id result TaskSet result 13 6 Internal Module Reference 375 Celery Documentation Release 2 5 5 date_done id result taskset_id to_dict 13 6 43 celery db session celery db session ResultSession dburi kwargs celery db session create_session dburi short_lived_sessions False kwargs celery db session get_engine dburi kwargs celery db session setup_results engine 13 6 44 celery utils e celery utils j celery utils Utility functions copyright 3 2009 2012 by Ask Solem license BSD see LICENSE for more details exception celery utils NotAPackage celery utils abbr S max ellipsis celery utils abbrtask S max celery utils chunks it n Split an iterator into chunks with n elements each Examples n 2 gt gt gt x chunks iter 0 1 2 3 4 5 6 7 8 9 10 2 gt gt gt list x 0 1 2 3 4 5 6 7 8 9 10 n 3 gt gt gt x chunks iter 0 1 2 3 4 5 6 7 8 9 10 3 gt gt gt list x 0 1 2 3 4 5 6 7 8 9 10 celery utils cry Return stacktrace of all active threads From https gist github com 737056 celery utils cwd_in_path args kwds celery utils deprecated description None deprecation None removal None alternative None 376 Chapter 13 Internals
18. foo reload True If you don t specify any modules then all known tasks modules will be imported reloaded 2 4 Workers Guide 47 Celery Documeniation Release 2 5 5 gt gt gt broadcast pool_restart arguments reload True The modules argument is a list of modules to modify reload specifies whether to reload modules if they have previously been imported By default reload is disabled The pool_restart command uses the Python reload function to reload modules or you can provide your own custom reloader by passing the re loader argument Note Module reloading comes with caveats that are documented in reload Please read this documentation and make sure your modules are suitable for reloading See also e http pyunit sourceforge net notes reloading html e http www indelible org ink python reloading e http docs python org library functions html reload Writing your own remote control commands Remote control commands are registered in the control panel and they take a single argument the current ControlDispatch instance From there you have access to the active Consumer if needed Here s an example control command that restarts the broker connection from celery worker control import Panel Panel register def reset_connection panel panel logger critical Connection reset by remote control panel consumer reset_connection return ok connection reset These c
19. lserver configuration EMAIL HOST EMAIL_PORT mail vandelay com 25 Wows 3 2 18 Events CELERY_SEND EVENTS Send events so the worker can be monitored by tools like celerymon CELERY_SEND_TASK_SENT_EVENT New in version 2 2 If enabled a task sent event will be sent for every task so tasks can be tracked before they are consumed by a worker Disabled by default CELERY_EVENT_SERIALIZER Message serialization format used when sending event messages Default is json See Serializers 102 Chapter 3 Configuration and defaults Celery Documeniation Release 2 5 5 3 2 19 Broadcast Commands CELERY_BROADCAST_QUEUE Name prefix for the queue used when listening for broadcast messages The workers host name will be appended to the prefix to create the final queue name Default is celeryctl CELERY_BROADCAST_EXCHANGE Name of the exchange used for broadcast messages Default is celeryctl CELERY_BROADCAST_EXCHANGE_TYPE Exchange type used for broadcast messages Default is fanout 3 2 20 Logging CELERYD_HIJACK_ROOT_LOGGER New in version 2 2 By default any previously configured logging options will be reset because the Celery programs hijacks the root logger If you want to customize your own logging then you can disable this behavior Note Logging can also be customized by connecting to the celery signals setup_logging signal CELERYD_LOG_COLOR
20. rate_limit 10 s 3 2 Configuration Directives 3 2 1 Time and date settings CELERY_ENABLE_UTC If enabled dates and times in messages will be converted to use the UTC timezone Note that workers running Celery versions below 2 5 will assume a local timezone for all messages so only enable if all workers have been upgraded Disabled by default UTC will be enabled by default in version 3 0 3 2 2 CELERY_TIMEZONE Configure Celery to use a custom time zone The timezone value can be any time zone supported by the pyt z library pytz must be installed for the selected zone to be used If not set then the systems default local time zone is used 3 2 3 Task settings CELERY_ANNOTATIONS This setting can be used to rewrite any task attribute from the configuration The setting can be a dict or a list of annotation objects that filter for tasks and return a map of attributes to change This will change the rate_limit attribute for the tasks add task CELERY_ANNOTATIONS tasks add rate_limit 10 s or change the same for all tasks 88 Chapter 3 Configuration and defaults Celery Documeniation Release 2 5 5 CELERY_ANNOTATIONS rate_limit 10 s You can change methods too for example the on_failure handler def my_on_failure self exc task_id args kwargs einfo print Oh no Task failed r exc CELERY_ANNOTATIONS on_failure my_on
21. 0 8 17 2 at midnight and every two hours during office hours day_of week eA list of integers from 0 6 where Sunday 0 and Saturday 6 that represent the days of a week that execution should occur eA string representing a crontab pattern This may get pretty advanced like day_of_week mon fri for weekdays only Beware that day_of_week 2 does not literally mean every two days but every day that is divisible by two 278 Chapter 12 API Reference Celery Documeniation Release 2 5 5 is due last_run_at Returns tuple of two items is_due next_time_to_run where next time to run is in seconds See celery schedules schedule is_due for more information remaining_estimate last_run_at Returns when the periodic task should run next as a timedelta class celery schedules crontab_parser max_ 60 Parser for crontab expressions Any expression of the form groups see BNF grammar below is accepted and expanded to a set of numbers These numbers represent the units of time that the crontab needs to run on digit ger TOE ee Oe dow gee Ta 4 oes number digit dow steps number range number number numspec x range expr numspec steps groups expr expr The parser is a general purpose one useful for parsing hours minutes and day_of_week expressions Example usage gt gt gt minutes crontab_parser
22. 1 release_lock lambda cache delete lock_id 113 Celery Documentation Release 2 5 5 logger debug Importing feed Ss feed_url if acquire_lock try feed Feed objects import_feed feed_url finally release_lock return feed url logger debug Feed SS is already being imported by another worker feed_url return 5 2 Running celeryd as a daemon Celery does not daemonize itself please use one of the following daemonization tools e Generic init scripts Init script celeryd x Example configuration x Example Django configuration x Example Django configuration Using Virtualenv x Available options Init script celerybeat x Example configuration x Example Django configuration x Available options Troubleshooting e supervisord e launchd OS X e Windows 5 2 1 Generic init scripts See the contrib generic init d directory Celery distribution This directory contains generic bash init scripts for celeryd that should run on Linux FreeBSD OpenBSD and other Unix platforms Init script celeryd Usage etc init d celeryd start stop restart status Configuration file etc default celeryd To configure celeryd you probably need to at least tell it where to change directory to when it starts to find your celeryconfig 114 Chapter 5 Cookbook Celery Documeniation Release 2 5 5 Example configuration This is an example configuration for a Python proj
23. 6 2 1 Issue Trackers Bugs for a package in the Celery ecosystem should be reported to the relevant issue tracker e Celery http github com celery celery issues e Dyjango Celery http github com celery django celery issues e Celery Pylons http bitbucket org ianschenck celery pylons issues e Kombu http github com celery kombu issues If you are unsure of the origin of the bug you can ask the Mailing list or just use the Celery issue tracker 122 Chapter 6 Contributing Celery Documeniation Release 2 5 5 6 3 Versions Version numbers consists of a major version minor version and a release number Since version 2 1 0 we use the versioning semantics described by semver http semver org Stable releases are published at PyPI while development releases are only available in the GitHub git repository as tags All version tags starts with v so version 0 8 0 is the tag v0 8 0 6 4 Branches Current active version branches e master http github com celery celery tree master e 3 0 devel http github com celery celery tree 3 0 devel You can see the state of any branch by looking at the Changelog https github com celery celery blob master Changelog If the branch is in active development the topmost version info should contain metadata like release date TBA status DEVELOPMENT branch master The status field can be one of e PLANNING The branch is currently experimental and in th
24. CELERY_DEFAULT_QUEUE default CELERY_DEFAULT_EXCHANGE_TYPE direct CELERY_DEFAULT_ROUTING_KEY default Note In Celery the routing_key is the key used to send the message while binding_key is the key the queue is bound with In the AMQP API they are both referred to as the routing key Exchange types The exchange type defines how the messages are routed through the exchange The exchange types defined in the stan dard are direct topic fanout and headers Also non standard exchange types are available as plug ins to RabbitMQ like the last value cache plug in by Michael Bridgen Direct exchanges Direct exchanges match by exact routing keys so a queue bound by the routing key video only receives messages with that routing key 62 Chapter 2 User Guide Celery Documeniation Release 2 5 5 Topic exchanges Topic exchanges matches routing keys using dot separated words and the wildcard characters matches a single word and matches zero or more words With routing keys like usa news usa weather norway news and norway weather bindings could be x news all news usa all items in the USA or usa weather all USA weather items Related API commands exchange declare exchange_name type passive durable auto_delete internal Declares an exchange by name Parameters e passive Passive means the exchange won t be created but you can use this to check if the ex
25. New in version 2 3 A chord is a task that only executes after all of the tasks in a taskset has finished executing Let s calculate the sum of the expression 1 1 2 2 3 3 n n up to a hundred digits First we need two tasks add and tsum sum is already a standard function from celery task import task task def add x y return x y 2 6 Sets of tasks Subtasks and Callbacks 55 Celery Documentation Release 2 5 5 task def tsum numbers return numbers Now we can use a chord to calculate each addition step in parallel and then get the sum of the resulting numbers gt gt gt from celery task import chord gt gt gt from tasks import add tsum gt gt gt chord add subtask i i for i in 100 tsum subtask get This is obviously a very contrived example the overhead of messaging and synchronization makes this a lot slower than its Python counterpart i i for i in 100 The synchronization step is costly so you should avoid using chords as much as possible Still the chord is a powerful primitive to have in your toolbox as synchronization is a required step for many parallel algorithms Let s break the chord expression down gt gt gt callback tsum subtask gt gt gt header add subtask i i for i in 100 gt gt gt result chord header callback gt gt gt result get 9900 Remember the callback can only be executed after a
26. Reads and returns the current pid 13 6 Internal Module Reference 389 Celery Documentation Release 2 5 5 release args Release lock remove Removes the lock remove_if stale Removes the lock if the process is not running does not respond to signals write _pid class celery platforms Signals Convenience interface to signals If the requested signal is not supported on the current platform the operation will be ignored Examples gt gt gt from celery platforms import signals gt gt gt signals INT my_handler gt gt gt signals INT handler gt gt gt signals supported INT True gt gt gt signals signum INT gt gt gt signals ignore USRI1 gt gt gt signals USRi signals ignored True gt gt gt signals reset USR1 gt gt gt signals USR1 signals default True gt gt gt signals update INT exit_handler ERM exit_handler UP hup_handler a T default 0 ignore signal_names Ignore signal using SIG_IGN Does nothing if the platform doesn t support signals or the specified signal in particular ignored 1 reset signal_names Reset signals to the default signal handler Does nothing if the platform doesn t support signals or the specified signal in particular signum signal_name Get signal number from signal name supported signal_name Returns true value if signal_name exists on this pla
27. body class Pool TimeoutHandler processes cache t_soft t_hard body Pool apply func args kwds Equivalent of apply builtin Pool apply_asyne func args kwds callback None accept_callback None timeout_callback None waitforslot False error_callback None soft_timeout None timeout None Asynchronous equivalent of apply builtin Callback is called when the functions return value is ready The accept callback is called when the job is accepted to be executed Simplified the flow is like this 13 6 Internal Module Reference 343 Celery Do cumentation Release 2 5 5 gt gt gt if accept_callback ae accept_callback gt gt gt retval func args kwds gt gt gt if callback callback retval Pool close Pool grow n Pool imap func iterable chunksize 1 lost_worker_timeout 10 0 Equivalent of itertools imap can be MUCH slower than Pool map Pool imap_unordered func iterable chunksize 1 lost_worker_timeout 10 0 Like imap method but ordering of results is arbitrary Pool Join Pool map func iterable chunksize None Equivalent of map builtin Pool map_asynce func iterable chunksize None callback None Asynchronous equivalent of map builtin Pool restart Pool shrink n Pool terminate class celery concurrency processes pool PoolThread args kwargs close run terminate class celery concurrency proces
28. classmethod AsyncResult task_id Get AsyncResult instance for this kind of task Parameters task_id Task id to get result for class ErrorMail task kwargs Defines how and when task error e mails should be sent Parameters task The task instance that raised the error subject and body are format strings which are passed a context containing the following keys name Name of the task UUID of the task eXC String representation of the exception eargs Positional arguments ekwargs Keyword arguments traceback String representation of the traceback ehostname Worker hostname should_send context exc Returns true or false depending on if a task error mail should be sent for this type of error exception BaseTask MaxRetriesExceededError The tasks max restart limit has been exceeded BaseTask after_return status retval task_id args kwargs einfo Handler called after the task returns Parameters e status Current task state e retval Task return value exception e task_id Unique id of the task e args Original arguments for the task that failed e kwargs Original keyword arguments for the task that failed e einfo ExceptionInfo instance containing the traceback if any The return value of this handler is ignored classmethod BaseTask apply args None kwargs None options Execute this task locally by blocking until the task returns Parameters 260
29. gt gt gt inspect add_consumer queue queue exchange exchange xchange_type direct routing_key key durable F auto_delete T gt gt gt inspect cancel_consumer queue e celerybeat Now logs the traceback if a message can t be sent e celerybeat Now enables a default socket timeout of 30 seconds e READMF introduction homepage Added link to Flask Celery 11 30 2 1 0 release date 2010 10 08 12 00 P M CEST 11 30 2 1 0 199 Celery Documeniation Release 2 5 5 11 30 1 Important Notes e Celery is now following the versioning semantics defined by semver This means we are no longer allowed to use odd even versioning semantics By our previous version ing scheme this stable release should have been version 2 2 e Now depends on Carrot 0 10 7 e No longer depends on SQLAIchemy this needs to be installed separately if the database result backend is used e django celery now comes with a monitor for the Django Admin interface This can also be used if you re not a Django user See Django Admin Monitor and Using outside of Django for more information e If you get an error after upgrading saying AttributeError module object has no attribute system Then this is because the celery platform module has been renamed to celery platforms to not collide with the built in plat form module You have to remove the old plat form py and maybe platform pyc file from your previous Celery in
30. task base Batches flush_every 100 flush_interval 10 def count_click requests 12 25 celery contrib batches 289 Celery Documentation Release 2 5 5 from collections import Counter count Counter request kwargs url for request in requests for url count in count items print gt gt gt Clicks s gt 6s url count Registering the click is done as follows gt gt gt count_click delay url http example com Warning For this to work you have to set CELERYD_PREFETCH_MULTIPLIER to zero or some value where the final multiplied value is higher than flush_every In the future we hope to add the ability to direct batching tasks to a channel with different QoS requirements than the task channel copyright 3 2009 2012 by Ask Solem license BSD see LICENSE for more details API class celery contrib batches Batches apply_ buffer requests args kwargs debug msg execute request pool loglevel logfile flush requests flush_every 10 Maximum number of message in buffer flush_interval 30 Timeout in seconds before buffer is flushed anyway logger run requests class celery contrib batches SimpleRequest id name args kwargs delivery_info hostname Pickleable request args positional arguments delivery_info None message delivery information classmethod from_request request hostname None worker node name id
31. 258 Chapter 12 API Reference Celery Documeniation Release 2 5 5 celery task periodic_task args options Decorator to create a task class out of any callable Examples task def refresh_feed url return Feed objects get url url refresh With setting extra options and using retry from celery task import current task exchange feeds def refresh_feed url try return Feed objects get url url refresh except socket error exc current retry exc exc Calling the resulting task gt gt gt refresh_feed http example com rss eed http example com rss gt gt gt gt refresh_feed delay http example com rss lt AsyncResult 8998d0f4 da0b 4669 ba03 d5ab5ac6ad5d class celery task Task Task base class When called tasks apply the run method This method must be defined by all tasks that is unless the ___call___ method is overridden See also celery task base BaseTask 12 6 celery task base e celery task base j 12 6 1 celery task base The task implementation has been moved to celery app task copyright 3 2009 2012 by Ask Solem license BSD see LICENSE for more details class celery task base BaseTask Task base class When called tasks apply the run method This method must be defined by all tasks that is unless the call_ _ method is overridden 12 6 celery task base 259 Celery Documentation Release 2 5 5
32. Database tables will be created the first time the monitor is run By default an sqlite3 database file named djcelerymon db is used so make sure this file is writeable by the user running the monitor If you want to store the events in a different database e g MySQL then you can configure the DATABASE settings directly in your Celery config module See http docs djangoproject com en dev ref settings databases for more in formation about the database options available You will also be asked to create a superuser and you need to create one to be able to log into the admin later Creating table auth_permission Creating table auth_group_permissions ares You just installed Django s auth system which means you don t have any superusers defined Would you like to create one now yes no yes Username Leave blank to use username username Email address me example com Password x x x x x Password again x Superuser created successfully besa Django version 1 2 1 using settings celeryconfig 70 Chapter 2 User Guide Celery Documeniation Release 2 5 5 Development server is running at http 127 0 0 1 8000 Quit the server with CONTROL C Now that the service is started you can visit the monitor at http 127 0 0 1 8000 and log in using the user you created For a list of the command line options supported by djcelerymon please see djcelerymon help celeryev C
33. It is Available as task request hostname now easier for app subclasses to extend how they are pickled see celery app AppPickler 11 12 2 3 4 179 Celery Documentation Release 2 5 5 11 14 2 Fixes e purge discard_all was not working correctly Issue 455 e The coloring of log messages didn t handle non ASCII data well Issue 427 e Windows the multiprocessing pool tried to import os kill even though this is not available there Issue 450 e Fixes case where the worker could become unresponsive because of tasks exceeding the hard time limit e The task sent event was missing from the event reference e ResultSet iterate now returns results as they finish Issue 459 This was not the case previously even though the documentation states this was the expected behav ior e Retries will no longer be performed when tasks are called directly using ___call__ Instead the exception passed to ret ry will be re raised e Eventlet no longer crashes if autoscale is enabled growing and shrinking eventlet pools is still not supported e py24 target removed from tox ini 11 15 2 3 1 release date 2011 08 07 08 00 P M BST 11 15 1 Fixes e The CEL ERY_AMOP_TASK_RESULT_1 EXPIRES setting did not work resulting in an AMQP related error about not being able to serialize floats while trying to publish task states Issue 446 11 16 2 3 0 release date 2011
34. None task id kwargs keyword arguments name None task name 290 Chapter 12 API Reference Celery Documeniation Release 2 5 5 12 26 celery contrib migrate e celery contrib migrate j 12 26 1 celery contrib migrate Migration tools copyright 3 2009 2012 by Ask Solem license BSD see LICENSE for more details class celery contrib migrate State count 0 strtotal total_apx 0 celery contrib migrate migrate_task producer body_ message re move_props application_headers content_type content_encoding celery contrib migrate migrate_tasks source dest timeout 1 0 app None migrate None callback None 12 27 celery contrib rdb Remote debugger for Celery tasks running in multiprocessing pool workers Inspired by http snippets dzone com posts show 7248 Usage from celery contrib import rdb from celery task import task task def add x y result x y rdb set_trace return result Environment Variables CELERY_RDB_HOST Hostname to bind to Default is 127 0 01 which means the socket will only be accessible from the local host CELERY_RDB_PORT Base port to bind to Default is 6899 The debugger will try to find an available port starting from the base port The selected port will be logged by celeryd copyright 3 2009 2012 by Ask Solem 12 26 celery contrib migrate 291 Celery Documentation Release 2 5 5 license BSD see LIC
35. Ping Enable disable events Adding Reloading modules x Example Writing your own remote control commands e Inspecting workers Dump of registered tasks Dump of currently executing tasks Dump of scheduled ETA tasks Dump of reserved tasks 2 4 1 Starting the worker You can start celeryd to run in the foreground by executing the command celeryd loglevel INFO You probably want to use a daemonization tool to start celeryd in the background See Running celeryd as a daemon for help using celeryd with popular daemonization tools For a full list of available command line options see ce leryd or simply do celeryd help You can also start multiple workers on the same machine If you do so be sure to give a unique name to each individual worker by specifying a host name with the hostname n argument celeryd loglevel INFO concurrency 10 n workerl example com celeryd loglevel INFO concurrency 10 n worker2 example com celeryd loglevel INFO concurrency 10 n worker3 example com 2 4 2 Stopping the worker Shutdown should be accomplished using the TERM signal When shutdown is initiated the worker will finish all currently executing tasks before it actually terminates so if these tasks are important you should wait for it to finish before doing anything drastic like sending the KILL signal 42 Chapter 2 User Guide Celery Documeniation Release 2 5 5 I
36. Task Add attribute ignore_result Don t store the status and return value This means you can t use the cel ery result AsyncResult to check if the task is done or get its return value Only use if you need the performance and is able live without these features Any exceptions raised will store the return value status as usual Task Add attribute disable_error_emails to disable sending error emails for that task 11 48 0 4 1 237 Celery Documentation Release 2 5 5 Should now work on Windows although running in the background won t work so using the detach argument results in an exception being raised Added support for statistics for profiling and monitoring To start sending statistics start celeryd with the Statistics option Then after a while you can dump the results by running python manage py celerystats See celery monitoring for more information The celery daemon can now be supervised i e it is automatically restarted if it crashes To use this start celeryd with the supervised option or alternatively S views apply View applying a task Example http e com celery apply task_name argl arg2 kwargl a amp kwarg2 b Warning Use with caution Do not expose this URL to the public without first ensuring that your code is safe Refactored celery task It s now split into three modules celery task Contains apply_async delay_task discard_all and task shortcuts plus imp
37. TaskSetResult taskset_id results kwargs Create celery result TaskSetResult instance worker_main argv None Run celeryd using argv Uses sys argv if argv is not specified Worker kwargs Create new Worker instance Beat kwargs Create new Beat instance broker_connection hostname None userid None password None _ virtual_host None port None ssl None insist None connect_timeout None transport None transport_options None kwargs Establish a connection to the message broker Parameters e hostname defaults to the BROKER_HOST setting e userid defaults to the BROKER_USER setting e password defaults to the BROKER_PASSWORD setting e virtual_host defaults to the BROKER_VHOST setting e port defaults to the BROKER_PORT setting e ssl defaults to the BROKER_USE_SSL setting e insist defaults to the BROKER_INSIST setting e connect_timeout defaults to the BROKER_CONNECTION_TIMEOUT setting e backend_cls defaults to the BROKER_TRANSPORT setting returns kombu connection BrokerConnection 12 1 celery app 247 Celery Documentation Release 2 5 5 with_default_connection fun With any function accepting connection and connect_timeout keyword arguments establishes a default connection if one is not already passed to it Any automatically established connection will be closed after the function
38. This test assumes that you put your example add task in maypp tasks so adjust the import for wherever you put the class 112 Chapter 4 Django CHAPTER 5 Cookbook 5 1 Creating Tasks e Ensuring a task is only executed one at a time j 5 1 1 Ensuring a task is only executed one at a time You can accomplish this by using a lock In this example we ll be using the cache framework to set a lock that is accessible for all workers It s part of an imaginary RSS feed importer called djangofeeds The task takes a feed URL as a single argument and imports that feed into a Django model called Feed We ensure that it s not possible for two or more workers to import the same feed at the same time by setting a cache key consisting of the MD5 checksum of the feed URL The cache key expires after some time in case something unexpected happens you never know right from celery task import Task from django core cache import cache from django utils hashcompat import md5_constructor as md5 from djangofeeds models import Feed LOCK_EXPIRE 60 5 Lock expire class FeedImporter Task name feed import def run feed_url x kwargs logger s get_logger kwargs feed_url_digest md5 feed_url hexdigest lock_id s lock s name feed_url_hexdigest f TG gt aaa at fe L Ll J r 2A Cz gt acquire_lock lambda cache add lock_id true LOCK_EXPIRE Vz
39. Warning This won t affect workers with the CELERY_DISABLE E_LIMITS setting on To re enable rate limits then you have to restart the worker Revoking tasks All worker nodes keeps a memory of revoked task ids either in memory or persistent on disk see Persistent revokes When a worker receives a revoke request it will skip executing the task but it won t terminate an already executing task unless the terminate option is set If terminate is set the worker child process processing the task will be terminated The default signal sent is TERM but you can specify this using the signal argument Signal can be the uppercase name of any signal defined in the signal module in the Python Standard Library Terminating a task also revokes it Example gt gt gt from celery task control import revoke gt gt gt revoke d9078da5 9915 40a0 bfal 392c7bde42ed gt gt gt revoke d9078da5 9915 40a0 bfal 392c7bde42ed terminate T gt gt gt revoke d9078da5 9915 40a0 bfal 392c7bde42ed terminate Signal SIGKILL 46 Chapter 2 User Guide Celery Documeniation Release 2 5 5 Remote shutdown This command will gracefully shut down the worker remotely gt gt gt broadcast Shutdown shutdown all workers gt gt gt broadcast Shutdown destination workerl example com Ping This command requests a ping from alive workers The workers reply with the string po
40. celeryd P eventlet c 1000 Examples See the Eventlet examples directory in the Celery distribution for some examples taking use of Eventlet support 2 13 Signals 80 Chapter 2 User Guide Celery Documeniation Release 2 5 5 e Basics e Signals Task Signals x task_sent task_prerun task_postrun task failure Worker Signals celeryd_init x worker_init worker_ready x worker_process_init x worker_shutdown Celerybeat Signals x beat_init beat_embedded_init Eventlet Signals eventlet_pool_started eventlet_pool_preshutdown eventlet_pool_postshutdown eventlet_pool_apply Logging Signals setup_logging after_setup_logger after_setup_task_logger Signals allows decoupled applications to receive notifications when certain actions occur elsewhere in the application Celery ships with many signals that you application can hook into to augment behavior of certain actions 2 13 1 Basics Several kinds of events trigger signals you can connect to these signals to perform actions as they trigger Example connecting to the task_sent signal from celery signals import task_sent task_sent connect def task_sent_handler sender task_id task args kwargs x xkwds print Got signal task_sent for task id s task_id Some signals also have a sender which you can filter by For example the task_sent signal uses the task name as a sender so you ca
41. def update_page_info url page fetch_page delay url get info parse_page delay url page get store_page_info delay url info task def fetch_page url return myhttplib get url task def parse_page url page return myparser parse_document page task def store_page_info url info return PageInfo objects create url info Good task ignore_result True def update_page_info url o parse age e page llback subtask parse_page callback subtask store_page_info fetch_page delay url ca task ignore_result True def fetch_page url callback yes page myhttplib get url if callback 2 S subtask callback delay url page task ignore_result T def parse_page url page callback N eS info myparser parse_document page if callback subtask callback delay url info task ignore_result T def store_page_info url info PageInfo objects create url info We use subtask here to safely pass around the callback task subtask is a subclass of dict used to wrap the arguments and execution options for a single task invocation See also Subtasks for more information about subtasks 2 2 12 Performance and Strategies Granularity The task granularity is the amount of computation needed by each subtask In general it is better to split the problem up into many small tasks than have a few long running tasks 2 2 Tasks 33 Celery Documentation R
42. e serializer Serializer to use Default is auto detect e compression Compression method to use Default is none e headers Mapping of arbitrary headers to pass along with the message body e exchange Override the exchange Note that this exchange must have been declared e declare Optional list of required entities that must have been de clared before publishing the message The entities will be declared using maybe_declare e retry Retry publishing or declaring entities if the connection is lost 360 Chapter 13 Internals Celery Documeniation Release 2 5 5 e retry_policy Retry configuration this is the keywords supported by ensure e properties Additional message properties see AMQP spec release revive channel Revive the producer after connection loss routing_key serializer None class AMOPBackend Queue name exchange None routing_key channel None kwargs A Queue declaration Parameters e name See name e exchange See exchange e routing_key See routing_key e channel See channel e durable See durable e exclusive See exclusive e auto_delete See auto_delete e queue_arguments See queue_arguments e binding_arguments See binding_arguments name Name of the queue Default is no name default queue destination exchange The Exchange the queue binds to routing_key The routing key if an
43. json This was not the case before the values in CELERY_QUEUES would take precedence e Worker crashed if the value of CELERY_TASK_ERROR_WHITELIST was not an iterable e apply Make sure kwargs task_id is always set 206 Chapter 11 Change history Celery Documeniation Release 2 5 5 e AsyncResult traceback Now returns None instead of raising KeyError if traceback is missing inspect Replies did not work correctly if no destination was specified Can now store result metadata for custom states celeryd A warning is now emitted if the sending of task error emails fails celeryev Curses monitor no longer crashes if the terminal window is resized See issue 160 celeryd On OS X it is not possible to run os exec in a process that is threaded This breaks the SIGHUP restart handler and is now disabled on OS X emitting a warning instead See issue 152 e celery execute trace Properly handle raise str which is still allowed in Python 2 4 See issue 175 Using urllib2 in a periodic task on OS X crashed because of the proxy auto detection used in OS X This is now fixed by using a workaround See issue 143 Debian init scripts Commands should not run in a sub shell See issue 163 Debian init scripts Use the absolute path of celeryd to allow stat See issue 162 11 31 2 Documentation e getting started broker installation Fixed typo
44. opts Ignored Example import atexit from celery platforms import detached create_pidlock with detached logfile var log app log pidfile var run app pid uid nobody pidlock create_pidlock var run app pid acquire atexit register pidlock release program run logfile var log app log celery platforms get_fdmax default None cel cel Returns the maximum number of open file descriptors on this system Parameters default Value returned if there s no file descriptor limit ery platforms initgroups uid gid ery platforms maybe_drop_privileges uid None gid None Change process privileges to new user group If UID and GID is specified the real user group is changed 13 6 Internal Module Reference 391 Celery Documentation Release 2 5 5 If only UID is specified the real user is changed and the group is changed to the users primary group If only GID is specified only the group is changed celery platforms parse_gid gid Parse group id gid can be an integer gid or a string group name if a group name the gid is taken from the password file celery platforms parse_uid uid Parse user id uid can be an integer uid or a string user name if a user name the uid is taken from the password file celery platforms pyimplementation celery platforms set_mp_process_title progname info None hostname None rate_limit False Set th
45. snapshots Fixed race condition leading to loss of events celeryd Reject tasks with an eta that cannot be converted to a time stamp See issue 209 concurrency processes pool The semaphore was released twice for each task both at ACK and result ready This has been fixed and it is now released only once per task docs configuration Fixed typo CELERYD_SOFT_TASK_TIME_LIMIT gt CELERYD_TASK_SOFT_TIME_LIMIT See issue 214 control command dump_scheduled was using old info attribute celeryd multi Fixed set changed size during iteration bug occurring in the restart command celeryd Accidentally tried to use additional command line arguments This would lead to an error like got multiple values for keyword argument concurrency Additional command line arguments are now ignored and does not produce this error How ever we do reserve the right to use positional arguments in the future so please do not depend on this behavior celerybeat Now respects routers and task execution options again celerybeat Now reuses the publisher instead of the connection Cache result backend Using float as the expires argument to cache set is deprecated by the memcached libraries so we now automatically cast to int unit tests No longer emits logging and warnings in test output 198 Chapter 11 Change history Celery Documeniation Release 2 5 5 11 29 2 News e Now depends on carrot version 0 10 7
46. when_bound PBackend consume task_id timeout None PBackend delete_taskset taskset_id PBackend drain_events connection consumer timeout None now lt built in function time gt PBackend get_many task_ids timeout None kwargs PBackend get_task_meta ftask_id cache True PBackend poll task_id backlog_limit 100 PBackend reload_task_result task_id PBackend reload_taskset_result task_id Reload taskset result even if it has been previously fetched PBackend restore_taskset taskset_id cache True PBackend revive channel PBackend save_taskset taskset_id result PBackend supports_native_join True PBackend wait_for task_id timeout None cache True propagate True kwargs exception celery backends amqp BacklogLimitExceeded Too much state history to fast forward 13 6 Internal Module Reference 363 Celery Documentation Release 2 5 5 celery backends amqp repair_uuid s 13 6 26 celery backends mongodb MongoDB backend for celery class celery backends mongodb Bunch kw class celery backends mongodb MongoBackend args kwargs cleanup Delete expired metadata mongodb_database celery mongodb_host localhost mongodb_password None mongodb_port 27017 mongodb_taskmeta_collection celery_taskmeta mongodb_user None process_cleanup 13 6 27 celery backends redis class celery backends redis RedisBackend host None port None
47. Also large parts can be customized without resorting to monkey patching 13 5 1 Examples Creating a Celery instance gt gt gt from celery import Celery gt gt gt celery Celery gt gt gt celery config_from_object celeryconfig gt gt gt celery config_from_envvar CELERY_CONFIG_MODULE Creating tasks celery task def add x y return x y Creating custom Task subclasses Task celery create_task_cls class DebugTask Task abstract l def on_failure self args kwargs import pdb pdb set_trace celery task base DebugTask def add x y return x y Starting a worker worker celery Worker loglevel INFO Getting access to the configuration celery conf CELERY_ALWAYS_EAGER 1 celery conf CELERY_ALWAYS_EAGER 13 5 The Big Instance Refactor 319 Celery Documeniation Release 2 5 5 Controlling workers gt gt gt celery control inspect active gt gt gt celery control rate_limit add name 100 m gt gt gt celery control broadcast shutdown gt gt gt celery control discard_all Other interesting attributes Establish broker connection gt gt gt celery broker_connection AMOP Specific features gt gt gt celery amqp gt gt gt celery amgp Router gt gt gt celery amqp get_queues gt gt gt celery amqp get_task_consumer Loader gt gt gt celery
48. Enables disables colors in logging output by the Celery apps By default colors are enabled if 1 the app is logging to a real terminal and not a file 2 the app is not running on Windows CELERYD_LOG_FORMAT The format to use for log messages Default is asctime s levelname s processName s message s See the Python logging module for more information about log formats 3 2 Configuration Directives 103 Celery Documentation Release 2 5 5 CELERYD_TASK_LOG_FORMAT The format to use for log messages logged in tasks Can be overridden using the loglevel option to celeryd Default is asctime s levelname s processName s task_name s task_id s message s See the Python logging module for more information about log formats CELERY_REDIRECT_STDOUTS If enabled stdout and stderr will be redirected to the current logger Enabled by default Used by celeryd and celerybeat CELERY_REDIRECT_STDOUTS_LEVEL The log level output to stdout and stderr is logged as Can be one of DEBUG INFO WARNING ERROR or CRITICAL Default is WARNING 3 2 21 Security CELERY_SECURITY_KEY New in version 2 5 The relative or absolute path to a file containing the private key used to sign messages when Message Signing is used CELERY_SECURITY_CERTIFICATE New in version 2 5 The relative or absolute path to an X 509 certificate file used to sign messages when Message Signing is used CELERY_SE
49. Optimally certificates should be signed by an official Certificate Authority but they can also be self signed To enable this you should configure the CELERY_TASK_SERIALIZER setting to use the auth serializer Also required is configuring the paths used to locate private keys and certificates on the _ file system the CELERY SECURITY_KEY CELERY _SECURITY_CERTIFICATE and CELERY_SECURITY_CERT_STORE settings respectively With these configured it is also necessary to call the celery security setup_security function Note that this will also disable all insucure serializers so that the worker won t accept messages with untrusted content types This is an example configuration using the auth serializer with the private key and certificate files located in etc ssl CELERY_SECURITY_KEY etc ssl private worker key CELERY_SECURITY_CERTIFICATE etc ssl certs worker pem CELERY_SECURITY_CERT_STORE etc ssl certs pem from celery security import setup_security setup_security Note While relative paths are not disallowed using absolute paths is recommended for these files Also note that the auth serializer won t encrypt the contents of a message so if needed this will have to be enabled separately 2 10 5 Intrusion Detection The most important part when defending your systems against intruders is being a
50. Returns a list of tuple pairs receiver response Raises DispatcherKeyError 13 6 Internal Module Reference 387 Celery Documeniation Release 2 5 5 if any receiver raises an error specifically any subclass of Except ion the error instance is returned as the result for that receiver 13 6 56 celery utils dispatch saferef Safe weakrefs originally from pyDispatcher Provides a way to safely weakref any function including bound methods which aren t handled by the core weakref module class celery utils dispatch saferef BoundMethodWeakref target on_delete None Safe and reusable weak references to instance methods BoundMethodWeakref objects provide a mechanism for referencing a bound method without requiring that the method object itself which is normally a transient object is kept alive Instead the BoundMethodWeakref object keeps weak references to both the object and the function which together define the instance method key the identity key for the reference calculated by the class s calculate_key method applied to the target instance method deletion_methods sequence of callable objects taking single argument a reference to this object which will be called when either the target object or target function is garbage collected i e when this object becomes invalid These are specified as the on_delete parameters of safe_ref calls weak_self weak reference to the target ob
51. SIGINT Ctrl C killed the pool abruptly terminating the currently executing tasks Fixed by making the pool worker processes ignore SIGINT Should not close the consumers before the pool is terminated just cancel the consumers See issue 122 Now depends on billiard gt 0 3 1 celeryd Previously exceptions raised by worker components could stall startup now it correctly logs the excep tions and shuts down celeryd Prefetch counts was set too late QoS is now set as early as possible so celeryd can t slurp in all the messages at start up 11 36 2 Changes celery contrib abortable Abortable tasks Tasks that defines steps of execution the task can then be aborted after each step has completed EventDispatcher No longer creates AMQP channel if events are disabled Added required RPM package names under bdist_rpm section to support building RPMs from the sources using setup py Running unit tests NOSE_VERBOSE environment var now enables verbose output from Nose celery execute apply Pass log file log level arguments as task kwargs See issue 110 celery execute apply Should return exception not Except ionInfo on error 220 Chapter 11 Change history Celery Documeniation Release 2 5 5 See issue 111 e Added new entries to the FAQs Should I use retry or acks_late Can I execute a task by name 11 37 1 0 4 release date 2010 05 31 09 54 A M CEST e Changelog mer
52. The mediator simply moves tasks in the ready_queue over to the task pool for execution using celery worker job TaskRequest execute_using_pool TaskPool This is a slightly modified mult iprocessing Pool It mostly works the same way except it makes sure all of the workers are running at all times If a worker is missing it replaces it with a new one 13 4 Task Messages e Message format e Extensions e Example message e Serialization 13 4 Task Messages 317 Celery Documentation Release 2 5 5 13 4 1 Message format e task string Name of the task required id string Unique id of the task UUID required args list List of arguments Will be an empty list if not provided kwargs dictionary Dictionary of keyword arguments Will be an empty dictionary if not provided retries int Current number of times this task has been retried Defaults to 0 if not specified eta string ISO 8601 Estimated time of arrival This is the date and time in ISO 8601 format If not provided the message is not scheduled but will be executed asap expires string ISO 8601 versionadded 2 0 2 Expiration date This is the date and time in ISO 8601 format If not provided the message will never expire The message will be expired when the message is received and the expiration date has been exceeded 13 4 2 Extensions Extensions are additional keys in the message body that the worker may or may not support
53. django syncdb python celeryinit Note This is only applies if using Django version 1 1 or higher e Now depends on carrot version 0 6 0 e Now depends on python daemon 1 4 8 11 46 2 Important changes e Celery can now be used in pure Python outside of a Django project This means celery is no longer Django specific For more information see the FAQ entry Is Celery for Django only e Celery now supports task retries See Cookbook Retrying Tasks for more information e We now have an AMQP result store backend It uses messages to publish task return value and status And it s incredibly fast See issue 6 for more info e AMQP QoS prefetch count implemented This to not receive more messages than we can handle e Now redirects stdout stderr to the celeryd log file when detached 234 Chapter 11 Change history Celery Documeniation Release 2 5 5 e Now uses inspect getargspec to only pass default arguments the task supports Add Task on_success on_retry on_failure handlers See celery task base Task on_success celery task base Task on_retry celery task base Task on_failure e celery utils gen_unique_id Workaround for http bugs python org issue4607 e You can now customize what happens at worker start at process init etc by creating your own loaders see celery loaders default celery loaders djangoapp celery loaders e Support for multiple AMQP exchanges and queues This feature m
54. exchange_type direct options Creates new option mapping for queue with required keys present format indent 0 indent_first True Format routing table into string for log dumps select_subset wanted create_missing True Select subset of the currently defined queues Does not return anything queues not in wanted will be discarded in place Parameters e wanted List of wanted queue names e create_missing By default any unknown queues will be added automatically but if disabled the occurrence of unknown queues in wanted will raise KeyError classmethod with_defaults queues default_exchange default_exchange_type Alternate constructor that adds default exchange and exchange type information to queues that does not have any 12 3 3 TaskPublisher class celery app amqp TaskPublisher args kwargs auto_declare False declare delay_task task_name task_args None task_kwargs None countdown None eta None task_id None taskset_id None expires None exchange None exchange_type None event_dispatcher None retry None retry_policy None queue None now None retries 0 chord None kwargs Send task message retry False retry policy None 12 4 celery app defaults e celery app defaults j 12 4 1 celery app defaults Configuration introspection and defaults copyright 3 2009 2012 by Ask Solem license BSD see LICENSE for more details class celery app defaults Option de
55. from celery task control import broadcast gt gt gt broadcast rate_limit arguments task_name myapp mytask rate limit 200 m This will send the command asynchronously without waiting for a reply To request a reply you have to use the reply argument 2 4 Workers Guide 45 Celery Documentation Release 2 5 5 gt gt gt broadcast rate_limit task_name myapp mytask T rate_limit 200 m reply Tr rate limit set successfully yrker2 e gt rate limit UC YAE worker3 example rate limit set su yt Using the destination argument you can specify a list of workers to receive the command gt gt gt broadcast gt gt gt broadcast rate_limit task_name myapp mytask rate_limit 200 m reply i destination worker1 example com workerl example com New rate limit set successfully Of course using the higher level interface to set rate limits is much more convenient but there are commands that can only be requested using broadcast Rate limits Example changing the rate limit for the myapp mytask task to accept 200 tasks a minute on all servers gt gt gt from celery task control import rate_limit gt gt gt rate_limit myapp mytask 200 m Example changing the rate limit on a single host by specifying the destination host name gt gt gt rate_limit myapp mytask 200 m destination workerl example com
56. on_decode_error None purge Purge messages from all queues qos prefetch_size 0 prefetch_count 0 apply_global False Specify quality of service The client can request that messages should be sent in advance so that when the client finishes processing a message the following message is already held locally rather than needing to be sent down the channel Prefetching gives a performance improvement The prefetch window is Ignored if the no_ack option is set Parameters e prefetch_size Specify the prefetch window in octets The server will send a message in advance if it is equal to or smaller in size than the available prefetch size and also falls within other prefetch limits May be set to zero meaning no specific limit although other prefetch limits may still apply 356 Chapter 13 Internals Celery Documeniation Release 2 5 5 e prefetch_count Specify the prefetch window in terms of whole mes sages e apply_global Apply new settings globally on all channels Currently not supported by RabbitMQ queues None receive body message Method called when a message is received This dispatches to the registered callbacks Parameters e body The decoded message body e message The Message instance Raises NotImplementedError If no consumer callbacks have been registered recover requeue False Redeliver unacknowledged messages Asks the broker to redeliver all unackno
57. successful wait timeout None worker_pids celery concurrency processes pool DynamicPool alias of Pool class celery concurrency processes pool IMapIterator cache lost_worker_timeout 10 0 next timeout None ready worker_pids 342 Chapter 13 Internals Celery Documeniation Release 2 5 5 class celery concurrency processes pool IMapUnorderedIterator cache lost_worker_timeout 10 0 class celery concurrency processes pool LaxBoundedSemaphore value ver bose None Semaphore that checks that release is lt acquires but ignores if releases gt value clear release class celery concurrency processes pool MapResult cache chunksize length callback accepted worker_pids exception celery concurrency processes pool MaybeEncodingError exc value Wraps unpickleable object class celery concurrency processes pool Pool processes None initializer None ini targs maxtasksperchild None timeout None soft_timeout None force_execv False Class which supports an async version of the apply builtin class Process args kwargs class Pool ResultHandler outqueue get cache poll join_exited_workers putlock body exception Pool SoftTimeLimitExceeded The soft time limit has been exceeded This exception is raised to give the task a chance to clean up class Pool Supervisor pool body class Pool TaskHandler taskqueue put outqueue pool
58. 11 38 4 Fixes e Mediator thread no longer blocks for more than 1 second With rate limits enabled and when there was a lot of remaining time the mediator thread could block shutdown and potentially block other jobs from coming in e Remote rate limits was not properly applied Issue 98 e Now handles exceptions with Unicode messages correctly in TaskRequest on_failure e Database backend TaskMeta result default value should be None not empty string 11 39 1 0 2 release date 2010 03 31 12 50 P M CET e Deprecated CELERY_BACKEND please use CELERY_RESULT_BACKEND instead 224 Chapter 11 Change history Celery Documeniation Release 2 5 5 e We now use a custom logger in tasks This logger supports task magic keyword arguments in formats The default format for tasks CELERYD_TASK_LOG_FORMAT now includes the id and the name of tasks so the origin of task log messages can easily be traced Example output 2010 03 25 13 11 20 317 INFO PoolWorker 1 tasks add a6e 1 c5ad 60d9 42a0 8b24 9e39363125a4 Hello from add To revert to the previous behavior you can set CELERYD_TASK_LOG_FORMAT s asctime s levelname s processName s message s nun strip e Unit tests Don t disable the django test database tear down instead fixed the underlying issue which was caused by modifications to the DATABASE_NAME setting Issue 82 e
59. 2 User Guide Celery Documeniation Release 2 5 5 The target function e args Positional arguments e kwargs Keyword arguments Logging Signals setup_logging Celery won t configure the loggers if this signal is connected so you can use this to completely override the logging configuration with your own If you would like to augment the logging configuration setup by Celery then you can use the after_setup_logger and after_setup_task_logger signals Provides arguments e loglevel The level of the logging object e logfile The name of the logfile e format The log format string e colorize Specify if log messages are colored or not after_setup_logger Sent after the setup of every global logger not task loggers Used to augment logging configuration Provides arguments e logger The logger object e loglevel The level of the logging object e logfile The name of the logfile e format The log format string e colorize Specify if log messages are colored or not after_setup_task_logger Sent after the setup of every single task logger Used to augment logging configuration Provides arguments e logger The logger object e loglevel The level of the logging object e logfile The name of the logfile e format The log format string e colorize Specify if log messages are colored or not 2 13 Signals 85 Celery Documeniation Release 2 5 5 86 Chapter 2 User Guide CHAPTER 3 Confi
60. AMOPBackend Consumer channel queues None no_ack None auto_declare None call backs None on_decode_error None Message consumer Parameters e channel see channel e queues see queues e no_ack see no_ack e auto_declare see auto_declare e callbacks see callbacks e on_decode_error see on_decode_error add_queue queue auto_declare True 13 6 Internal Module Reference 355 Celery Documentation Release 2 5 5 callbacks None cancel End all active queue consumers This does not affect already delivered messages but it does mean the server will not send any more messages for this consumer cancel _by queue queue Cancel consumer by queue name channel None close End all active queue consumers This does not affect already delivered messages but it does mean the server will not send any more messages for this consumer connection consume no_ack None consuming_from queue declare Declare queues exchanges and bindings This is done automatically at instantiation if auto_declare is set flow active Enable disable flow from peer This is a simple flow control mechanism that a peer can use to avoid overflowing its queues or otherwise finding itself receiving more messages than it can process The peer that receives a request to stop sending content will finish sending the current content if any and then wait until flow is reactivated no_ack None
61. AMQP Command specification Used to convert arguments to Python values and display various help and tooltips Parameters 12 37 celery bin camqadm 305 Celery Documentation Release 2 5 5 e args see args e returns see returns coerce index value Coerce value for argument at index E g if args is is_active bool gt gt gt 0 False False format_arg name type default_value None format_response response Format the return value of this command in a human friendly way format_signature str_args_to_python argiist Process list of string arguments to values according to spec e g gt gt gt spec Spec queue if_unused 1 gt gt gt spec str_args_to_python pobox true pobox True celery bin camqadm camqadm args options celery bin camqadm dump_message message celery bin camqadm format_declare_queue ret celery bin camqadm main celery bin camgqadm say m 12 38 celery bin celeryd_multi 12 38 1 Examples wt st U se Se HE HR Single worker with explicit name and events enabled celeryd multi start Leslie E Pidfiles and logfiles are stored in the current directory by default Us pidfile and logfile argument to change this The abbreviation n will be expanded to the current node name celeryd multi start Lesli E pidfile var run celery n pid logfile var log celery n log
62. Base Base info on_error None queue Pool Pool Pool Pool Pool Pool Pool Pool Pool Pool Pool Pool Pool Pool Pool Pool Pool Timer Timer Timer Timer Timer Timer Timer Timer Timer Timer Timer Timer Timer Timer Timer Timer Timer BasePool active apply after msecs fun args kwargs priority 0 apply _at eta fun args kwargs priority 0 apply entry entry apply_interval msecs fun args kwargs priority 0 cancel tref clear empty ensure_started enter entry eta priority None enter_after msecs entry priority 0 exit_after msecs priority 10 next on_tick None queue run running False stop BasePool apply_asyne target args kwargs options Equivalent of the apply built in function Base Base Base Base Base Base Base Base Callbacks should optimally return as soon as possible since otherwise the thread which handles the result will get blocked Pool Pool Pool Pool Pool info on_start on_stop Pool is_green False set to true if pool uses greenlets Pool num_processes Pool on_apply args kwargs on_terminate requires_mediator False set to true if pool requires the use of a mediator thread e g if applying new items can block the current thread BasePool rest
63. BaseTask subtask args kwargs Returns subt ask object for this task wrapping arguments and execution options for a single task invo cation BaseTask time_limit None Hard time limit Defaults to the CELERY_TASK_TIME_LIMIT setting BaseTask track_started False If enabled the task will report its status as started when the task is executed by a worker Disabled by default as the normal behaviour is to not report that level of granularity Tasks are either pending finished or waiting to be retried Having a started status can be useful for when there are long running tasks and there is a need to report which task is currently running The application default can be overridden using the CELERY_TRACK_STARTED setting BaseTask type regular The type of task no longer used BaseTask update_state task_id None state None meta None Update task state Parameters e task_id Id of the task to update e state New state str e meta State metadata dict 12 3 celery app amqp AMQ related functionality copyright 3 2009 2012 by Ask Solem license BSD see LICENSE for more details e AMQP Queues e TaskPublisher 12 3 celery app amqp 255 Celery Documentation Release 2 5 5 12 3 1 AMQP class celery app amqp AM P app BrokerConnection Broker connection class used Default is kombu connection BrokerConnection Consumer
64. Chapter 12 API Reference Celery Documeniation Release 2 5 5 e args positional arguments passed on to the task e kwargs keyword arguments passed on to the task e throw Re raise task exceptions Defaults to the CELERY_EAGER_PROPAGATES_EXCEPTIONS setting atype celery result EagerResult classmethod BaseTask apply_async args None kwargs None task_id None publisher None connection None router None queues None options Apply tasks asynchronously by sending a message Parameters e args The positional arguments to pass on to the task a List or tuple e kwargs The keyword arguments to pass on to the task a dict countdown Number of seconds into the future that the task should execute Defaults to immediate execution do not confuse with the immediate flag as they are unrelated e eta A datetime object describing the absolute time and date of when the task should be executed May not be specified if countdown is also supplied Do not confuse this with the immediate flag as they are unrelated e expires Either a int describing the number of seconds or a datetime object that describes the absolute time and date of when the task should expire The task will not be executed after the expiration time e connection Re use existing broker connection instead of establishing a new one e retry If enabled sending of the task message will be retried in
65. Django Loader New config CELERY_DB_REUSE_MAX max number of tasks to reuse the same database connection The default is to use a new connection for every task We would very much like to reuse the connec tion but a safe number of reuses is not known and we don t have any way to handle the errors that might happen which may even be database dependent See http bit ly 94fwdd e celeryd The worker components are now configurable CELERYD_POOL CELERYD_CONSUMER CELERYD_MEDIATOR and CELERYD_ETA_SCHEDULER The default configuration is as follows ERYD_POOL celery concurrency processes TaskPool 1ERYD_MEDIATOR celery worker controllers Mediator ELERYD_ETA_SCHEDULER celery worker controllers ScheduleController ELERYD_CONSUMER celery worker consumer Consumer QARA H BH H B The CELERYD_POOL setting makes it easy to swap out the multiprocessing pool with a threaded pool or how about a twisted eventlet pool Consider the competition for the first pool plug in started e Debian init scripts Use a not amp amp Issue 82 e Debian init scripts Now always preserves CELERYD_OPTS from the etc default celeryd and etc default celerybeat e celery beat Scheduler Fixed a bug where the schedule was not properly flushed to disk if the schedule had not been properly initialized e celerybeat
66. Fixed a bug where unicode in stdout redirected log messages couldn t be written Issue 522 11 11 2 4 0 release date 2011 11 04 04 00 P M GMT by Ask Solem 11 11 1 Important Notes e Now supports Python 3 e Fixed deadlock in worker process handling Issue 496 A deadlock could occur after spawning new child processes because the logging library s mutex was not properly reset after fork The symptoms of this bug affecting would be that the worker simply stops processing tasks as none of the workers child processes are functioning There was a greater chance of this bug occurring with maxtasksperchild ora time limit enabled This is a workaround for http bugs python org issue672 1 msg 140215 Be aware that while this fixes the logging library lock there could still be other locks initialized in the parent process introduced by custom code Fix contributed by Harm Verhagen e AMQP Result backend Now expires results by default The default expiration value is now taken from the CELERY_TASK_RESULT_EXPIRES setting The old CELERY_AMOQP_TASK_RESULT_EXPIRES setting has been deprecated and will be re moved in version 3 0 Note that this means that the result backend requires RabbitMQ 1 1 0 or higher and that you have to disable expiration if you are running with an older version You can do so by disabling the CELERY_TASK_RESULT_EXPIRES setting
67. Movsisyan github https github com mher Steeve Morin github https github com steeve twitter http twitter com steeve 6 8 Contacts 129 Celery Documentation Release 2 5 5 6 8 2 Website The Celery Project website is run and maintained by Mauro Rocco github https github com fireantology twitter https twitter com fireantology with design by Jan Henrik Helmers web http www helmersworks com twitter http twitter com helmers 6 9 Packages 6 9 1 celery git https github com celery celery CI http travis ci org ask celery PyPI http pypi python org pypi celery docs http docs celeryproject org 6 9 2 kombu Messaging framework git https github com celery kombu CI http travis ci org ask kombu PyPI http pypi python org pypi kombu docs http kombu readthedocs org 6 9 3 billiard Fork of multiprocessing containing improvements that will eventually be merged into the Python stdlib git https github com celery billiard PyPI http pypi python org pypi billiard 130 Chapter 6 Contributing Celery Documeniation Release 2 5 5 6 9 4 librabbitmq Very fast Python AMQP client written in C git https github com celery librabbitmq PyPI http pypi python org pypi librabbitmq 6 9 5 celerymon Celery monitor web service git https github com celery celerymon PyPI http pypi python org pypi celerymon 6 9 6 django celery Django lt gt Cel
68. None options celery worker job execute_and_ trace name uuid args kwargs request None opts This is a pickleable method used as a target when applying to pools It s the same as gt gt gt trace_task name args kwargs 0 13 6 5 celery worker mediator e celery worker mediator j celery worker mediator The mediator is an internal thread that moves tasks from an internal Queue to the worker pool This is only used if rate limits are enabled as it moves messages from the rate limited queue which holds tasks that are allowed to be processed to the pool Disabling rate limits will also disable this machinery and can improve performance 13 6 Internal Module Reference 333 Celery Documentation Release 2 5 5 copyright 3 2009 2012 by Ask Solem license BSD see LICENSE for more details class celery worker mediator Mediator ready_queue callback logger None app None body callback None Callback called when a task is obtained move ready_queue None The task queue a Queue instance class celery worker mediator WorkerComponent w kwargs create w include_if w name mediator namespace worker requires pool queues 13 6 6 celery worker buckets e celery worker buckets j celery worker buckets This module implements the rate limiting of tasks by having a token bucket queue for each task type When a task is allow
69. Parameters task_registry The task registry used to get the task type class for a given task name add_bucket_for_type fask_name Add a bucket for a task type Will read the tasks rate limit and create a TokenBucket Queue if it has one If the task doesn t have a rate limit Fast Queue will be used instead clear Delete the data in all of the buckets empty Returns True if all of the buckets are empty get block True timeout None Retrive the task from the first available bucket Available as in there is an item in the queue and you can consume tokens from it get_bucket_for_type fask_name Get the bucket for a particular task type get_nowait init_with_registry Initialize with buckets for all the task types in the registry items Flattens the data in all of the buckets into a single list put request Put a Request into the appropiate bucket put_nowait request Put a Request into the appropiate bucket qsize Get the total size of all the queues refresh Refresh rate limits for all task types in the registry update_bucket_for_type task_name 13 6 Internal Module Reference 335 Celery Documentation Release 2 5 5 class celery worker buckets TokenBucketQueue fill_rate queue None capacity 1 Queue with rate limited get operations This uses the token bucket algorithm to rate limit the queue on get operations Parameters e fill_rate The rate in tokens secon
70. The original exception instance on_task task Handle received task 13 6 Internal Module Reference 329 Celery Documentation Release 2 5 5 If the task has an eta we enter it into the ETA schedule otherwise we move it the ready queue for imme diate processing pidbox_node None The process mailbox kombu pidbox node pool None The current worker pool instance priority timer None A timer used for high priority internal tasks such as sending heartbeats ready_queue None The queue that holds tasks ready for immediate processing receive_message body message Handles incoming messages Parameters e body The message body e message The kombu message object reset_connection Re establish the broker connection and set up consumers heartbeat and the event dispatcher reset_pidbox_node Sets up the process mailbox restart_heartbeat Restart the heartbeat thread This thread sends heartbeat events at intervals so monitors can tell if the worker is off line missing send_events False Enable disable events start Start the consumer Automatically survives intermittent connection failure and will retry establishing the connection and restart consuming messages stop Stop consuming Does not close the broker connection so be sure to call close_connection when you are finished with it stop_consumers close_connection True Stop consuming tasks and broadcast com
71. This is a known issue on Windows You have to start celeryd with the command python m celeryd bin celeryd Any additional arguments can be appended to this command See http bit ly bo9RSw 9 9 2 The B beat option to celeryd doesn t work Answer That s right Run celerybeat and celeryd as separate services instead 9 9 3 django celery can t find settings Answer You need to specify the settings argument to manage py python manage py celeryd start settings settings See http bit ly bo9RSw 160 Chapter 9 Frequently Asked Questions CHAPTER 10 What s new in Celery 2 5 Celery aims to be a flexible and reliable best of breed solution to process vast amounts of messages in a distributed fashion while providing operations with the tools to maintain such a system Celery has a large and diverse community of users and contributors you should come join us on IRC or our mailing list To read more about Celery you should visit our website While this version is backward compatible with previous versions it is important that you read the following section If you use Celery in combination with Django you must also read the django celery changelog and upgrade to django celery 2 5 This version is officially supported on CPython 2 5 2 6 2 7 3 2 and 3 3 as well as PyPy and Jython e Important Notes Broker connection pool now enabled by default AMQP Result Backend Exchange is no lo
72. Use the routing settings from a queue defined in CELERY_QUEUES If defined the exchange and routing_key options will be ignored Task exchange Override the global default exchange for this task Task routing_key Override the global default routing_key for this task Task mandatory If set the task message has mandatory routing By default the task is silently dropped by the broker if it can t be routed to a queue However If the task is mandatory an exception will be raised instead Not supported by amaplib Task immediate Request immediate delivery If the task cannot be routed to a task worker immediately an exception will be raised This is instead of the default behavior where the broker will accept and queue the task but with no guarantee that the task will ever be executed Not supported by amaplib Task priority The message priority A number from 0 to 9 where 0 is the highest priority Not supported by RabbitMQ See also Routing options for more information about message options and Routing Tasks 24 Chapter 2 User Guide Celery Documeniation Release 2 5 5 2 2 6 Task names The task type is identified by the task name If not provided a name will be automatically generated using the module and class name For example gt gt gt task name sum of two numbers gt gt gt def add x y return x y gt gt gt add name sum of two numbers Th
73. a message describing the reason 152 Chapter 9 Frequently Asked Questions Celery Documeniation Release 2 5 5 9 3 5 Does it work on FreeBSD Answer The multiprocessing pool requires a working POSIX semaphore implementation which isn t enabled in FreeBSD by default You have to enable POSIX semaphores in the kernel and manually recompile multiprocessing Luckily Viktor Petersson has written a tutorial to get you started with Celery on FreeBSD here http www playingwithwire com 2009 10 how to get celeryd to work on freebsd 9 3 6 I m having ntegrityError Duplicate Key errors Why Answer See MySQL is throwing deadlock errors what can I do Thanks to howsthedotcom 9 3 7 Why aren t my tasks processed Answer With RabbitMQ you can see how many consumers are currently receiving tasks by running the following command rabbitmqctl list_queues p lt myvhost gt name messages consumers Listing queues celery 2891 2 This shows that there s 2891 messages waiting to be processed in the task queue and there are two consumers pro cessing them One reason that the queue is never emptied could be that you have a stale worker process taking the messages hostage This could happen if celeryd wasn t properly shut down When a message is received by a worker the broker waits for it to be acknowledged before marking the message as processed The broker will not re send that message to another consumer until the consum
74. a single task instance 9 2 2 Is Celery for Django only Answer No Celery does not depend on Django anymore To use Celery with Django you have to use the django celery package 9 2 3 Do I have to use AMQP RabbitMQ Answer No You can also use Redis Beanstalk CouchDB MongoDB or an SQL database see Using other queues These virtual transports may have limited broadcast and event functionality For example remote control commands only works with AMQP and Redis 9 1 General 151 Celery Documentation Release 2 5 5 Redis or a database won t perform as well as an AMQP broker If you have strict reliability requirements you are encouraged to use RabbitMQ or another AMQP broker Redis database also use polling so they are likely to consume more resources However if you for some reason are not able to use AMQP feel free to use these alternatives They will probably work fine for most use cases and note that the above points are not specific to Celery If using Redis database as a queue worked fine for you before it probably will now You can always upgrade later if you need to 9 2 4 Is Celery multilingual Answer Yes celeryd is an implementation of Celery in Python If the language has an AMQP client there shouldn t be much work to create a worker in your language A Celery worker is just a program connecting to the broker to process messages Also there s another way to be language independent and
75. akismet verify_key raise ImproperlyConfigured Invalid AKISMET_KEY is_spam akismet comment_check user_ip remote_addr comment_content comment comment comment_author comment name comment_author_email comment email_address if is_spam comment is_spam comment save return is_spam 2 3 Executing Tasks e Basics ETA and countdown e Expiration e Serializers e Connections and connection timeouts e Routing options e AMQP options 2 3 1 Basics Executing a task is done with apply_async and the shortcut delay delay is simple and convenient as it looks like calling a regular function 2 3 Executing Tasks 37 Celery Documentation Release 2 5 5 Task delay argl arg2 kwargl x kwarg2 y The same using apply_async is written like this Task apply_async args argl arg2 kwargs kwargl x kwarg2 y While delay is convenient it doesn t give you as much control as using apply_async With apply_async you can override the execution options available as attributes on the Task class see Task options In addition you can set countdown eta task expiry provide a custom broker connection and more Let s go over these in more detail All the examples uses a simple task called add returning the sum of two positional arguments task def add x y return x y Note You can also execute a task by name using send_task if you don t have
76. as soon as possible No tasks should be lost You should never stop celeryd with the KILL signal 9 unless you ve tried TERM a few times and waited a few minutes to let it get a chance to shut down As if you do tasks may be terminated mid execution and they will not be re run unless you have the acks_late option set Task acks_late CELERY_ACKS_LATE See also Stopping the worker 9 7 Tasks 159 Celery Documeniation Release 2 5 5 9 7 18 How do I run celeryd in the background on platform Answer Please see Running celeryd as a daemon 9 8 Django 9 8 1 What purpose does the database tables created by django celery have Several database tables are created by default these relate to e Monitoring When you use the django admin monitor the cluster state is written to the TaskState and WorkerState models e Periodic tasks When the database backed schedule is used the periodic task schedule is taken from the PeriodicTask model there are also several other helper tables IntervalSchedule CrontabSchedule PeriodicTasks e Task results The database result backend is enabled by default when using django celery this is for historical reasons and thus for backward compatibility The results are stored in the TaskMeta and TaskSetMeta models these tables are not created if another result backend is configured 9 9 Windows 9 9 1 celeryd keeps spawning processes at startup Answer
77. be cleaned automatically based on the CELERY_TASK_RESULT_EXPIRES setting By de fault this is set to expire after 1 day if you have a very busy cluster you should lower this value For a list of options supported by the AMQP result backend please see AMQP backend settings Database Result Backend Keeping state in the database can be convenient for many especially for web applications with a database already in place but it also comes with limitations e Polling the database for new states is expensive and so you should increase the polling intervals of operations such as result wait and tasksetresult join e Some databases use a default transaction isolation level that is not suitable for polling tables for changes In MySQL the default transaction isolation level is REPEATABLE READ which means the transaction will not see changes by other transactions until the transaction is committed It is recommended that you change to the READ COMMITTED isolation level Built in States PENDING Task is waiting for execution or unknown Any task id that is not known is implied to be in the pending state STARTED Task has been started Not reported by default to enable please see Task track_started metadata pid and hostname of the worker process executing the task SUCCESS Task has been successfully executed metadata result contains the return value of the task propagates Yes ready Yes FAILURE Task execution
78. celery registry j 12 22 1 celery registry Registry of available tasks copyright 3 2009 2012 by Ask Solem license BSD see LICENSE for more details class celery registry TaskRegistry exception NotRegistered The task is not registered TaskRegistry filter_types type Return all tasks of a specific type TaskRegistry periodic Get all periodic task types askRegistry pop key args TaskRegistry register task Register a task in the task registry The task will be automatically instantiated if not already an instance TaskRegistry regular Get all regular task types TaskRegistry unregister name Unregister task by name Parameters name name of the task to unregister ora celery task base Task witha valid name attribute Raises celery exceptions NotRegistered if the task has not been registered celery registry tasks celery chord_unlock lt task celery chord_unlock gt celery backend_cleanup lt task cel Global task registry e celery states States Sets x READY_STATES UNREADY_STATES EXCEPTION_STATES x PROPAGATE STATES ALL_STATES Misc 286 Chapter 12 API Reference Celery Documeniation Release 2 5 5 12 23 celery states Built in Task States 12 23 1 States See Task States 12 23 2 Sets READY_STATES Set of states meaning the task result is ready has been executed UNREADY_STATES Set of states
79. celery task meta taskset_keyprefix celery taskset meta celery backends base unpickle_backend cls args kwargs Returns an unpickled backend 13 6 23 celery backends database class celery backends database DatabaseBackend dburi None expires None en gine_options None kwargs The database result backend ResultSession cleanup Delete expired metadata subpolling_interval 0 5 354 Chapter 13 Internals Celery Documeniation Release 2 5 5 13 6 24 celery backends cache class celery backends cache CacheBackend expires None backend None options kwargs client delete key get key mget keys on_chord_apply setid body result None kwargs on_chord_part_return task propagate False servers None set key value supports_native_join True class celery backends cache DummyClient args kwargs ce ce delete key args kwargs get key args kwargs get_multi keys incr key delta set key value args kwargs lery backends cache get_best_memcache args kwargs lery backends cache import_best_memcache 13 6 25 celery backends amqp class celery backends amgqp AMQPBackend connection None exchange None ex change_type None persistent None serializer None auto_delete True kwargs Publishes results by sending messages exception Back logLimitExceeded Too much state history to fast forward class
80. celeryctl must be configured for that to work The daemonization cookbook contains examples Contributed by Jude Nagurney The MongoDB result backend can now use Replica Sets Contributed by Ivan Metzlar gevent Now supports autoscaling Issue 599 Contributed by Mark Lavin multiprocessing Mediator thread is now always enabled even though rate limits are disabled as the pool semaphore is known to block the main thread causing broadcast commands and shutdown to depend on the semaphore being released 10 5 Fixes Exceptions that are re raised with a new exception object now keeps the original stack trace Windows Fixed the no handlers found for multiprocessing warning Windows The celeryd program can now be used Previously Windows users had to launch celeryd using python m celery bin celeryd Redis result backend Now uses SETEX command to set result key and expiry atomically Suggested by yaniv aknin celeryd Fixed a problem where shutdown hanged when Ctrl C was used to terminate celeryd No longer crashes when channel errors occur Fix contributed by Roger Hu 10 5 Fixes 167 Celery Documentation Release 2 5 5 Fixed memory leak in the eventlet pool caused by the use of greenlet getcurrent Fix contributed by Ignas Mikalajnas Cassandra backend No longer uses pycassa connect which is deprecated since pycassa 1 4 Fix contributed by Jeff Terrace Fixed unicode decode errors that c
81. cluster it is important to know how RabbitMQ can be monitored RabbitMQ ships with the rabbitmqctl 1 command with this you can list queues exchanges bindings queue lengths the memory usage of each queue as well as manage users virtual hosts and their permissions Note The default virtual host is used in these examples if you use a custom virtual host you have to add the p argument to the command e g rabbitmqctl list_queues p my_vhost Inspecting queues Finding the number of tasks in a queue rabbitmqctl list_queues name messages messages_ready messages_unacknowledged Here messages_ready is the number of messages ready for delivery sent but not received messages_unacknowledged is the number of messages that has been received by a worker but not acknowledged yet meaning it is in progress or has been reserved messages is the sum of ready and unacknowledged messages Finding the number of workers currently consuming from a queue rabbitmgqctl list_queues name consumers Finding the amount of memory allocated to a queue rabbitmqctl list_queues name memory Tip Adding the q option to rabbitmqctl 1 makes the output easier to parse 2 9 4 Redis If you re using Redis as the broker you can monitor the Celery cluster using the redis cli 1 command to list lengths of queues Inspecting queues Finding the number of tasks in a queue redis cli h HOST p PORT n DATABASE NUMBER l
82. db None password None expires None max_connections None kwargs Redis task result store client db 0 default Redis db number 0 delete key get key host localhost default Redis server hostname localhost max_connections None Maximium number of connections in the pool mget keys on_chord_apply setid body result None kwargs on_chord_part_return task propagate False password None default Redis password None port 6379 default Redis server port 6379 redis None redis py client module 364 Chapter 13 Internals Celery Documeniation Release 2 5 5 set key value supports_native_join True 13 6 28 celery backends cassandra celery backends cassandra class celery backends cassandra CassandraBackend servers None keyspace None column_family None cas sandra_options None de tailed_mode False kwargs Highly fault tolerant Cassandra backend servers List of Cassandra servers with format hostname port Raises celery exceptions ImproperlyConfigured if module pycassa is not available column_family None detailed_mode False keyspace None process_cleanup servers 13 6 29 celery backends tyrant celery backends tyrant class celery backends tyrant TyrantBackend tyrant_host None tyrant_port None kwargs Tokyo Cabinet based task backend store tyrant_host The hostname to the Tokyo Tyrant server tyrant_port The
83. dler removeHandler 11 30 4 Experimental e celeryd multi Added daemonization support celeryd multi can now be used to start stop and restart worker nodes celeryd multi start jerry elaine george kramer This also creates PID files and log files celeryd jerry pid celeryd jerry log To specify a location for these files use the pidfile and logfile arguments with the n format celeryd multi start jerry elaine george kramer logfile var log celeryd n log pidfile var run celeryd n pid Stopping celeryd multi stop jerry elaine george kramer Restarting The nodes will be restarted one by one as the old ones are shutdown celeryd multi restart jerry elaine george kramer Killing the nodes WARNING Will discard currently executing tasks celeryd multi kill jerry elaine george kramer See celeryd multi help for help e celeryd multi start command renamed to show celeryd multi start will now actually start and detach worker nodes To just generate the commands you have to use celeryd multi show e celeryd Added pidfile argument The worker will write its pid when it starts The worker will not be started if this file exists and the pid contained is still alive e Added generic init d script using celeryd multi 11 30 2 1 0 205 Celery Documentation Release 2 5 5 http github com celery celery tree master contrib generic init d celeryd 11 30 5 Documentation e
84. easy_install U Celery Bundles Celery also defines a group of bundles that can be used to install Celery and the dependencies for a given feature The following bundles are available celery with redis for using Redis as a broker celery with mongodb for using MongoDB as a broker django celery with redis for Django and using Redis as a broker django celery with mongodb for Django and using MongoDB as a broker bundle celery convenience bundle installing Celery and related packages Downloading and installing from source Download the latest version of Celery from http pypi python org pypi celery You can install it by doing the following tar xvfz celery 0 0 0 tar gz cd celery 0 0 0 python setup py build python setup py install as root Using the development version You can clone the repository by doing the following git clone git github com celery celery git 1 2 Brokers Release 2 5 Date February 04 2014 Celery supports several message transport alternatives 6 Chapter 1 Getting Started Celery Documeniation Release 2 5 5 1 2 1 Using RabbitMQ e Installation amp Configuration e Installing the RabbitMQ Server Setting up RabbitMQ Installing RabbitMQ on OS X x Configuring the system host name Starting Stopping the RabbitMQ server Installation amp Configuration RabbitMQ is the default broker so it does not require any additional dependencies or initial co
85. fields Process task event task_types Returns a list of all seen task types tasks_by timestamp limit None Get tasks by timestamp Returns a list of uuid task tuples tasks_by_ type name limit None Get all tasks by type Returns a list of uuid task tuples 294 Chapter 12 API Reference Celery Documeniation Release 2 5 5 tasks_by_ worker hostname limit None Get all tasks by worker Returns a list of uuid task tuples worker_event type fields Process worker event class celery events state Task fields Task State info fields None extra Information about this task suitable for on screen display merge state timestamp fields Merge with out of order event merge_rules RECEIVED name args kwargs retries eta expires How to merge out of order events Disorder is detected by logical ordering e g task received must have happened before a task failed event A merge rule consists of a state and a list of fields to keep from that state RECEIVED name args means the name and args fields are always taken from the RECEIVED state and any values for these fields received before or after is simply ignored on_failed timestamp None fields Callback for the task failed event on_received timestamp None fields Callback for the task received event on_retried timestamp None fields Callb
86. for a long time New settings variable CELERY_TASK_RESULT_EXPIRES Time in seconds or a datetime timedelta ob ject for when after stored task results are deleted For the moment this only works for the database backend celeryd now emits a debug log message for which periodic tasks has been launched The periodic task table is now locked for reading while getting periodic task status MySQL only so far seeking patches for other engines A lot more debugging information is now available by turning on the DEBUG log level loglevel DEBUG Functions methods with a timeout argument now works correctly New celery strategy even_time_distribution With an iterator yielding task args kwargs tuples evenly dis tribute the processing of its tasks throughout the time window available Log message Unknown task ignored now has log level ERROR Log message Got task from broker is now emitted for all tasks even if the task has an ETA estimated time of arrival Also the message now includes the ETA for the task if any Acknowledgement now happens in the pool callback Can t do ack in the job target as it s not pickleable can t share AMQP connection etc Added note about delay hanging in README Tests now passing in Django 1 1 236 Chapter 11 Change history Celery Documeniation Release 2 5 5 e Fixed discovery to make sure app is in INSTALLED_APPS e Previously overridden pool behavior process r
87. format None colorize None task_name None task_id None propagate False app None kwargs Setup the task logger If logfile is not specified then sys stderr is used Returns logger object supports_color logfile None class celery log LoggingProxy logger loglevel None Forward file object to Logging Logger instance Parameters e logger The logging Logger instance to forward to e loglevel Loglevel to use when writing messages close When the object is closed no write requests are forwarded to the logging object anymore closed False fileno flush This object is not buffered so any flush requests are ignored isatty Always returns False Just here for file support loglevel 40 mode w name None write data writelines sequence writelines sequence_of_strings gt None Write the strings to the file The sequence can be any iterable object producing strings This is equivalent to calling write for each string class celery log SilenceRepeated action max_iterations 10 Only log action every n iterations celery log mlevel level 13 6 39 celery events snapshot e celery events snapshot j 372 Chapter 13 Internals Celery Documeniation Release 2 5 5 celery events snapshot Consuming the events as a stream is not always suitable so this module implements a system to take snapshots of the state of a cluster at regular intervals There is a full
88. how often the task is run its interval it can be a timedelta object a crontab object or an integer specifying the time in seconds relative If set to True run times are relative to the time when the server was started This was the previous behaviour periodic tasks are now scheduled by the clock Raises NotImplementedError if the run_every attribute is not defined Example gt gt gt from celery task import tasks PeriodicTask gt gt gt from datetime import timedelta gt gt gt class EveryThirtySecondsTask PeriodicTask run_every timedelta seconds 30 def run self kwargs logger selt get_logger kwargs logger info Execute every 30 seconds gt gt gt from celery task import PeriodicTask gt gt gt from celery schedules import crontab gt gt gt class EveryMondayMorningTask PeriodicTask run_every crontab hour 7 minute 30 day_of_week 1 def run self kwargs logger self get_logger kwargs logger info Execute every Monday at 7 30AM gt gt gt class EveryMorningTask PeriodicTask run_every crontab hours 7 minute 30 def run self kwargs logger L get_logger kwargs logger info Execute every day at 7 30AM gt gt gt class EveryQuarterPastTheHourTask PeriodicTask run_every crontab minute 15 def run s xkwargs logger self get_logger kwargs logger info Execute every 0 15 past the hour every day is_due last
89. image at http code google com p git osx installer downloads list can 3 When git is installed you can finally clone the repository storing it at the 101 location 1 2 Brokers 7 Celery Documentation Release 2 5 5 git clone git github com mxcl homebrew lol Brew comes with a simple utility called brew used to install remove and query packages To use it you first have to add it to PATH by adding the following line to the end of your profile export PATH lol bin lol sbin SPATH Save your profile and reload it source profile Finally we can install rabbitmq using brew brew install rabbitmq Configuring the system host name If you re using a DHCP server that is giving you a random host name you need to permanently configure the host name This is because RabbitMQ uses the host name to communicate with nodes Use the scutil command to permanently set your host name sudo scutil set HostName myhost local Then add that host name to etc hosts so it s possible to resolve it back into an IP address T275 04041 localhost myhost myhost local If you start the rabbitmq server your rabbit node should now be rabbit myhost as verified by rabbitmqctl sudo rabbitmqctl status Status of node rabbit myhost running_applications rabbit RabbitMO 1 7 1 mnesia MNESIA CXC 138 12 4 4 12 fos_mon CPO CXC 138 46 2 2 4 Ssasl SASH CXC 138 TL 2a 1u OM ys stdlib ERT
90. information on how to make the broker connection more trusthworthy The first line of defence should be to put a firewall in front of the broker allowing only white listed machines to access it Keep in mind that both firewall misconfiguration and temproraily disabling the firewall is common in the real world Solid security policy includes monitoring of firewall equipment to detect if they have been disabled be it accidentally or on purpose In other words one should not blindly trust the firewall either If your broker supports fine grained access control like RabbitMQ this is something you should look at enabling See for example http www rabbitmg com access control html Client In Celery client refers to anything that sends messages to the broker e g web servers that apply tasks Having the broker properly secured doesn t matter if arbitrary messages can be sent through a client Need more text here Worker The default permissions of tasks running inside a worker are the same ones as the privileges of the worker itself This applies to resources such as memory file systems and devices An exception to this rule is when using the multiprocessing based task pool which is currently the default In this case the task will have access to any memory copied as a result of the fork call does not apply under MS Windows and access to memory contents written by parent tasks in the same worker child process Limit
91. interval None Backend optimized version of iterate New in version 2 2 Note that this does not support collecting the results for different task types using different backends This is currently only supported by the AMQP Redis and cache result backends iterate timeout None propagate True interval 0 5 Iterate over the return values of the tasks as they finish one by one Raises The exception if any of the tasks raised an exception join timeout None propagate True interval 0 5 Gathers the results of all tasks as a list in order Note This can be an expensive operation for result store backends that must resort to polling e g database You should consider using join_native if your backend supports it Warning Waiting for tasks within a task may lead to deadlocks Please see Avoid launching syn chronous subtasks Parameters e timeout The number of seconds to wait for results before the operation times out e propagate If any of the tasks raises an exception the exception will be re raised e interval Time to wait in seconds before retrying to retrieve a result from the set Note that this does not have any effect when using the AMQP result store backend as it does not use polling Raises celery exceptions TimeoutError if timeout is not None and the operation takes longer than timeout seconds join_native timeout None propagate True interval 0 5 Backend optimized version of joi
92. loader Default backend gt gt gt celery backend As you can probably see this really opens up another dimension of customization abilities 13 5 2 Deprecations e celery task ping celery task PingTask Inferior to the ping remote control command Will be removed in Celery 2 3 13 5 3 Removed deprecations e celery utils timedelta_seconds Use celery utils timeutils timedelta_seconds e celery utils defaultdict Use celery utils compat defaultdict e celery utils all Use celery utils compat all e celery task apply_async Use app send_task e celery task tasks Use celery registry tasks 13 5 4 Aliases Pending deprecation e celery task base Task gt app create_task_cls e celery task sets TaskSet gt app TaskSet e celery decorators celery task task gt app task e celery execute 320 Chapter 13 Internals Celery Documeniation Release 2 5 5 apply_async gt task apply_async apply gt task apply send_task gt app send_task delay_task gt no alternative e celery log get_default_logger gt app log get_default_logger setup_logger gt app log setup_logger get_task_logger gt app log get_task_logger setup_task_logger gt app log setup_task_logger setup_logging subsystem gt app log setup_logging subsystem redirect_stdouts_to_logger gt app log redirect_stdouts_to_logger e celery messagin
93. long to wait in seconds before the operation times out e propagate Re raise exception if the task failed e interval Time to wait in seconds before retrying to retrieve the result Note that this does not have any effect when using the AMQP result store backend as it does not use polling Raises celery exceptions TimeoutError if timeout is not None and the result does not arrive within timeout seconds If the remote call raised an exception then that exception will be re raised AsyncResult info When the task has been executed this contains the return value If the task raised an exception this will be the exception instance 268 Chapter 12 API Reference Celery Documeniation Release 2 5 5 AsyncResult ready Returns True if the task has been executed If the task is still running pending or is waiting for retry then False is returned AsyncResult result When the task has been executed this contains the return value If the task raised an exception this will be the exception instance AsyncResult revoke connection None connect_timeout None Send revoke signal to all workers Any worker receiving the task or having reserved the task must ignore it AsyncResult state The tasks current state Possible values includes PENDING The task is waiting for execution STARTED The task has been started RETRY The task is to be retried possibly because of failure FAILURE The task raised an ex
94. meaning the task result is not ready has not been executed EXCEPTION_STATES Set of states meaning the task returned an exception PROPAGATE_STATES Set of exception states that should propagate exceptions to the user ALL_STATES Set of all possible states 12 23 3 Misc celery states PRECEDENCE SUCCESS FAILURE None REVOKED STARTED RECEIVED RETRY PE State precedence None represents the precedence of an unknown state Lower index means higher precedence celery states precedence state Get the precedence index for state Lower index means higher precedence class celery states state State is a subclass of st r implementing comparison methods adhering to state precedence rules 12 23 celery states 287 Celery Documeniation Release 2 5 5 12 24 celery contrib abortable e Abortable tasks overview Usage example 12 24 1 Abortable tasks overview For long running Task s it can be desirable to support aborting during execution Of course these tasks should be built to support abortion specifically The AbortableTask serves as a base class for all Task objects that should support abortion by producers e Producers may invoke the abort method on AbortableAsyncResult instances to request abortion e Consumers workers should periodically check and honor the is_aborted method at controlled points in their task s run method Th
95. override PeriodicTask is_due or turn Periodic Task run_every into a property class MyPeriodic PeriodicTask def run self property def run_every self return get_interval_from_database 9 7 14 Does celery support task priorities Answer No In theory yes as AMQP supports priorities However RabbitMQ doesn t implement them yet The usual way to prioritize work in Celery is to route high priority tasks to different servers In the real world this may actually work better than per message priorities You can use this in combination with rate limiting to achieve a highly responsive system 158 Chapter 9 Frequently Asked Questions Celery Documeniation Release 2 5 5 9 7 15 Should I use retry or acks_late Answer Depends It s not necessarily one or the other you may want to use both Task retry is used to retry tasks notably for expected errors that is catchable with the try block The AMQP transaction is not used for these errors if the task raises an exception it is still acknowledged The acks_late setting would be used when you need the task to be executed again if the worker for some reason crashes mid execution It s important to note that the worker is not known to crash and if it does it is usually an unrecoverable error that requires human intervention bug in the worker or task code In an ideal world you could safely retry any task that has failed but this is rarely the case Imagin
96. port to the Tokyo Tyrant server close Close the tyrant connection and remove the cache delete key get key open Get pytyrant PyTyrant instance with the current server configuration The connection is then cached until you do an explicit close process_cleanup set key value tyrant_host None tyrant_port None 13 6 Internal Module Reference 365 Celery Documentation Release 2 5 5 13 6 30 celery execute trace e celery execute trace j celery execute trace This module defines how the task execution is traced errors are recorded handlers are applied and so on copyright 3 2009 2012 by Ask Solem license BSD see LICENSE for more details class celery execute trace TraceInfo state retval None exc_info None exc_info exc_type exc_value handle_error_state task eager False handle _ failure task store_errors True Handle exception handle_retry task store_errors True Handle retry exception retval state strtb tb celery execute trace build_tracer name task loader None hostname None store_errors True Info lt class cel ery execute trace Tracelnfo gt eager False propa gate False celery execute trace defines_custom_call task Returns true if the task or one of its bases defines __call__ excluding the one in BaseTask celery execute trace eager_trace_task task uuid args kwargs request None opts celery execute tr
97. raises an exception or successful if it returns Raises celery exceptions RetryTaskError To tell the worker that the task has been re sent for retry This always happens unless the throw keyword argument has been explicitly set to False and is considered normal operation Example gt gt gt task gt gt gt def tweet auth message twitter Twitter oauth auth try twitter post_status_update message except twitter FailWhale exc return tweet retry countdown 60 5 exc exc Although the task will never return above as retry raises an exception to notify the worker we use return in front of the retry to convey that the rest of the block will not be executed BaseTask routing_key None Overrides the apps default routing_key for this task BaseTask run args kwargs The body of the task executed by workers BaseTask send_error_emails False If enabled an email will be sent to ADMINS whenever a task of this type fails 254 Chapter 12 API Reference Celery Documeniation Release 2 5 5 BaseTask serializer pickle The name of a serializer that are registered with kombu serialization registry Default is pickle BaseTask soft_time_limit None Soft time limit Defaults to the CELERY_TASK_SOFT_TIME_LIMIT setting BaseTask store_errors_even_if_ignored False When enabled errors will be stored even if the task is otherwise configured to ignore results classmethod
98. reserved for the workers Consumer since it is required to always be started last There can only be one object marked with Isat in every namespace name None The name of the component or the namespace and the name of the component separated by dot namespace None can be used to specify the namespace if the name does not include it obj None Optional obj created by the create method This is used by StartStopComponents to keep the original service object requires List of component names this component depends on Note that the dependencies must be in the same namespace class celery abstract ComponentType Metaclass for components class celery abstract Namespace name None app None logger None A namespace containing components Every component must belong to a namespace When component classes are created they are added to the mapping of unclaimed components The components will be claimed when the namespace they belong to is created Parameters e name Set the name of this namespace e app Set the Celery app for this namespace apply parent kwargs Apply the components in this namespace to an object This will apply the __init__ and include methods of each components with the object as argument For StartStopComponents the services created will also be added the the objects components attribute bind_component name parent kwargs Bind component to parent object and this namespace
99. resulted in failure metadata result contains the exception occurred and traceback contains the backtrace of the stack at the point when the exception was raised propagates Yes 2 2 Tasks 27 Celery Documeniation Release 2 5 5 RETRY Task is being retried metadata result contains the exception that caused the retry and traceback contains the backtrace of the stack at the point when the exceptions was raised propagates No REVOKED Task has been revoked propagates Yes Custom states You can easily define your own states all you need is a unique name The name of the state is usually an uppercase string As an example you could have a look at abortable tasks which defines its own custom ABORTED state Use Task update_state to update a task s state task def upload files filenames for i in 1 filenames upload_files update_state state PROGRESS meta current i total filenames Here we created the state PROGRESS which tells any application aware of this state that the task is currently in progress and also where it is in the process by having current and total counts as part of the state metadata This can then be used to create e g progress bars Creating pickleable exceptions A little known Python fact is that exceptions must behave a certain way to support being pickled Tasks that raise exceptions that are not pickleable will not work properly when Pickle is used as the
100. returns Deprecated Use with app default_connection connection instead mail_admins subject body fail_silently False Send an email to the admins in the ADMINS setting prepare_config c Prepare configuration before it is merged with the defaults either default_key values Fallback to the value of a configuration key if none of the values are true merge r Like dict a b except it will keep values from a if the value in b is None 12 1 2 Functions celery app app_or_ default app None Returns the app provided or the default app if none The environment variable CELERY_TRACE_APP is used to trace app leaks When enabled an exception is raised if there is no active app 12 2 celery app task e celery app task j 12 2 1 celery app task Tasks Implementation copyright 3 2009 2012 by Ask Solem license BSD see LICENSE for more details class celery app task TaskType Meta class for tasks Automatically registers the task in the task registry except if the abstract attribute is set If no name attribute is provided then no name is automatically set to the name of the module it was defined in and the class name class celery app task BaseTask Task base class When called tasks apply the run method This method must be defined by all tasks that is unless the ___call___ method is overridden 248 Chapter 12 API Reference Celery Documeniation Release 2 5 5 clas
101. separate module and symbol celery concurrency processes TaskPool If aliases is provided a dict containing short name long name mappings the name is looked up in the aliases first Examples gt gt gt get_cls_by_name celery concurrency processes TaskPool class celery concurrency pro s T gt gt gt gt get_cls_by_name default default celery concurrency processes TaskPool T Pool lt class celery concurrency processes Tas Does not try to look up non string names gt gt gt from celery concurrency processes import TaskPool gt gt gt get_cls_by_name TaskPool is TaskPool True 13 6 Internal Module Reference 377 Celery Documeniation Release 2 5 5 celery utils get_full_cls_name obj celery utils get_symbol_by name name aliases imp None package None sep kwargs Get class by name The name should be the full dot separated path to the class modulename ClassName Example celery concurrency processes TaskPool class name or using to separate module and symbol celery concurrency processes TaskPool If aliases is provided a dict containing short name long name mappings the name is looked up in the aliases first Examples gt gt gt get_cls_by_name celery concurrency processes TaskPool lt class celery concurrency processes TaskPool gt gt gt gt get_cls_by_name default default celery concurrency proce
102. serializing task arguments so be sure to flush your task queue before you upgrade IMPORTANT TaskSet run now returns a celery result TaskSetResult instance which lets you inspect the status and return values of a taskset as it was a single entity IMPORTANT Celery now depends on carrot gt 0 4 1 The celery daemon now sends task errors to the registered admin emails To turn off this feature set SEND_CELERY_TASK_ERROR_EMAILS to False in your settings py Thanks to Gr goire Cachet You can now run the celery daemon by using manage py S python manage py celeryd Thanks to Gr goire Cachet Added support for message priorities topic exchanges custom routing keys for tasks This means we have introduced celery task apply_async a new way of executing tasks You can use celery task delay and celery Task delay like usual but if you want greater control over the message sent you want celery task apply_async and celery Task apply_async This also means the AMQP configuration has changed Some settings has been renamed while others are new ERY_AMOP_ EXCHANGE ERY_AMOP_PUBLISHER_ROUTING_KEY ERY_AMOP_CONSUMER_ROUTING_KEY ERY_AMQP_CONSUMER_QUEUE ERY_AMOP_EXCHANGE_TYPE GOTA See the entry Can I send some tasks to only some servers in the FAQ for more information Task errors are now logged using log level ERROR instead of INF
103. t crash the worker processes e The remote control command replies was not working with RabbitMQ 1 8 0 s stricter equivalence checks If you ve already hit this problem you may have to delete the declaration camgqadm exchange delete celerycrg or python manage py camgqadm exchange delete celerycrg e A bug sneaked in the ETA scheduler that made it only able to execute one task per second The scheduler sleeps between iterations so it doesn t consume too much CPU It keeps a list of the scheduled items sorted by time at each iteration it sleeps for the remaining time of the item with the nearest deadline If there are no eta tasks it will sleep for a minimum amount of time one second by default 11 33 2 0 1 209 Celery Documentation Release 2 5 5 A bug sneaked in here making it sleep for one second for every task that was scheduled This has been fixed so now it should move tasks like hot knife through butter In addition a new setting has been added to control the minimum sleep interval CELERYD_ETA_SCHEDULER_PRECISION A good value for this would be a float between 0 and 1 depending on the needed precision A value of 0 8 means that when the ETA of a task is met it will take at most 0 8 seconds for the task to be moved to the ready queue Pool Supervisor did not release the semaphore This would lead to a deadlock if all workers terminated prematurely Added Python
104. task This means that the following will have magic keyword arguments enabled old style from celery decorators import task task def add x y xkwargs print In task s kwargs task_id return x y 11 25 2 2 0 189 Celery Documentation Release 2 5 5 And this will not use magic keyword arguments new style from celery task import task task def add x y print In task s add request id return x y In addition tasks can choose not to accept magic keyword arguments by setting the task accept_magic_kwargs attribute Deprecation Using the decorators in celery decorators emits a PendingDeprecationWarning with a helpful message urging you to change your code in version 2 4 this will be replaced with a DeprecationWarning and in version 3 0 the celery decorators module will be removed and no longer exist Similarly the task accept_magic_kwargs attribute will no longer have any effect starting from version 3 0 e The magic keyword arguments are now available as task request This is called the context Using thread local storage the context contains state that is related to the current request It is mutable and you can add custom attributes that will only be seen by the current task request The following context attributes are always available Magic Keyword Argument Replace with kwargs task_id self request id kwargs delivery_info self request delive
105. terminal celeryd loglevel INFO In production you will probably want to run the worker in the background as a daemon To do this you need to use the tools provided by your platform or something like supervisord see Running celeryd as a daemon for more information For a complete listing of the command line options available do celeryd help 1 3 5 Executing the task Whenever we want to execute our task we use the delay method of the task class This is a handy shortcut to the apply_async method which gives greater control of the task execution see Executing Tasks gt gt gt from tasks import add gt gt gt add delay 4 4 lt AsyncResult 889143a6 39a2 4e52 837b d80d33efb22d gt At this point the task has been sent to the message broker The message broker will hold on to the task until a worker server has consumed and executed it 14 Chapter 1 Getting Started Celery Documeniation Release 2 5 5 Right now we have to check the worker log files to know what happened with the task Applying a task returns an AsyncResult if you have configured a result store the AsyncResult enables you to check the state of the task wait for the task to finish get its return value or exception traceback if the task failed and more Keeping Results If you want to keep track of the tasks state Celery needs to store or send the states somewhere There are several built in backends to choose from SQLAIc
106. test database and you won t be able to get the return value or check the status of your tasks There are two ways to get around this You can either take advantage of CELERY_ALWAYS_EAGER True to skip the daemon or you can avoid testing anything that needs to check the status or result of a task 4 2 2 Using a custom test runner to test with celery If you re going the CELERY_ALWAYS_EAGER route which is probably better than just never testing some parts of your app a custom Django test runner does the trick Celery provides a simple test runner but it s easy enough to roll your own if you have other things that need to be done http docs djangoproject com en dev topics testing defining a test runner For this example we ll use the djcelery contrib test_runner to test the add task from the Tasks examples in the Celery documentation To enable the test runner set the following settings 4 2 Unit Testing 111 Celery Documentation Release 2 5 5 H EST_RUNNER djcelery contrib test_runner CeleryTestSuiteRunner Then we can put the tests in a tests py somewhere from django test import TestCase from myapp tasks import add class AddTestCase TestCase def testNoError ye Test that the add task runs with no errors and returns the correct result result add delay 8 8 assertEquals result get 16 assertTrue result successful
107. than a few workers can lead to messages being executed multiple times 1 2 4 Using the Django Database Installation Configuration The database transport uses the Django DATABASE_ settings for database configuration values 1 Set your broker transport BROKER_URL django 2 Add kombu transport django to INSTALLED_APPS INSTALLED_APPS kombu transport django 3 Sync your database schema S python manage py syncdb Limitations The Django database transport does not currently support e Remote control commands celeryev broadcast e Events including the Django Admin monitor e Using more than a few workers can lead to messages being executed multiple times 1 2 5 Using MongoDB Installation For the MongoDB support you have to install additional dependencies You can install both Celery and these depen dencies in one go using either the celery with mongodb or the django celery with mongodb bundles 10 Chapter 1 Getting Started Celery Documeniation Release 2 5 5 pip install U celery with mongodb Configuration Configuration is easy set the transport and configure the location of your MongoDB database BROKER_URL mongodb localhost 27017 database_name Where the URL is in the format of mongodb userid password hostname port database_name The host name will default to Localhost and the port to 27017 and so they are optional userid and password are also optiona
108. that RabbitMQ does not support priorities 12 2 celery app task 253 Celery Documentation Release 2 5 5 BaseTask queue None Destination queue The queue needs to exist in CELERY_QUEUES The routing_key exchange and ex change_type attributes will be ignored if this is set BaseTask rate_limit None Rate limit for this task type Examples None no rate limit 00 s hundred tasks a second 100 m hundred tasks a minute 100 h hundred tasks an hour BaseTask request lt Context gt Request context set when task is applied classmethod BaseTask retry args None kwargs None exc None throw True eta None countdown None max_retries None options Retry the task Parameters e args Positional arguments to retry with e kwargs Keyword arguments to retry with e exc Optional exception to raise instead of MaxRetriesExceededError when the max restart limit has been exceeded e countdown Time in seconds to delay the retry for e eta Explicit time and date to run the retry at must be a dat et ime instance e max_retries If set overrides the default retry limit e options Any extra options to pass on to meth apply_async e throw If this is False do not raise the RetryTaskError exception that tells the worker to mark the task as being retried Note that this means the task will be marked as failed if the task
109. the I include option This is an experimental feature intended for use in development only using auto reload in production is discouraged as the behavior of reloading a module in Python is undefined and may cause hard to diagnose bugs and crashes Celery uses the same approach as the auto reloader found in e g the Django runserver command 44 Chapter 2 User Guide Celery Documeniation Release 2 5 5 When auto reload is enabled the worker starts an additional thread that watches for changes in the file system New modules are imported and already imported modules are reloaded whenever a change is detected and if the processes pool is used the child processes will finish the work they are doing and exit so that they can be replaced by fresh processes effectively reloading the code File system notification backends are pluggable and it comes with three implementations e inotify Linux Used if the pyinotify library is installed If you are running on Linux this is the recommended implementation to install the pyinotify library you have to run the following command pip install pyinotify e kqueue OS X BSD e stat The fallback implementation simply polls the files using st at and is very expensive You can force an implementation by setting the CELERYD_FSNOTIFY environment variable env CELERYD_FSNOTIFY stat celeryd l info autoreload 2 4 9 Remote conirol New in version 2
110. the event of connection loss or failure Default is taken from the CELERY_TASK_PUBLISH_RETRY setting Note you need to handle the publisher connection manually for this to work retry_policy Override the retry policy used See the CELERY_TASK_PUBLISH_RETRY setting e routing_key The routing key used to route the task to a worker server Defaults to the rout ing_key attribute exchange The named exchange to send the task to Defaults to the exchange attribute exchange_type The exchange type to initialize the exchange if not already declared Defaults to the exchange_type attribute e immediate Request immediate delivery Will raise an exception if the task cannot be routed to a worker immediately Do not confuse this parameter with the countdown and eta settings as they are unrelated Defaults to the immediate attribute e mandatory Mandatory routing Raises an exception if there s no running workers able to take on this task Defaults to the mandatory attribute priority The task priority a number between 0 and 9 Defaults to the priority attribute serializer A string identifying the default serialization method to use Can be pickle json yaml msgpack or any custom serialization method that has been registered with kombu serialization registry Defaults to the serializer attribute e compression A string identifying the compression method to use Can be one of zl
111. til til til trace 9 29 29 lery signals 29 lery states lery tas lery task base lery task chords lery task control lery task http lery task sets k 2 s o s 22 s e ls compat ls dispatch ls dispatch saferef ls dispatch signal ls encoding ls functional ls mail ls patch s serialization 395 Celery Documentation Release 2 5 5 celery utils term celery utils threads celery utils timer2 celery utils timeutils celery worker celery worker autoreload celery worker autoscale celery worker buckets celery worker consumer celery worker heartbeat celery worker job celery worker mediator celery worker state celery worker strategy 396 Python Module Index
112. times in a given period of time is the task allowed to run If this is None no rate limit is in effect If it is an integer it is interpreted as tasks per second The rate limits can be specified in seconds minutes or hours by appending s m or h to the value Example 00 m hundred tasks a minute Default is the CELERY_DEFAULT_RATE_LIMIT setting which if not specified means rate limiting for tasks is disabled by default Task time_limit The hard time limit for this task If not set then the workers default will be used Task soft_time_limit The soft time limit for this task If not set then the workers default will be used Task ignore_result Don t store task state Note that this means you can t use AsyncResult to check if the task is ready or get its return value Task store_errors_even_if_ignored If True errors will be stored even if the task is configured to ignore results Task send_error_emails Send an email whenever a task of this type fails Defaults to the CELERY_SEND_TASK_ERROR_EMAILS setting See Error E Mails for more information Task error_whitelist If the sending of error emails is enabled for this task then this is a white list of exceptions to actually send emails about Task serializer A string identifying the default serialization method to use Defaults to the CELERY_TASK_SERIALIZER setting Can be pickle json yaml o
113. version trove classifiers 2 4 2 5 2 6 and 2 7 Tests now passing on Python 2 7 Task __reduce__ Tasks created using the task decorator can now be pickled setup py nose added to tests_require Pickle should now work with SQLAIchemy 0 5 x New homepage design by Jan Henrik Helmers http celeryproject org New Sphinx theme by Armin Ronacher http docs celeryproject org Fixed pending _xref errors shown in the HTML rendering of the documentation Apparently this was caused by new changes in Sphinx 1 0b2 Router classes in CELERY_ROUTES are now imported lazily Importing a router class in a module that also loads the Celery environment would cause a circular dependency This is solved by importing it when needed after the environment is set up ELERY_ROUTES was broken if set to a single dict This example in the docs should now work again CELERY_ROUTES feed tasks import_feed feeds CREATE_MISSING_QUEUES was not honored by apply_async New remote control command stats Dumps information about the worker like pool process ids and total number of tasks executed by type Example reply worker local total tasks sleeptask 6 pool timeouts None None processes 60376 60377 max concurrency 2 max tasks per child None put guarded by semaphore True e New remote control command du
114. will be retried in the case of connection loss or other connection errors See also CELERY_TASK_PUBLISH_RETRY_POLICY Disabled by default 98 Chapter 3 Configuration and defaults Celery Documeniation Release 2 5 5 CELERY_TASK_PUBLISH_RETRY_POLICY New in version 2 2 Defines the default policy when retrying publishing a task message in the case of connection loss or other connection errors This is a mapping that must contain the following keys e max_retries Maximum number of retries before giving up in this case the exception that caused the retry to fail will be raised A value of 0 or None means it will retry forever The default is to retry 3 times e interval_start Defines the number of seconds float or integer to wait between retries Default is 0 which means the first retry will be instantaneous e interval_step On each consecutive retry this number will be added to the retry delay float or integer Default is 0 2 e interval_max Maximum number of seconds float or integer to wait between retries Default is 0 2 With the default policy of max_retries 3 interval_start 0 interval_step 0 2 i3nterval_max 0 2 the maximum time spent retrying will be 0 4 seconds It is set relatively short by default because a connection failure could lead to a retry pile effect if the broker connection is down e g many web server processes waiting to retry blocking other incomin
115. with a new one Default is no limit CELERYD_TASK_TIME_LIMIT Task hard time limit in seconds The worker processing the task will be killed and replaced with a new one when this is exceeded CELERYD_TASK_SOFT_TIME_LIMIT Task soft time limit in seconds The SoftTimeLimitExceeded exception will be raised when this is exceeded The task can catch this to e g clean up before the hard time limit comes Example from celery task import task from celery exceptions import SoftTimeLimitExceeded task def mytask try return do_work except SoftTimeLimitExceeded cleanup_in_a_hurry CELERY_STORE_ERRORS_EVEN_IF_IGNORED If set the worker stores all task errors in the result store even if Task ignore_result is on 100 Chapter 3 Configuration and defaults Celery Documeniation Release 2 5 5 CELERYD_STATE_DB Name of the file used to stores persistent worker state like revoked tasks Can be a relative or absolute path but be aware that the suffix db may be appended to the file name depending on Python version Can also be set via the st atedb argument to celeryd Not enabled by default CELERYD_ETA_SCHEDULER_PRECISION Set the maximum time in seconds that the ETA scheduler can sleep between rechecking the schedule Default is 1 second Setting this value to 1 second means the schedulers precision will be 1 second If you need near millisecond precision you can set this to 0 1 3 2 17 Err
116. without preload options parse_options prog_name arguments Parse the available options parse_preload_options args preload_options lt Option at 0x5c213f8 app gt lt Option at 0x5acf950 b broker gt lt Option at 0x5acf998 loade List of options to parse before parsing other options prepare_preload_options options Optional handler to do additional processing of preload options Configuration must not have been initialized until after this is called process_cmdline_config argv 12 32 celery bin base 299 Celery Documeniation Release 2 5 5 run args options This is the body of the command called by handle_argv setup_app_from_commandline argv supports_args True If false the parser will raise an exception if positional args are provided usage Returns the command line usage string for this app version 2 5 5 Application version celery bin base daemon_options default_pidfile None default_logfile None 12 33 celery bin celeryd celeryd c concurrency Number of child processes processing the queue The default is the number of CPUs available on your system f logfile Path to log file If no logfile is specified stderr is used 1 loglevel Logging level choose between DEBUG INFO WARNING ERROR CRITICAL or FATAL n hostname Set custom hostname B beat Also run the celerybeat periodic task scheduler Please note that there must
117. work in a way that allows outsiders to test discuss and contribute to your efforts 6 1 4 When you disagree consult others Disagreements both political and technical happen all the time and the Celery community is no exception It is important that we resolve disagreements and differing views constructively and with the help of the community and community process If you really want to go a different way then we encourage you to make a derivative distribution or alternate set of packages that still build on the work we ve done to utilize as common of a core as possible 6 1 5 When you are unsure ask for help Nobody knows everything and nobody is expected to be perfect Asking questions avoids many problems down the road and so questions are encouraged Those who are asked questions should be responsive and helpful However when asking a question care must be taken to do so in an appropriate forum 6 1 Community Code of Conduct 121 Celery Documeniation Release 2 5 5 6 1 6 Step down considerately Developers on every project come and go and Celery is no different When you leave or disengage from the project in whole or in part we ask that you do so in a way that minimizes disruption to the project This means you should tell people you are leaving and take the proper steps to ensure that others can pick up where you leave off 6 2 Reporting a Bug Bugs can always be described to the Mailing list but the best way to
118. you paver readme Now commit the changes git commit a m Bumps version to X Y 2 and make a new version tag git tag vxX Y Z git push tags 6 10 2 Releasing Commands to make a new public stable release paver releaseok checks pep8 autodoc index and runs tests paver removepyc Remove pyc files git clean xdn Check that there s no left over files in the repository python2 5 setup py sdist upload Upload package to PyPI paver upload_pypi_docs paver ghdocs Build and upload documentation to Github T Ur r Or D wm If this is a new release series then you also need to do the following 132 Chapter 6 Contributing Celery Documeniation Release 2 5 5 e Go to the Read The Docs management interface at http readthedocs org projects celery fromdocs celery e Enter Edit project Change default branch to the branch of this series e g 2 4 for series 2 4 e Also add the previous version under the versions tab 6 10 3 Updating bundles First you need to make sure the bundle entrypoints have been installed but either running develop or install python setup py develop Then make sure that you have your PyPI credentials stored in pypirc and execute the command python setup py upload_bundles If you broke something and need to update new versions of the bundles then you can use up load_bundles_fix 6 10 Release Procedure 133 Celery Documeniation Releas
119. 0 Workers have the ability to be remote controlled using a high priority broadcast message queue The commands can be directed to all or a specific list of workers Commands can also have replies The client can then wait for and collect those replies Since there s no central authority to know how many workers are available in the cluster there is also no way to estimate how many workers may send a reply so the client has a configurable timeout the deadline in seconds for replies to arrive in This timeout defaults to one second If the worker doesn t reply within the deadline it doesn t necessarily mean the worker didn t reply or worse is dead but may simply be caused by network latency or the worker being slow at processing commands so adjust the timeout accordingly In addition to timeouts the client can specify the maximum number of replies to wait for If a destination is specified this limit is set to the number of destination hosts See also The celeryctl program is used to execute remote control commands from the command line It supports all of the commands listed below See celeryctl Management Utility for more information The broadcast function This is the client function used to send commands to the workers Some remote control commands also have higher level interfaces using broadcast in the background like rate_limit andping Sending the rate_limit command and keyword arguments gt gt gt
120. 0 Django Celery Quickstart or how I learned to stop using cron and love celery Using Python magic to improve the deferred API How Celery Carrot and your messaging stack work Large Problems in Django Mostly Solved Delayed Execution Introduction to Celery RabbitMQ Celery and Django Message Queues Django and Celery Quick Start Background task processing and deferred execution in Django Build a processing queue in less than a day using RabbitMQ and Celery How to get celeryd to work on FreeBSD Web based 3D animation software Queued Storage Backend for Django RabbitMQ with Python and Ruby 136 Chapter 7 Community Resources Celery Documeniation Release 2 5 5 7 1 Resources 7 1 1 Who s using Celery http wiki github com celery celery using 7 1 2 Wiki http wiki github com celery celery 7 1 3 Celery questions on Stack Overflow http stackoverflow com search q celery amp tab newest 7 1 4 Mailing list Archive celery users http blog gmane org gmane comp python amap celery user 7 1 5 IRC Logs http botland oebfare com logger celery 7 2 News 7 2 1 Celery Mini Tutorial Catalan http trespams com 2010 1 1 28 celery mini tutorial 7 2 2 Building a Django App Server with Chef http ericholscher com blog 2010 nov 1 1 building django app server chef part 4 7 2 3 Introducci a Celery Catalan http trespams com 2010 11 13 introduccio celery 7 2 4 Django and Celery
121. 08 05 12 00 PM BST tested cPython 2 5 2 6 2 7 PyPy 1 5 Jython 2 5 2 11 16 1 Important Notes e Now requires Kombu 1 2 1 e Results are now disabled by default The AMQP backend was not a good default because often the users were not consuming the results resulting in thousands of queues While the queues can be configured to expire if left unused it was not possible to enable this by default because this was only available in recent RabbitMQ versions 2 1 1 With this change enabling a result backend will be a conscious choice which will hopefully lead the user to read the documentation and be aware of any common pitfalls with the particular backend 180 Chapter 11 Change history Celery Documeniation Release 2 5 5 The default backend is now a dummy backend celery backends base DisabledBackend Saving state is simply an noop operation and AsyncResult wait result state etc will raise a NotImplementedError telling the user to configure the result backend For help choosing a backend please see Result Backends If you depend on the previous default which was the AMQP backend then you have to set this explicitly before upgrading CELERY_RESULT_BACKEND amqp Note For django celery users the default backend is still database and results are not disabled by default e The Debian init scripts have been deprecated in favor of the generic init d init scripts In addition gener
122. 08e None h10 By ETA 842b 46e4 96576157 e6ca 48d1 b844 8b Any date 9998 T 7632460b40b3 Fda O ce47e922 SUCCESS statuses_twitter_update e97c687d130871614a6da1768d8t3d8e None h9 his month c76c 45aa 96576157 e6ca 4841 b8d4 8b This year 8885 c2d853e05dbb By worker All O 2ebb8254 SUCCESS statuses_twitter_update e97 687d130871614a6d8176808T3d8e None h10 h10 6891 4b6c 96576157 e6ca 4841 b8d4 8b abe7 PTE OPO he Starting the monitor The Celery section will already be present in your admin interface but you won t see any data appearing until you start the snapshot camera The camera takes snapshots of the events your workers sends at regular intervals storing them in your database See Snapshots To start the camera run python manage py celerycam If you haven t already enabled the sending of events you need to do so python manage py celeryctl inspect enable_events Tip You can enable events when the worker starts using the E argument to celeryd Now that the camera has been started and events have been enabled you should be able to see your workers and the tasks in the admin interface it may take some time for workers to show up The admin interface shows tasks worker nodes and even lets you perform some actions like revoking and rate limiting tasks or shutting down worker nodes Shutter frequency By default the camera takes a snapshot every second if this is
123. 1 18 2 2 7 release date 2011 06 13 16 00 P M BST e New signals after_setup_logger and after_setup_task_logger These signals can be used to augment logging configuration after Celery has set up logging 11 17 2 2 8 183 Celery Documeniation Release 2 5 5 e Redis result backend now works with Redis 2 4 4 e celeryd_multi The gid option now works correctly e celeryd Retry wrongfully used the repr of the traceback instead of the string representation e App config_from_object Now loads module not attribute of module e Fixed issue where logging of objects would give lt Unrepresentable gt 11 19 2 2 6 release date 2011 04 15 16 00 P M CEST 11 19 1 Important Notes e Now depends on Kombu 1 1 2 e Dependency lists now explicitly specifies that we don t want python dateutil 2 x as this version only supports py3k If you have installed dateutil 2 0 by accident you should downgrade to the 1 5 0 version pip install U python dateutil 1 5 0 or by easy_install easy_install U python dateutil 1 5 0 11 19 2 Fixes The new Wat chedFileHandler broke Python 2 5 support Issue 367 Task Don t use app main if the task name is set explicitly Sending emails did not work on Python 2 5 due to a bug in the version detection code Issue 378 Beat Adds method ScheduleEntry _default_now This method can be overridden to change the default value of Last_run_at An error occurrin
124. 1 37 1 0 4 221 Celery Documentation Release 2 5 5 Late ack means the task messages will be acknowledged after the task has been executed not just before which is the default behavior Note This means the tasks may be executed twice if the worker crashes in mid execution Not acceptable for most applications but desirable for others e Added crontab like scheduling to periodic tasks Like a cron job you can specify units of time of when you would like the task to execute While not a full implementation of cron s features it should provide a fair degree of common scheduling needs You can specify a minute 0 59 an hour 0 23 and or a day of the week 0 6 where 0 is Sunday or by names sun mon tue wed thu fri sat Examples from celery schedules import crontab from celery decorators import periodic_task periodic_task run_every crontab hour 7 minute 30 def every _morning print Runs every morning at 7 30a m periodic_task run_every crontab hour 7 minute 30 day_of_week mon def every monday _morning print Run every monday morning at 7 30a m periodic_task run_every crontab minutes 30 def every hour print Runs every hour on the clock e g 1 30 2 30 3 30 etc Note This a late addition While we have unittests due to the nature of this feature we haven t been able to completely test this in practice so consider this experimental TaskPool apply_asy
125. 1 433e 4cae 8882 9FFFFc2c09d6 tasks sleeptask casper local 10 02 30 SUCCESS ce at Local casper oca 10 02 21 SUCCESS 2599b117 3c10 45a3 8544 2663b284c96F tasks sleeptesk casper local 7a 7fccl 7a13 4878 82a6 738673e4c3d9 tasks sleeptask casper local 10 02 18 RECEIVED 75486d0d aae4 4129 bc55 febaGa2abe3 tasks sleeptask casper local 10 02 18 RECEIVED e47e2069 a2bf 4af3 a93d c3ef96Ffdl2c tasks sleeptask casper local 10 02 18 RECEIVED 3a7a6759 7fa8 48ec 9 f89 b222acd3b49F tasks sleeptask 1 feclb6 6996 41 f9 a337 989adec5183d tasks sleeptask casper local casper local 10 02 18 RECEIVED 10 02 18 RECEIVED fda219d3 c24b 492c b948 9F 9b1945e8d tasks sleeptask casper local 10 02 18 RECEIVED 627428a6 a9ed 4c3b ad64 a869b582e068 tasks sleeptask casper local 10 02 18 RECEIVED 872052d0 71b6 4287 a24d d6 fda e8ebc tasks sleeptask casper local 10 02 18 RECEIVED c8d a21e aac2 4f3a 90d6 fee3b94caaca tasks sleeptask casper local 10 02 18 RECEIVED 1c9d67d8 b8f 4fd 8d30 e72694526df3 tasks sleeptask casper local 10 02 18 RECEIVED 6b179f86 4be5 4b0e a81b e25525c3a02a tasks sleeptask casper local 10 02 18 RECEIVED c 2ffdid 36a8 4 c4 a5al 9aedfcbaSeeb tasks sleeptask casper local 10 02 18 RECEIVED 3795b272 b5e4 429e 84e3 583d8e02261b tasks sleeptask casper local 10 02 18 641 ee9b 0ea7 4fF8 b40d 4ca023038fel tasks sleeptask casper local 10 02 18 6d1 4daf2 5025 48ea b445 ca4b9fcc9369 tasks sleeptask casper local 10 02 18 SUCCESS Selected runt
126. 12 by Ask Solem license BSD see LICENSE for more details class celery utils term colored s kwargs Terminal colored text Example gt gt gt c colored enabled gt gt gt print c red the quick c blue brown c bold fox c magenta c underline jumps over c yellow the lazy c green dog black s blink s blue s bold s bright s cyan s embed green s iblue s icyan s igreen s imagenta s ired s iwhite s iyellow s magenta s no_color 380 Chapter 13 Internals Celery Documeniation Release 2 5 5 node s op red s reset s reverse s underline s white s yellow s celery utils term fg s 13 6 47 celery utils timeutils e celery utils timeutils j celery utils timeutils This module contains various utilities relating to dates and times copyright 3 2009 2012 by Ask Solem license BSD see LICENSE for more details exception celery utils timeutils UnknownTimezone No specification exists for the timezone specified Consider installing the pytz library to get access to more timezones celery utils timeutils delta_resolution dt delta Round a datetime to the resolution of a timedelta If the timedelta is in days the datetime will be rounded to the nearest days if the timedelta is in hours the datetime will be rounded to the nearest hour and so on until seconds which will just ret
127. 2 16 1 celery utils mail How task error emails are formatted and sent copyright 3 2009 2012 by Ask Solem license BSD see LICENSE for more details class celery utils mail ErrorMail task kwargs Defines how and when task error e mails should be sent Parameters task The task instance that raised the error subject and body are format strings which are passed a context containing the following keys name Name of the task UUID of the task eXC String representation of the exception eargs Positional arguments ekwargs Keyword arguments etraceback String representation of the traceback ehostname Worker hostname EMAIL SIGNATURE_SEP body nTask name s with id id s raised exception n exc r n n nTask was called with args args s kwargs Format string used to generate error email content error_whitelist None format_body context format_subJect context send context exc fail_silently True should_send context exc Returns true or false depending on if a task error mail should be sent for this type of error subject celery hostname s Error Task name s id s exc s n Format string used to generate error email subjects class celery utils mail Mailer host localhost port 0 user None password None timeout 2 use_ssl False use_tls False send message 12 16 celery utils mail 281 Celery Docu mentation Release 2 5 5 class ce
128. 2 7 HTTP Callback Tasks Webhooks 57 Celery Documentation Release 2 5 5 result x y response status success retval result return HttpResponse serialize response mimetype application json 2 7 3 Ruby on Rails webhook example or in Ruby on Rails def multiply x params x to_i y params y to_i status status gt success retval gt x x y render json gt status end You can easily port this scheme to any language framework new examples and libraries are very welcome 2 7 4 Executing webhook tasks To execute the task you use the URL class gt gt gt from celery task http import URL gt gt gt res URL http example com multiply get_async x 10 y 10 URL is a shortcut to the HttpDispatchTask You can subclass this to extend the functionality gt gt gt from celery task http import HttpDispatchTask gt gt gt res HttpDispatchTask delay url http example com multiply method GET x 10 y 10 gt gt gt res get 100 The output of celeryd or the log file if enabled should show the task being executed INFO MainProcess Task celery task http HttpDispatchTask f2cc8efc 2al4 40cd 85ad flc77c94beeb processed 100 Since applying tasks can be done via HTTP using the djcelery views apply view executing tasks from other languages is easy For an example service exposing tasks via HTTP you should have a look at examples celery_http_gat
129. 2 8 Cache backend settings Note The cache backend supports the pylibmc and python memcached libraries The latter is used only if pylibmc is not installed CELERY_CACHE_BACKEND Using a single memcached server CELERY_CACHE_BACKEND memcached 127 0 0 1 11211 Using multiple memcached servers CELERY_RESULT_BACKEND cache CELERY_CACHE_BACKEND memcached 172 19 26 240 11211 172 19 26 242 11211 H The dummy backend stores the cache in memory only CELERY_CACHE_BACKEND dummy CELERY_CACHE_BACKEND_OPTIONS You can set pylibmc options using the CELERY_CACHE_BACKEND_OPTIONS setting CELERY_CACHE_BACKEND_OPTIONS binary True behaviors tcp_nodelay True 3 2 Configuration Directives 91 Celery Documentation Release 2 5 5 3 2 9 Tokyo Tyrant backend settings Note The Tokyo Tyrant backend requires the pyt yrant library http pypi python org pypi pytyrant This backend requires the following configuration directives to be set TT_HOST Host name of the Tokyo Tyrant server TT_PORT The port the Tokyo Tyrant server is listening to Example configuration CELERY_RESULT_BACKEND tyrant TT_HOST localhost TT_PORT 1978 3 2 10 Redis backend settings Note The Redis backend requires the redis library http pypi python
130. 324 Chapter 13 Internals Celery Documeniation Release 2 5 5 import_module module load_modules Will load the component modules this namespace depends on modules Subclasses can override this to return a list of modules to import before components are claimed name None class celery abstract StartStopComponent parent kwargs include parent start stop terminable False terminate 13 6 2 celery worker e celery worker j celery worker WorkController can be used to instantiate in process workers The worker consists of several components all managed by boot steps mod celery abstract copyright 3 2009 2012 by Ask Solem license BSD see LICENSE for more details class celery worker Beat w embed_clockservice False kwargs Component used to embed a celerybeat process This will only be enabled if the embed_clockservice argument is set create w name beat namespace worker class celery worker Namespace name None app None logger None This is the boot step namespace of the WorkController It loads modules from CELERYD_BOOT_STEPS and its own set of built in boot step modules builtin_boot_steps celery worker autoscale celery worker autoreload celery worker consumer celery work modules name worker 13 6 Internal Module Reference 325 Celery Documentation Release 2 5 5 class celery wo
131. 6 3 What features are not supported when not using an AMQP broker This is an incomplete list of features not available when using the virtual transports e Remote control commands supported only by Redis e Monitoring with events may not work in all virtual transports The header and fanout exchange types fanout is supported by Redis 9 7 Tasks 9 7 1 How can I reuse the same connection when applying tasks Answer See the BROKER_POOL_LIMIT setting The connection pool is enabled by default since version 2 5 9 7 2 Sudo in a subprocess returns None There is a sudo configuration option that makes it illegal for process without a tty to run sudo Defaults requiretty If you have this configuration in your etc sudoers file then tasks will not be able to call sudo when celeryd is running as a daemon If you want to enable that then you need to remove the line from sudoers See http timelordz com wiki Apache_Sudo_Commands 9 7 3 Why do workers delete tasks from the queue if they are unable to process them Answer The worker discards unknown tasks messages with encoding errors and messages that doesn t contain the proper fields as per the task message protocol If it did not ack delete them they would be redelivered again and again causing a loop There has been talk about moving these messages to a dead letter queue but that has not yet been implemented 9 7 4 Can I execute a task by name Answer Yes Use
132. 60 parse 15 0 15 30 45 gt gt gt hours crontab_parser 24 parse 4 O 4 8 12 1 20 gt gt gt day_of_week crontab_parser 7 parse 0 1 2 3 4 5 6 exception ParseException Raised by crontab_parser when the input can t be parsed crontab_parser parse spec celery schedules maybe_schedule s relative False class celery schedules schedule run_every None relative False nowfun None human_seconds is due last_run_at Returns tuple of two items is_due next_time_to_run where next time to run is in seconds e g True 20 means the task should be run now and the next time to run is in 20 seconds False 12 means the task should be run in 12 seconds You can override this to decide the interval at runtime but keep in mind the value of CELERYBEAT_MAX_LOOP_INTERVAL which decides the maximum number of seconds celerybeat can sleep between re checking the periodic task intervals So if you dynamically change the next run at value and the max interval is set to 5 minutes it will take 5 minutes for the change to take effect so you may con sider lowering the value of CELERYBEAT_MAX_LOOP_INTERVAL if responsiveness is of importance to you now relative False 12 13 celery schedules 279 Celery Documentation Release 2 5 5 remaining_estimate last_run_at Returns when the periodic task should run next as a timedelta s
133. Added User guide section Monitoring e Added user guide section Periodic Tasks Moved from getting started periodic tasks and updated e tutorials external moved to new section community e References has been added to all sections in the documentation This makes it easier to link between documents 11 31 2 0 3 release date 2010 08 27 12 00 P M CEST 11 31 1 Fixes e celeryd Properly handle connection errors happening while closing consumers e celeryd Events are now buffered if the connection is down then sent when the connection is re established e No longer depends on the mailer package This package had a name space collision with django mailer so its functionality was replaced e Redis result backend Documentation typos Redis doesn t have database names but database numbers The default database is now 0 e inspect registered_tasks was requesting an invalid command because of a typo See issue 170 e CELERY_ROUTES Values defined in the route should now have precedence over values defined in CELERY_QUEUES when merging the two With the follow settings CELERY_QUEUES cpubound exchange cpubound routing_key cpubound CELERY_ROUTES tasks add queue cpubound routing key tasks add serializer json The final routing options for tasks add will become exchange cpubound routing_key tasks add serializer
134. AsyncResult class returned by multiprocess ing Pool map_async Added dmap and dmap_async This works like the multiprocessing Pool versions except they are tasks distributed to the celery server Example gt gt gt from celery task import dmap gt gt gt import operator gt gt gt dmap operator add 2 2 4 4 8 8 gt gt gt 4 8 16 gt gt gt from celery task import dmap_async gt gt gt import operator gt gt gt result dmap_async operator add 2 2 4 4 8 8 gt gt gt result ready False gt gt gt time sleep 1 gt gt gt result ready True gt gt gt result result 4 8 16 Refactored the task metadata cache and database backends and added a new backend for Tokyo Tyrant You can set the backend in your django settings file E g CELERY_RESULT_BACKEND CELERY_RESULT_BACKEND CELERY_RESULT_BACKEND _HOST _PORT database Uses the cache Uses the djang ache framework eyrant yt localhost Hostname for the Tokyo Tyrant erve 6657 F i 11 64 0 1 11 release date 2009 05 12 02 08 P M CET e The logging system was leaking file descriptors resulting in servers stopping with the EMFILES too many open files error fixed 242 Chapter 11 Change history Celery Documeniation Release 2 5 5 11 65 0 1 10 release date 2009 05 11 12 46 P M CET e Tasks now supports both positional argu
135. CURITY_CERT_STORE New in version 2 5 The directory containing X 509 certificates used for Message Signing Can be a glob with wildcards for example etc certs pem 3 2 22 Custom Component Classes advanced CELERYD_BOOT_STEPS This setting enables you to add additional components to the worker process It should be a list of module names with celery abstract Component classes that augments functionality in the worker 104 Chapter 3 Configuration and defaults Celery Documeniation Release 2 5 5 CELERYD_POOL Name of the pool class used by the worker You can use a custom pool class name or select one of the built in aliases processes eventlet gevent Default is processes CELERYD_AUTOSCALER New in version 2 2 Name of the autoscaler class to use Default is celery worker autoscale Autoscaler CELERYD_AUTORELOADER Name of the autoreloader class used by the worker to reload Python modules and files that have changed Default is Celery worker autoreload Autoreloader CELERYD_CONSUMER Name of the consumer class used by the worker Default is celery worker consumer Consumer CELERYD_MEDIATOR Name of the mediator class used by the worker Default is celery worker controllers Mediator CELERYD_ETA_SCHEDULER Name of the ETA scheduler class used by the worker Default is celery utils timer2 Timer or one over rided by the pool implementation 3 2 23 Periodic Task Server celerybeat CE
136. Celery Documeniation Release 2 5 5 celery utils find_module module path None imp None Version of imp find_module supporting dots celery utils first predicate iterable Returns the first element in iterable that predicate returns a True value for celery utils firstmethod method Returns a functions that with a list of instances finds the first instance that returns a value for the given method The list can also contain promises promise celery utils fun_takes_kwargs fun kwlist With a function and a list of keyword arguments returns arguments in the list which the function takes If the object has an argspec attribute that is used instead of using the inspect getargspec introspection Parameters e fun The function to inspect arguments of e kwlist The list of keyword arguments Examples gt gt gt def foo X Y logfile loglevel le ans return x y gt gt gt fun_takes_kwargs foo logfile loglevel task_id logfile loglevel gt gt gt def foo 1 X Y Kwargs gt gt gt fun_takes_kwargs foo logfile loglevel task_id logfile loglevel task_id celery utils get_cls_by_name name aliases imp None package None sep kwargs Get class by name The name should be the full dot separated path to the class modulename ClassName Example celery concurrency processes TaskPool A class name or using to
137. Celery Documeniation Release 2 5 5 exception TaskPool Pool SoftTimeLimitExceeded The soft time limit has been exceeded This exception is raised to give the task a chance to clean up class TaskPool Pool Supervisor pool body class TaskPool Pool TaskHandler taskqueue put outqueue pool body class TaskPool Pool TimeoutHandler processes cache t_soft t_hard body TaskPool Pool apply func args kwds Equivalent of apply builtin TaskPool Pool apply_asynec func args kwds callback None ac cept_callback None timeout_callback None wait forslot False error_callback None soft_timeout None timeout None Asynchronous equivalent of apply builtin Callback is called when the functions return value is ready The accept callback is called when the job is accepted to be executed Simplified the flow is like this gt gt gt if accept_callback k accept_callback gt gt gt retval func args kwds gt gt gt if callback callback retval askPool Pool close askPool Pool grow n askPool Pool imap func iterable chunksize 1 lost_worker_timeout 10 0 Equivalent of itertools imap can be MUCH slower than Pool map askPool Pool imap_unordered func iterable chunksize 1 lost_worker_timeout 10 0 Like imap method but ordering of results is arbitrary askPool Pool join askPool Pool map func iterable ch
138. Celery Documentation Release 2 5 5 Ask Solem Contributors February 04 2014 Contents Celery Documeniation Release 2 5 5 Contents Contents 1 Celery Documeniation Release 2 5 5 2 Contents CHAPTER 1 Getting Started Release 2 5 Date February 04 2014 1 1 Introduction Version 2 5 5 Web http celeryproject org Download http pypi python org pypi celery Source http github com celery celery Keywords task queue job queue asynchronous rabbitmg amqp redis python webhooks queue dis tributed e Synopsis e Overview e Example e Features e Documentation e Installation Bundles Downloading and installing from source Using the development version 1 1 1 Synopsis Celery is an open source asynchronous task queue job queue based on distributed message passing Focused on real time operation but supports scheduling as well The execution units called tasks are executed concurrently on one or more worker nodes using multiprocessing Eventlet or gevent Tasks can execute asynchronously in the background or synchronously wait until ready Celery is used in production systems to process millions of tasks every hour Celery Documentation Release 2 5 5 Celery is written in Python but the protocol can be implemented in any language It can also operate with other languages using webhooks There s also RCelery for the Ruby programming lang
139. D_SOFT_TASK_TIME_LIMIT settings Note Time limits do not currently work on Windows and other platforms that do not support the STGUSR1 signal Changing time limits at runtime New in version 2 3 You can change the soft and hard time limits for a task by using the t ime _limit remote control command Example changing the time limit for the tasks crawl_the_web task to have a soft time limit of one minute and a hard time limit of two minutes gt gt gt from celery task import control gt gt gt control time_limit tasks crawl_the_web oft 60 hard 120 reply T successfully workerl example com ok time limits Only tasks that starts executing after the time limit change will be affected 2 4 7 Max tasks per child setting New in version 2 0 With this option you can configure the maximum number of tasks a worker can execute before it s replaced by a new process This is useful if you have memory leaks you have no control over for example from closed source C extensions The option can be set using the maxtasksperchild argument to celeryd or using the CELERYD_MAX_TASKS_PER_CHILD setting 2 4 8 Autoreloading New in version 2 5 Starting celeryd with the autoreload option will enable the worker to watch for file system changes to all imported task modules imported and also any non task modules added to the CELERY_IMPORTS setting or
140. Death to Cron http tensixtyone com django and celery death to cron 7 2 5 Celery Tips http ericholscher com blog 2010 nov 2 celery tips 7 1 Resources 137 Celery Documentation Release 2 5 5 7 2 6 What s your favorite Django app http jacobian org writing favorite apps 7 2 7 Virtualenv Tips http ericholscher com blog 2010 nov 1 virtualenv tips 7 2 8 10 Tools That Make Django Better http iamseb com seb 2010 10 10 django tools 7 2 9 Distributed Task Locking in Celery http www loose bits com 2010_10_10_archive html 7 2 10 Celery Python Russian http www bitbybit ru article 2 16 7 2 11 Celery Russian http vorushin ru blog 34 celery described 7 2 12 Celery RabbitMQ and sending messages directly http blog timc3 com 2010 10 17 celery rabbitmq and sending messages directly 7 2 13 Cron dentro do Django com Celery Portugese http blog avelino us 2010 10 cron dentro do django com celery html 7 2 14 RabbitMQCeleryDjango Japanese http d hatena ne jp yuku_t 7 2 15 Kaninchen amp Schlangen RabbitMQ amp Python German http www scribd com doc 37562923 Kaninchen Schlangen RabbitMQ Python 7 2 16 Celery Eine asynchrone Task Queue nicht nur fur Django German http www scribd com doc 39203296 Celery Eine asynchrone Task Queue nicht nur fur Django 138 Chapter 7 Community Resources Celery Documeniation Release 2 5 5 7 2 17 Asynchronous Proc
141. Documentation Release 2 5 5 e auto_declare Automatically declare the default exchange at instantiation De fault is True e on_return Callback to call for undeliverable messages when the mandatory or immediate arguments to publish is used This callback needs the following signature exception exchange routing_key message Note that the producer needs to drain events to use this feature auto_declare True channel None close compression None connection declare Declare the exchange This happens automatically at instantiation if aut o_declare is enabled exchange None maybe_declare entity retry False retry_policy Declare the exchange if it hasn t already been declared during this session on_return None publish body routing_key None delivery_mode None mandatory False immediate False priority 0 content_type None content_encoding None serializer None head ers None compression None exchange None retry False retry_policy None de clare properties Publish message to the specified exchange Parameters e body Message body e routing_key Message routing key e delivery_mode See delivery_mode e mandatory Currently not supported e immediate Currently not supported e priority Message priority A number between 0 and 9 e content_type Content type Default is auto detect e content_encoding Content encoding Default is auto detect
142. ENSE for more details celery contrib rdb set_trace frame None Set breakpoint at current location or a specified frame celery contrib rdb debugger Returns the current debugger instance if any or creates a new one class celery contrib rdb Rdb host 127 0 0 1 port 6899 port_search_limit 100 port_skew 0 12 28 celery events e celery events j 12 28 1 celery events H ERY_SEND_TASK_SENT_EVENT Events are messages sent for actions happening in the worker and clients if CE is enabled used for monitoring purposes copyright 3 2009 2012 by Ask Solem license BSD see LICENSE for more details celery events Event type _fields None fields Create an event An event is a dictionary the only required field is type class celery events EventDispatcher connection None hostname None enabled True chan nel None buffer_while_offline True app None serial izer None Send events as messages Parameters connection Connection to the broker hostname Hostname to identify ourselves as by default uses the hostname returned by socket gethostname enabled Set to False to not actually publish any events making send a noop opera tion channel Can be used instead of connection to specify an exact channel to use when send ing events buffer_while_offline If enabled events will be buffered while the connection is down flush mus
143. GE_TYPE settings are no longer in use This means events will not be stored until there is a consumer and the events will be gone as soon as the consumer stops Also it means there can be multiple monitors running at the same time The routing key of an event is the type of event e g workerstarted worker heartbeat task succeeded etc This means a consumer can filter on specific types to only be alerted of the events it cares about Each consumer will create a unique queue meaning it is in effect a broadcast exchange This opens up a lot of possibilities for example the workers could listen for worker events to know what workers are in the neighborhood and even restart workers when they go down or use this information to optimize tasks autoscaling Note The event exchange has been renamed from celeryevent to celeryev so it does not collide with older versions If you would like to remove the old exchange you can do so by executing the following command camgqadm exchange delete celeryevent e celeryd now starts without configuration and configuration can be specified directly on the command line Configuration options must appear after the last argument separated by two dashes celeryd 1l info I tasks broker host localhost broker vhost app e Configuration is now an alias to the original configuration so changes to the original will reflect Celery at runtime 192 Chapter 11 Change hist
144. If the worker finds an extension key it doesn t support it should optimally reject the message so another worker gets a chance to process it e taskset string The taskset this task is part of e chord object versionadded 2 3 Signifies that this task is one of the header parts of a chord The value of this key is the body of the cord that should be executed when all of the tasks in the header has returned e utc bool versionadded 2 5 If true time uses the UTC timezone if not the current local timezone should be used 13 4 3 Example message This is an example invocation of the celery task PingTask task in JSON format id 4cc7438e afd4 4f8f a2f 3 f46567e7cal7 task celery task PingTask args Diy kwargs retries 0 Teta 2009 11 17T12 30 56 527191 318 Chapter 13 Internals Celery Documeniation Release 2 5 5 13 4 4 Serialization Several types of serialization formats are supported using the content_type message header The MIME types supported by default are shown in the following table Scheme MIME Type json application json yaml application x yaml pickle application x python serialize msgpack application x msgpack 13 5 The Big Instance Refactor The app branch is a work in progress to remove the use of a global configuration in Celery Celery can now be instantiated which means several instances of Celery may exist in the same process space
145. KED READY_STATES frozenset FAILURE REVOKED SUCCESS exception The BaseBac TimeoutError operation timed out BaseBackend cleanup Backend cleanup Is run by celery task DeleteExpiredTaskMetaTask BaseBackend decode payload BaseBackend delete_taskset taskset_id BaseBackend encode data BaseBac BaseBac Con BaseBac BaseBac Get BaseBac Get BaseBac Get BaseBac kend encode_result result status kend exception_to_python exc vert serialized exception to Python exception kend forget ftask_id kend get_result task_id the result of a task kend get_status task_id the status of a task kend get_traceback fask_id the traceback for a failed task kend mark_as_done task_id result Mark task as successfully executed BaseBac kend mark_as_ failure task_id exc traceback None Mark task as executed with failure Stores the execption BaseBac kend mark_as_retry task_id exc traceback None Mark task as being retries Stores the current exception if any BaseBac BaseBac kend mark_as_revoked task_id kend mark_as_started task_id meta Mark a task as started BaseBac BaseBac kend on_chord_apply setid body result None kwargs kend on_chord_part_return task propagate False 352 Chapter 13 kend UNREADY_STATES frozenset STARTED RECEIVED RETRY PENDING Cel
146. LERYBEAT_SCHEDULE The periodic task schedule used by celerybeat See Entries CELERYBEAT_SCHEDULER The default scheduler class Default is celery beat PersistentScheduler Can also be set via the S argument to celerybeat 3 2 Configuration Directives 105 Celery Documeniation Release 2 5 5 CELERYBEAT_SCHEDULE_FILENAME Name of the file used by PersistentScheduler to store the last run times of periodic tasks Can be a relative or absolute path but be aware that the suffix db may be appended to the file name depending on Python version Can also be set via the schedule argument to celerybeat CELERYBEAT_MAX_LOOP_INTERVAL The maximum number of seconds celerybeat can sleep between checking the schedule Default is 300 seconds 5 minutes 3 2 24 Monitor Server celerymon CELERYMON_LOG_FORMAT The format to use for log messages Default is asctime s levelname s processName s message s See the Python logging module for more information about log formats 3 2 25 Deprecated Settings These settings have been deprecated and should no longer used as they will be removed in future versions CELERY_AMQP_TASK_RESULT_EXPIRES Deprecated since version 2 5 The time in seconds of which the task result queues should expire This setting is deprecated and will be removed in version 3 0 Please use CELERY_TASK_RESULT_EXPIRES instead Note AMQP result expiration require
147. LERYD_PID_FILE CELERY BEAT_PID_FILE CELERYMON_PID_FILE e Default celeryd loglevel is now WARN to enable the previous log level start celeryd with loglevel INFO e Tasks are automatically registered This means you no longer have to register your tasks manually You don t have to change your old code right away as it doesn t matter if a task is registered twice If you don t want your task to be automatically registered you can set the abstract attribute class MyTask Task abstract By using abstract only tasks subclassing this task will be automatically registered this works like the Django ORM If you don t want subclasses to be registered either you can set the autoregister attribute to False Incidentally this change also fixes the problems with automatic name assignment and relative im ports So you also don t have to specify a task name anymore if you use relative imports e You can no longer use regular functions as tasks 228 Chapter 11 Change history Celery Documeniation Release 2 5 5 This change was added because it makes the internals a lot more clean and simple However you can now turn functions into tasks by using the task decorator from celery decorators import task task def add x y return x y See also Tasks for more information about the task decorators e The periodic task system has been rewritten to a centralized solution This means celeryd no longer schedul
148. Now syncs the schedule to disk when receiving the SIGTERM and SIGINT signals e Control commands Make sure keywords arguments are not in Unicode e ETA scheduler Was missing a logger object so the scheduler crashed when trying to log that a task had been revoked management commands camqadm Fixed typo camqpadm gt camqadm Issue 83 e PeriodicTask delta_resolution Was not working for days and hours now fixed by rounding to the nearest day hour e Fixed a potential infinite loop in BaseAsyncResult __eq triggered although there is no evidence that it has ever been 11 39 1 0 2 225 Celery Documentation Release 2 5 5 e celeryd Now handles messages with encoding problems by acking them and emitting an error message 11 40 1 0 1 release date 2010 02 24 07 05 P M CET e Tasks are now acknowledged early instead of late This is done because messages can only be acknowledged within the same connection channel so if the connection is lost we would have to refetch the message again to acknowledge it This might or might not affect you but mostly those running tasks with a really long execution time are affected as all tasks that has made it all the way into the pool needs to be executed be fore the worker can safely terminate this is at most the number of pool workers multiplied by the CELERYD_PREFETCH_MULTIPLIER setting We multiply the prefetch count by default to increase the per
149. O and stacktraces are dumped Thanks to Gr goire Cachet Make every new worker process re establish it s Django DB connection this solving the MySQL connection died exceptions Thanks to Vitaly Babiy and Jirka Vejrazka IMPORTANT Now using pickle to encode task arguments This means you now can pass complex python objects to tasks as arguments Removed dependency to yadayada Added a FAQ see docs faq rst Now converts any Unicode keys in task kwargs to regular strings Thanks Vitaly Babiy Renamed the TaskDaemon to WorkController celery datastructures TaskProcessQueue is now renamed to celery pool TaskPool The pool algorithm has been refactored for greater performance and stability 11 56 0 2 0 release date 2009 05 20 05 14 P M CET Final release of 0 2 0 240 Chapter 11 Change history Celery Documentation Release 2 5 5 e Compatible with carrot version 0 4 0 e Fixes some syntax errors related to fetching results from the database backend 11 57 0 2 0 pre3 release date 2009 05 20 05 14 P M CET e Internal release Improved handling of unpickleable exceptions get_result now tries to recreate something looking like the original exception 11 58 0 2 0 pre2 release date 2009 05 20 01 56 P M CET e Now handles unpickleable exceptions like the dynamically generated subclasses of django core exception MultipleObjectsReturned 11 59 0 2 0 pre1 release date 2009 05 20 12 33 P M CET e It s gett
150. PS myapp 2 2 Tasks 25 Celery Documentation Release 2 5 5 This makes more sense from the reusable app perspective anyway 2 2 7 Decorating tasks When using other decorators you must make sure that the task decorator is applied last task decorator2 decoratorl def add x y return x y Which means the task decorator must be the top statement 2 2 8 Task States Celery can keep track of the tasks current state The state also contains the result of a successful task or the exception and traceback information of a failed task There are several result backends to choose from and they all have different strengths and weaknesses see Result Backends During its lifetime a task will transition through several possible states and each state may have arbitrary metadata attached to it When a task moves into a new state the previous state is forgotten about but some transitions can be deducted e g a task now in the FAILED state is implied to have been in the STARTED state at some point There are also sets of states like the set of FAILURE_STATES and the set of READY_STATES The client uses the membership of these sets to decide whether the exception should be re raised PROPAGATE_STATES or whether the state can be cached it can if the task is ready You can also define Custom states Result Backends Celery needs to store or send the states somewhere The
151. Q 1 3 images video Q 4 5 data Q default L 4 5 DEBUG Additional options are added to each celeryd but you can also modify the options for ranges of or specific workers 3 workers Two with 3 processes and one with 10 processes celeryd multi start 3 c 3 c 1 10 leryd n celerydl myhost c 10 leryd n celeryd2 myhost c 3 leryd n celeryd3 myhost c 3 can also specify options for named workers celeryd multi start image video data c 3 c image 10 leryd n image myhost c 10 leryd n video myhost c 3 celeryd n data myhost c 3 QQ OOO Ur ranges and lists of workers in options is also allowed c 1 3 can also be written as c 1 2 3 celeryd multi start 5 c 3 c 1 3 10 leryd n celerydl myhost c 10 leryd n celeryd2 myhost c 10 leryd n celeryd3 myhost c 10 leryd n celeryd4 myhost c 3 leryd n celeryd5 myhost c 3 12 38 celery bin celeryd_multi 307 Celery Documentation Release 2 5 5 lists also works with named workers celeryd multi start foo bar baz xuzzy c 3 c foo bar baz 10 celeryd n foo myhost c 10 celeryd n bar myhost c 10 celeryd n baz myhost c 10 celeryd n xuzzy myhost c 3 class celery bin celeryd_multi MultiTool env None fh None error msg None execute_from_commandline argv cmd celeryd expand argv cnd None get argv cmd getpids p cmd callback None help argv cmd None info ms
152. Release 2 5 5 7 2 28 Using Python magic to improve the deferred API http blog notdot net 2010 06 Using Python magic to improve the deferred API 7 2 29 How Celery Carrot and your messaging stack work http jasonmbaker com how celery carrot and your messaging stack wo 7 2 30 Large Problems in Django Mostly Solved Delayed Execution http ericholscher com blog 2010 jun 23 large problems django mostly solved delayed execut 7 2 31 Introduction to Celery Awesome slides from when Idan Gazit had a talk about Celery at PyWeb IL http www slideshare net idangazit an introduction to celery 7 2 32 RabbitMQ Celery and Django Great Celery tutorial by Robert Pogorzelski at his blog Happy Stream of Thoughts http robertpogorzelski com blog 2009 09 10 rabbitmq celery and django 7 2 33 Message Queues Django and Celery Quick Start Celery tutorial by Rich Leland the installation section is Mac OS X specific http mathematism com 2010 feb 16 message queues django and celery quick start 7 2 34 Background task processing and deferred execution in Django Alon Swartz writes about celery and RabbitMQ on his blog http www turnkeylinux org blog django celery rabbitmq 7 2 35 Build a processing queue in less than a day using RabbitMQ and Celery Tutorial in 2 parts written by Tim Bull http timbull com build a processing queue with multi threading 7 2 36 How to get celeryd to work on FreeBSD Installing multip
153. S CXC 138 10r MIs 16 4 kernel ERTS CXC 138 10 2 13 4 nodes rabbit myhost running_nodes rabbit myhost done This is especially important if your DHCP server gives you a host name starting with an IP address e g 23 10 112 31 comcast net because then RabbitMQ will try to use rabbit 23 which is an illegal host name Starting Stopping the RabbitMQ server To start the server sudo rabbitmq server you can also run it in the background by adding the detached option note only one dash sudo rabbitmq server detached Never use kill to stop the RabbitMQ server but rather use the rabbitmqctl command sudo rabbitmqctl stop When the server is running you can continue reading Setting up RabbitMQ 8 Chapter 1 Getting Started Celery Documeniation Release 2 5 5 1 2 2 Using Redis Installation For the Redis support you have to install additional dependencies You can install both Celery and these dependencies in one go using ehter the celery with redis or the django celery with redis bundles pip install U celery with redis Configuration Configuration is easy set the transport and configure the location of your Redis database BROKER_URL redis localhost 6379 0 Where the URL is in the format of redis userid password hostname port db_number Results If you also want to store the state and return values of tasks in Redis you should
154. The task consumer class used Default is kombu compat Consumer ConsumerSet The class used to consume from multiple queues using the same channel queues All currently defined task queues A Queues instance Queues queues Create new Queues instance using queue defaults from the current configuration Router queues None create_missing None Returns the current task router TaskConsumer args kwargs Returns consumer for a single task queue TaskPublisher args kwargs Returns publisher used to send tasks You should use app send_task instead get_task_consumer connection queues None kwargs Return consumer configured to consume from all known task queues get_default_queue Returns queue_name queue_options tuple for the queue configured to be default CELERY_DEFAULT_QUEUE 12 3 2 Queues class celery app amqp Queues queues Queue name declaration mapping Celery will consult this mapping to find the options for any queue by name Parameters queues Initial mapping add queue exchange None routing_key None exchange_type direct options Add new queue Parameters e queue Name of the queue e exchange Name of the exchange e routing_key Binding key e exchange_type Type of exchange e options Additional declaration options 256 Chapter 12 API Reference Celery Documeniation Release 2 5 5 options exchange routing_key
155. This is normal operation and always happens unless the throw argument to retry is set to False Using a custom retry delay When a task is to be retried it will wait for a given amount of time before doing so The default delay is in the default_retry_delay attribute on the task By default this is set to 3 minutes Note that the unit for setting the delay is in seconds int or float You can also provide the countdown argument to ret ry to override this default task default_retry_delay 30 60 et n 30 minutes def add x y try except Exception exc add retry exc exc countdown 60 22 Chapter 2 User Guide Celery Documeniation Release 2 5 5 2 2 5 Task options General Task name The name the task is registered as You can set this name manually or just use the default which is automatically generated using the module and class name See Task names Task abstract Abstract classes are not registered but are used as the base class for new task types Task max_retries The maximum number of attempted retries before giving up If this exceeds the MaxRetriesExceeded an exception will be raised NOTE You have to ret ry manually it s not something that happens automatically Task default_retry delay Default time in seconds before a retry of the task should be executed Can be either int or float Default is a 3 minute delay Task rate_limit Set the rate limit for this task type i e how many
156. You need to add the same arguments when you restart as these are not persisted anywhere e Examples j 306 Chapter 12 API Reference Celery Documeniation Release 2 5 5 wn oe QqQaQqaqQq 1 ec fe celeryd multi restart Lesli E pidfile var run celery n pid logfile var run celery n log To stop the node you need to specify the same pidfile celeryd multi stop Lesli pidfile var run celery n pid 3 workers with 3 processes each celeryd multi start 3 c 3 leryd n celerydl myhost c 3 w leryd n celeryd2 myhost c leryd n celeryd3 myhost c 3 start 3 named workers celeryd multi start image video data c 3 leryd n image myhost c 3 leryd n video myhost c 3 celeryd n data myhost c 3 U H Se SR SE a Qa UH se oe 3 QqQaQqaQ W 3 c specify custom hostname celeryd multi start 2 n worker example com c 3 leryd n celerydl worker example com c 3 leryd n celeryd2 worker example com c 3 Advanced example starting 10 workers in the background x Thr of the workers processes the images and video queue x Two of the workers processes the data queue with loglevel DEBUG x the rest processes the default queue celeryd multi start 10 1 INFO Q 1 3 images video Q 4 5 data Q default L 4 5 DEBUG You can show the commands necessary to start the workers with the show command celeryd multi show 10 1 INFO
157. _failure If you need more flexibility then you can use objects instead of a dict to choose which tasks to annotate class MyAnnotate object def annotate self task if task name startswith tasks return rate_limit 10 s CELERY_ANNOTATIONS MyAnnotate 3 2 4 Concurrency settings CELERYD_CONCURRENCY The number of concurrent worker processes threads green threads executing tasks Defaults to the number of available CPUs CELERYD_PREFETCH_MULTIPLIER How many messages to prefetch at a time multiplied by the number of concurrent processes The default is 4 four messages for each process The default setting is usually a good choice however if you have very long running tasks waiting in the queue and you have to start the workers note that the first worker to start will receive four times the number of messages initially Thus the tasks may not be fairly distributed to the workers 3 2 5 Task result backend settings CELERY_RESULT_BACKEND Deprecated aliases CELERY_BACKEND The backend used to store task results tombstones Disabled by default Can be one of the following e database Use a relational database supported by SQLAIchemy See Database backend settings e cache Use memcached to store the results See Cache backend settings e mongodb Use MongoDB to store the results See MongoDB backend settings e redis Use Redis to store the results See Redis backend se
158. _ready consumer OSx_proxy_detection_workaround See http github com celery celery issues issue 161 purge_messages redirect_stdouts None redirect_stdouts_level None redirect_stdouts_to_logger run run_worker set_process_ status info startup_info tasklist include_builtins True worker_init lery apps worker cpu_count lery apps worker get_process_name lery apps worker install_HUP_not_supported_handler worker lery apps worker install_cry_handler logger 12 30 celery apps worker 297 Celery Documentation Release 2 5 5 celery apps worker install_rdb_ handler envvar CELERY_RDBSIG celery apps worker install_worker_int_again_handler worker celery apps worker install_worker_int_handler worker celery apps worker install_worker_restart_handler worker celery apps worker install_worker_term_handler worker celery apps worker install_worker_term_hard_handler worker 12 31 celery apps beat class celery apps beat Beat max_interval None app None socket_timeout 30 pidfile None kwargs class Service logger None max_interval None schedule_filename None scheduler_cls None app None get_scheduler lazy False scheduler scheduler_cls alias of PersistentScheduler start embedded_process False stop wait False sync Beat init_loader Beat install_sync_handler beat Install a SIGTERM SIGINT handler that saves the ce
159. _run_at Returns tuple of two items is_due next_time_to_run where next time to run is in seconds See celery schedules schedule is_due for more information remaining_estimate last_run_at Returns when the periodic task should run next as a timedelta timedelta_seconds delta Convert timedelta to seconds Doesn t account for negative timedeltas class celery task base TaskType Meta class for tasks 12 6 celery task base 265 Celery Documentation Release 2 5 5 Automatically registers the task in the task registry except if the abstract attribute is set If no name attribute is provided then no name is automatically set to the name of the module it was defined in and the class name 12 7 celery task sets e celery task sets j 12 7 1 celery task sets Creating and applying groups of tasks copyright 3 2009 2012 by Ask Solem license BSD see LICENSE for more details class celery task sets TaskSet tasks None app None Publisher None A task containing several subtasks making it possible to track how many or when all of the tasks have been completed Parameters tasks A list of subtask instances Example gt gt gt urls http cnn com rss http bbc co uk rss gt gt gt taskset TaskSet refresh_feed subtask url for url in urls gt gt gt taskset_result taskset apply_async gt gt gt list_of_return_values taskset_result Jjoin apply taskset_
160. _trace lt set breakpoint return result 143 Celery Documeniation Release 2 5 5 set_trace sets a breakpoint at the current location and creates a socket you can telnet into to remotely debug your task The debugger may be started by multiple processes at the same time so rather than using a fixed port the debugger will search for an available port starting from the base port 6900 by default The base port can be changed using the environment variable CELERY _RDB_ PORT By default the debugger will only be available from the local host to enable access from the outside you have to set the environment variable CELERY_RDB_HOST When celeryd encounters your breakpoint it will log the following information INFO MainProcess Got task from broker tasks add d7261c71 4962 47e5 b342 2448bedd20e8 WARNING PoolWorker 1 Remote Debugger 6900 Please telnet 127 0 0 1 6900 Type exit in session to continue 2011 01 18 14 25 44 119 WARNING PoolWorker 1 Remote Debugger 6900 Waiting for client If you telnet the port specified you will be presented with a pdb shell telnet localhost 6900 Connected to localhost Escape character is gt opt devel demoapp tasks py 128 add gt return result Pdb Enter help to get a list of available commands It may be a good idea to read the Python Debugger Manual if you have never used pdb before To demonstrate we will re
161. _weakref target on_delete Instantiates the appropiate BoundMet hodWeakRef depending on the details of the underlying class method implementation celery utils dispatch saferef safe_ref target on_delete None Return a safe weak reference to a callable target Parameters e target the object to be weakly referenced if it s a bound method reference will create a BoundMet hodWeakref otherwise creates a simple weakref ref e on_delete if provided will have a hard reference stored to the callable to be called after the safe reference goes out of scope with the reference object either a weakref ref ora BoundMethodWeakref as argument 13 6 57 celery platforms e celery platforms I celery platforms Utilities dealing with platform specifics signals daemonization users groups and so on copyright 3 2009 2012 by Ask Solem license BSD see LICENSE for more details class celery platforms DaemonContext pidfile None workdir None umask None fake False kwargs close args open umask 0 workdir exception celery platforms LockFailed Raised if a pidlock can t be acquired class celery platforms PIDFile path PID lock file This is the type returned by create_pidlock Should not be used directly use the func create_pidlock context instead acquire Acquire lock is_locked Returns true if the pid lock exists path None Path to the pid lock file read_pid
162. a configuration file or just add last minute options on the command line Example use celeryd multi start 4 c 2 broker host amqp example com__broker vhost cel ery disable_rate_limits yes celerybeat Now retries establishing the connection Issue 419 celeryctl New list bindings command Lists the current or all available bindings depending on the broker transport used Heartbeat is now sent every 30 seconds previously every 2 minutes ResultSet join_native and iter_native is now supported by the Redis and Cache result backends This is an optimized version of join using the underlying backends ability to fetch multiple results at once Can now use SSL when sending error e mails by enabling the EMATL_USE_SSL setting events default_dispatcher Context manager to easily obtain an event dispatcher instance using the connection pool Import errors in the configuration module will not be silenced anymore 182 Chapter 11 Change history Celery Documeniation Release 2 5 5 ResultSet iterate Now supports the timeout propagate and interval arguments with_default_connection gt with default_connection TaskPool apply_async Keyword arguments callbacks and errbacks has been renamed to callback and errback and take a single scalar value instead of a list No longer propagates errors occurring during process cleanup Issue 365 Added TaskSetResult delete which will delete a previous
163. access to the task class gt gt gt from celery execute import send_task gt gt gt result send_task tasks add 2 2 gt gt gt result get 4 2 3 2 ETA and countdown The ETA estimated time of arrival lets you set a specific date and time that is the earliest time at which your task will be executed countdown is a shortcut to set eta by seconds into the future gt gt gt result add apply_async args 10 10 countdown 3 gt gt gt result get this takes at least 3 2COr t 0 The task is guaranteed to be executed at some time after the specified date and time but not necessarily at that exact time Possible reasons for broken deadlines may include many items waiting in the queue or heavy network latency To make sure your tasks are executed in a timely manner you should monitor queue lengths Use Munin or similar tools to receive alerts so appropriate action can be taken to ease the workload See Munin While countdown is an integer eta must be a dat et ime object specifying an exact date and time including mil lisecond precision and timezone information gt gt gt from datetime import datetime timedelta gt gt gt tomorrow datetime now timedelta days 1 gt gt gt add apply_async args 10 10 eta tomorrow 2 3 3 Expiration The expires argument defines an optional expiry time either as seconds after task publish or a specific date and time using datetime gt gt gt Task
164. ace mro_lookup cls attr stop Returns the first node by MRO order that defines an attribute Parameters stop A list of types that if reached will stop the search Returns None if the attribute was not found celery execute trace report_internal_error task exc celery execute trace trace_task task uuid args kwargs request None opts 366 Chapter 13 Internals Celery Documeniation Release 2 5 5 13 6 31 celery app abstract class celery app abstract configurated confopts_as_dict setup_defaults kwargs namespace celery class celery app abstract from_config key None get_key atir 13 6 32 celery app annotations class celery app annotations MapAnnotation annotate task annotate_any celery app annotations prepare annotations Expands the CELERY_ANNOTATIONS setting 13 6 33 celery security certificate class celery security certificate CertStore Base class for certificate stores add_cert cert itercerts an iterator over the certificates class celery security certificate Certificate cert X 509 certificate get_id Serial number issuer pair uniquely identifies a certificate get_issuer Returns issuer CA as a string get_serial_number Returns the certificates serial number has_expired Check if the certificate has expired verify data signature digest Verifies the signature for string containing data class celery securit
165. ack for the task retried event on_revoked timestamp None fields Callback for the task revoked event on_sent timestamp None fields Callback for the task sent event on_started timestamp None fields Callback for the task started event on_succeeded timestamp None fields Callback for the task succeeded event on_unknown_event type timestamp None fields ready update state timestamp fields Update state from new event Parameters e state State from event e timestamp Timestamp from event fields Event data class celery events state Worker fields Worker State alive 12 29 celery events state 295 Celery Documentation Release 2 5 5 heartbeat_max 4 on_heartbeat timestamp None kwargs Callback for the worker heartbeat event on_offline kwargs Callback for the worker offline event on_online timestamp None kwargs Callback for the worker online event 12 30 celery apps worker class celery apps worker Worker hostname None discard False embed_clockservice False queues None include None app None pidfile None au toscale None autoreload False kwargs class WorkCont roller loglevel None hostname None logger None ready_callback lt function noop at OxIcaf668 gt queues None app None kwargs Unmanaged worker instance CLOSE 2 RUN 1 TERMINATE 3 autoreloader_cl1s None autoscaler_cls None concurr
166. ad the value of the result variable change it and continue execution of the task Pdb result 4 Pdb result hello from rdb Pdb continue Connection closed by foreign host The result of our vandalism can be seen in the worker logs 2011 01 18 14 35 36 599 INFO MainProcess Task tasks add d7261c71 4962 47e5 b342 2448bedd20e8 succeeded in 61 481s hello from rdb 8 2 2 Tips Enabling the breakpoint signal If the environment variable CELERY_RDBSTIG is set the worker will open up an rdb instance whenever the SIGUSR2 signal is sent This is the case for both main and worker processes For example starting the worker with CELERY_RDBSIG 1 celeryd 1 info You can start an rdb session for any of the worker processes by executing 144 Chapier 8 Tutorials Celery Documentation Release 2 5 5 kill USR2 lt pid gt 8 3 Tutorial Creating a click counter using Kombu and celery e Introduction e The model e Using Kombu to send clicks as messages e View and URLs e Creating the periodic task e Finishing 8 3 1 Introduction A click counter should be easy right Just a simple view that increments a click in the DB and forwards you to the real destination This would work well for most sites but when traffic starts to increase you are likely to bump into problems One database write for every click is not good if you have millions of clicks a day So what can yo
167. al The return value of the task 82 Chapter 2 User Guide Celery Documeniation Release 2 5 5 task_failure Dispatched when a task fails Sender is the task class executed Provides arguments e task_id Id of the task e exception Exception instance raised e args Positional arguments the task was called with e kwargs Keyword arguments the task was called with e traceback Stack trace object e einfo The celery datastructures ExceptionInfo instance Worker Signals celeryd_init This is the first signal sent when celeryd starts up The sender is the host name of the worker so this signal can be used to setup worker specific configuration from celery signals import celeryd_init celeryd_init connect sender workerl2 example com def configure_worker12 conf le kkwargs conf CELERY_DEFAULT_RATE LIMIT 10 m or to set up configuration for multiple workers you can omit specifying a sender when you connect from celery signals import celeryd_init celeryd_init connect def configure_workers sender conf xkKwargs if sender in workerl example com worker2 example com conf CELERY_DEFAULT_RATE_LIMIT 10 m if sender worker3 example com conf CELERYD_PREFETCH_MULTIPLIER 0 Provides arguments e instance This is the celery apps worker Worker instance to be initialized Note that only the app and hostname attributes have b
168. alue should be based on the number of active threads greenthreads using broker connections 2 11 4 Worker Settings Prefetch Limits Prefetch is a term inherited from AMQP that is often misunderstood by users The prefetch limit is a limit for the number of tasks messages a worker can reserve for itself If it is zero the worker will keep consuming messages not respecting that there may be other available worker nodes that may be able to process them sooner or that the messages may not even fit in memory 78 Chapter 2 User Guide Celery Documeniation Release 2 5 5 The workers default prefetch count is the CELERYD_PREFETCH_MULTIPLIER setting multiplied by the number of child worker processes If you have many tasks with a long duration you want the multiplier value to be 1 which means it will only reserve one task per worker process at a time However If you have many short running tasks and throughput round trip latency is important to you this number should be large The worker is able to process more tasks per second if the messages have already been prefetched and is available in memory You may have to experiment to find the best value that works for you Values like 50 or 150 might make sense in these circumstances Say 64 or 128 If you have a combination of long and short running tasks the best option is to use two worker nodes that are configured separately and route the task
169. am master With this option you don t clutter the history with merging commit notes See Rebasing merge commits in git If you want to learn more about rebasing see the Rebase section in the Github guides If you need to work on a different branch than master you can fetch and checkout a remote branch like this git checkout track b 3 0 devel origin 3 0 devel For a list of branches see Branches 6 6 2 Running the unit test suite To run the Celery test suite you need to install a few dependencies A complete list of the dependencies needed are located in requirements test txt Installing the test requirements pip E SVIRTUAL_ENV install U r requirements test txt When installation of dependencies is complete you can execute the test suite by calling nosetests nosetests Some useful options to nosetests are ee Stop running the tests at the first test that fails Don t capture output e nologcapture Don t capture log output Run with verbose output If you want to run the tests for a single test file only you can do so like this nosetests celery tests test_worker test_worker_job 6 6 3 Creating pull requests When your feature bugfix is complete you may want to submit a pull requests so that it can be reviewed by the maintainers Creating pull requests is easy and also let you track the progress of your contribution Read the Pull Requests section in the Github Guide to learn how this
170. an be added to task modules or you can keep them in their own module then import them using the CELERY_IMPORTS setting CELERY_IMPORTS myapp worker control 2 4 10 Inspecting workers celery task control inspect lets you inspect running workers It uses remote control commands under the hood gt gt gt from celery task control import inspect Inspect all nodes gt gt gt i inspect Specify multiple nodes to inspect gt gt gt i inspect workerl example com worker2 example com Specify a single node to inspect gt gt gt i inspect workerl example com Dump of registered tasks You can get a list of tasks registered in the worker using the registered 48 Chapter 2 User Guide Celery Documeniation Release 2 5 5 gt gt gt i registered workerl example com celery delete_expired_task_meta celery execute_remote celery map_async celery ping celery task http HttpDispatchTask tasks add tasks sleeptask Dump of currently executing tasks You can get a list of active tasks using active gt gt gt L active workerl example com name tasks sleeptask id 32666e9b 809c 41fa 8e93 5ae0c80afbbEt Targas 8 y kwargs Dump of scheduled ETA tasks You can get a list of tasks waiting to be scheduled by using scheduled gt gt gt 1 scheduled worke
171. an drop a Python module in the users directory that executes arbitrary com mands This was the original reason not to do this but if done only when loading the config module this means that the behavior will only apply to the modules imported in the config module which I think is a good compromise certainly better than just explicitly setting PYTHONPATH anyway Experimental Cassandra backend added celeryd SIGHUP handler accidentally propagated to worker pool processes In combination with 7a7c44e39344789f1 1b5346e9cc8340f5fe4846c this would make each child pro cess start a new celeryd when the terminal window was closed celeryd Do not install SIGHUP handler if running from a terminal This fixes the problem where celeryd is launched in the background when closing the terminal celeryd Now joins threads at shutdown See issue 152 Test tear down Don t use atexit but nose s teardown functionality instead See issue 154 Debian init script for celeryd Stop now works correctly Task logger warn method added synonym for warning Can now define a white list of errors to send error emails for Example CELERY_TASK_ERROR_WHITELIST myapp MalformedInputError See issue 153 celeryd Now handles overflow exceptions in time mktime while parsing the ETA field LoggerWrapper Try to detect loggers logging back to stderr stdout making an infinite loop Added celery task control
172. an now be used as a decorator Example from celery signals import task_sent task_sent connect def on_task_sent kwargs print sent task Sr kwargs e Invalid task messages are now rejected instead of acked This means that they will be moved to the dead letter queue introduced in the latest RabbitMQ version but must be enabled manually consult the RabbitMQ documentation 11 1 2 5 5 171 Celery Documentation Release 2 5 5 e Internal logging calls has been cleaned up to work better with tools like Sentry Contributed by David Cramer e New method subtask clone can be used to clone an existing subtask with augmented arguments options Example gt gt gt s add subtask 5 gt gt gt new s clone args 10 countdown 5 gt gt gt new args 10 5 gt gt gt new options countdown 5 e Chord callbacks are now triggered in eager mode 11 3 2 Fixes e Programs now verifies that the pidfile is actually written correctly Issue 641 Hopefully this will crash the worker immediately if the system is out of space to store the complete pidfile In addition we now verify that existing pidfiles contain a new line so that a partially written pidfile is detected as broken as before doing echo n 1 gt celeryd pid would cause celeryd to think that an existing instance was already running init has pid 1 after all e Fixed 2 5 compatibility issue with use of print_except
173. ance of a receiver This will usually be a string though it may be anything hashable disconnect receiver None sender None weak True dispatch_uid None Disconnect receiver from sender for signal If weak references are used disconnect need not be called The receiver will be removed from dispatch automatically Parameters e receiver The registered receiver to disconnect May be none if dispatch_uid is specified e sender The registered sender to disconnect e weak The weakref state to disconnect e dispatch_uid the unique identifier of the receiver to disconnect send sender named Send signal from sender to all connected receivers If any receiver raises an error the error propagates back through send terminating the dispatch loop so it is quite possible to not have all receivers called if a raises an error Parameters e sender The sender of the signal Either a specific object or None e named Named arguments which will be passed to receivers Returns a list of tuple pairs receiver response send_robust sender named Send signal from sender to all connected receivers catching errors Parameters e sender The sender of the signal Can be any python object normally one registered with a connect if you actually want something to occur e named Named arguments which will be passed to receivers These argu ments must be a subset of the argument names defined in providing_args
174. and these depen dencies in one go using either the celery with beanstalk or the django celery with beanstalk bundles pip install U celery with beanstalk Configuration Configuration is easy set the transport and configure the location of your CouchDB database BROKER_URL beanstalk localhost 11300 Where the URL is in the format of beanstalk hostname port The host name will default to Localhost and the port to 11300 and so they are optional Results Using Beanstalk to store task state and results is currently not supported Limitations The Beanstalk message transport does not currently support e Remote control commands celeryctl broadcast e Authentication 1 3 First steps with Celery e Choosing your Broker e Creating a simple task e Configuration e Running the celery worker server e Executing the task Keeping Results e Where to go from here 12 Chapter 1 Getting Started Celery Documeniation Release 2 5 5 1 3 1 Choosing your Broker Before you can use Celery you need to choose install and run a broker The broker is the service responsible for receiving and delivering task messages There are several choices available including e Using RabbitMQ RabbitMQ is feature complete safe and durable If not losing tasks is important to you then this is your best option e Using Redis Redis is also feature complete but power failures or abrupt termination may result in data lo
175. ange queue binding The routing key is treated 13 6 Internal Module Reference 357 Celery Documentation Release 2 5 5 2099 as zero or more words delimited by and supports special wild card characters matches a single word and matches zero or more words efanout Queues are bound to this exchange with no arguments Hence any message sent to this exchange will be forwarded to all queues bound to this exchange eheaders Queues are bound to this exchange with a table of arguments con taining headers and values optional A special argument named x match determines the matching algorithm where all implies an AND all pairs must match and any implies OR at least one pair must match arguments is used to specify the arguments This description of AMQP exchange types was shamelessly stolen from the blog post AMQP in 10 minutes Part 4 by Rajith Attapattu This article is recommended reading channel The channel the exchange is bound to if bound durable Durable exchanges remain active when a server restarts Non durable exchanges transient ex changes are purged when a server restarts Default is True auto_delete If set the exchange is deleted when all queues have finished using it Default is False delivery_mode The default delivery mode used for messages The value is an integer or alias string e or transient The message is transient Which means it is sto
176. ans workers running versions pre 2 5 will be out of sync with upgraded workers To enable UTC you have to set CELERY_ENABLE_UTC CELERY_ENABLE_UTC T When UTC is enabled dates and times in task messages will be converted to UTC and then converted back to the local timezone when received by a worker You can change the local timezone using the CELERY_TIMEZONE setting Installing the pytz library is recom mended when using a custom timezone to keep timezone definition up to date but it will fallback to a system defini tion of the timezone if available UTC will enabled by default in version 3 0 Note django celery will use the local timezone as specified by the TIME_ZONE setting it will also honor the new USE_TZ setting introuced in Django 1 4 10 4 2 New security serializer using cryptographic signing A new serializer has been added that signs and verifies the signature of messages The name of the new serializer is auth and needs additional configuration to work see Security See also 10 3 Deprecations 163 Celery Documentation Release 2 5 5 Security Contributed by Mher Movsisyan 10 4 3 Experimental support for automatic module reloading Starting celeryd with the autoreload option will enable the worker to watch for file system changes to all imported task modules imported and also any non task modules added to the CELERY_IMPORTS se
177. applications The application default can be overridden with the CELERY_ACKS_LATE setting BaseTask after_return status retval task_id args kwargs einfo Handler called after the task returns 12 2 celery app task 249 Celery Documentation Release 2 5 5 Parameters status Current task state retval Task return value exception task_id Unique id of the task args Original arguments for the task that failed kwargs Original keyword arguments for the task that failed einfo Except ionInfo instance containing the traceback if any The return value of this handler is ignored BaseTask app None The application instance associated with this task class classmethod BaseTask apply args None kwargs None options Execute this task locally by blocking until the task returns Parameters args positional arguments passed on to the task kwargs keyword arguments passed on to the task throw Re raise task exceptions Defaults to the CELERY_EAGER_PROPAGATES_EXCEPTIONS setting atype celery result EagerResult classmethod BaseTask apply_async args None kwargs None task_id None publisher None connection None router None queues None options Apply tasks asynchronously by sending a message Parameters args The positional arguments to pass on to the task a list or tuple kwargs The keyword argum
178. args kwargs options subtask is actually a dict subclass which means it can be serialized with JSON or other encodings that doesn t support complex Python objects Also it can be regarded as a type as the following usage works 2 6 Sets of tasks Subtasks and Callbacks 53 Celery Documentation Release 2 5 5 gt gt gt s subtask tasks add args 2 2 kwargs gt gt gt subtask s coerce dict int This makes it excellent as a means to pass callbacks around to tasks Callbacks Let s improve our add task so it can accept a callback that takes the result as an argument from celery task import task from celery task sets import subtask task def add x y callback de result x y if callback is not subtask callback delay result return result subtask also knows how it should be applied asynchronously by delay and eagerly by apply The best thing is that any arguments you add to subtask delay will be prepended to the arguments specified by the subtask itself If you have the subtask gt gt gt add subtask args 10 subtask delay result becomes gt gt gt add apply_async args result 10 Now let s execute our new add task with a callback gt gt gt add delay 2 2 callback add subtask 8 As expected this will first launch one task calculating 2 2 then another task calculating 4 8 2 6 2 Task Sets The TaskSet enables easy invocation of s
179. argument to apply_async 2 The tasks serializer attribute 3 The default CELERY_TASK_SERIALIZER setting e Using the serializer argument to apply_async 2 3 Executing Tasks 39 Celery Documentation Release 2 5 5 gt gt gt add apply_async args 10 10 serializer json 2 3 5 Connections and connection timeouts Automatic Pool Support Since version 2 3 there is support for automatic connection pools so you don t have to manually handle connections and publishers to reuse connections The connection pool is enabled by default since version 2 5 See the BROKER_POOL_LIMIT setting for more information You can handle the connection manually by creating a publisher numbers 2 2 4 4 8 8 16 16 results publisher add get_publisher try for args in numbers res add apply_async args args publisher publisher results append res finally publisher close publisher connection close print res get for res in results Note This particular example is better expressed as a task set See Task Sets Tasksets already reuses connections The connection timeout is the number of seconds to wait before giving up on establishing the connection You can set this by using the connect_timeout argument to apply_async add apply_async 10 10 connect_timeout 3 Or if you handle the connection manually publisher add get_publisher connec
180. art 348 Chapter 13 Internals Celery Documeniation Release 2 5 5 BasePool rlimit_safe True set to true if pool supports rate limits this is here for gevent which currently does not implement the necessary timers BasePool signal_safe True set to true if the pool can be shutdown from within a signal handler BasePool start BasePool stop BasePool terminate BasePool terminate_Job pid celery concurrency base apply_target target args kwargs callback None ac cept_callback None pid None _ 13 6 19 celery concurrency threads minefield class celery concurrency threads NullDict dict None kwargs class celery concurrency threads TaskPool args kwargs on_apply target args None kwargs None callback None accept_callback None _ on_start on_stop 13 6 20 celery beat e celery beat j celery beat The Celery periodic task scheduler copyright 3 2009 2012 by Ask Solem license BSD see LICENSE for more details celery beat EmbeddedService args kwargs Return embedded clock service Parameters thread Run threaded instead of as a separate process Default is False class celery beat PersistentScheduler args kwargs close get_schedule info persistence lt module shelve from usr lib python2 7 shelve pyc gt 13 6 Internal Module Reference 349 Celery Documentation Release 2 5 5 setup_sched
181. as been replaced by a single setting CELERY_RESULT_DBURI The value here should be an SQLAIchemy Connection String some examples include j qlite filename CELERY_RESULT_DBURI sqlite celerydb sqlite CELERY_RESULT_DBURI mysql scott tiger localhost foo CELERY_RESULT_DBURI postgresql scott tiger localhost mydatabase CELERY_RESULT_DBURI oracle scott tiger 127 0 0 1 1521 sidname See SQLAIchemy Connection Strings for more information about connection strings To specify additional SQLAIchemy database engine options you can use the CELERY_RESULT_ENGINE_OPTIONS setting CELERY_RESULT_ENGINE_OPTIONS echo True Cache result backend The cache result backend is no longer using the Django cache framework but it supports mostly the same configuration syntax 212 Chapter 11 Change history Celery Documeniation Release 2 5 5 CE H RY_CACHE_BACKEND memcached A example com 11211 B example com To use the cache backend you must either have the pylibmc or python memcached library installed of which the former is regarded as the best choice The support backend types are memcached and memory we haven t felt the need to support any of the other backends provided by Django 11 34 4 Backward incompatible changes e Default python loader now pr
182. as messages The model is normal django stuff nothing new there But now we get on to the messaging It has been a tradition for me to put the projects messaging related code in its own messaging py module and I will continue to do so here so maybe you can adopt this practice In this module we have two functions e send_increment_clicks This function sends a simple message to the broker The message body only contains the URL we want to increment as plain text so the exchange and routing key play a role here We use an exchange called clicks with a routing key of increment_click so any consumer binding a queue to this exchange using this routing key will receive these messages e process_clicks This function processes all currently gathered clicks sent using send_increment_clicks Instead of issuing one database query for every click it processes all of the messages first calculates the new click count and issues one update per URL A message that has been received will not be deleted from the broker until it has been acknowledged by the receiver so if the receiver dies in the middle of processing the message it will be re sent at a later point in time This guarantees delivery and we respect this feature here by not acknowledging the message until the clicks has actually been written to disk Note This could probably be optimized further with some hand written SQL but it will do for now Let s say it s an exercise left for the
183. ask wait for the task to finish or get its return value or if the task failed the exception and traceback By default django celery stores this state in the Django database you may consider choosing an alternate result back end or disabling states alltogether see Result Backends To demonstrate how the results work we can execute the task again but this time keep the result instance returned gt gt gt result add delay 4 4 gt gt gt result ready returns True if the task has finished processing False gt gt gt result result task is not ready so no return value None gt gt gt result get Waits until the task is done and returns the retval gt gt gt result result direct access to result doesn t re raise errors gt gt gt result successful returns True if the task didn t end in failure True If the task raises an exception the return value of result successful willbe False and result result will contain the exception instance raised by the task 4 1 5 Where to go from here To learn more you should read the Celery User Guide and the Celery Documentation in general 4 2 Unit Testing 4 2 1 Testing with Django The first problem you ll run in to when trying to write a test that runs a task is that Django s test runner doesn t use the same database as your celery daemon is using If you re using the database backend this means that your tombstones won t show up in your
184. ask http Task webhooks implementation copyright 3 2009 2012 by Ask Solem license BSD see LICENSE for more details class celery task http HttpDispatch url method task_kwargs logger Make task HTTP request and collect the task result Parameters e url The URL to request method HTTP method used Currently supported methods are GET and POST e task_kwargs Task keyword arguments e logger Logger used for user system feedback dispatch Dispatch callback and return result http_headers make_request url method params Makes an HTTP request and returns the response timeout 5 user_agent celery 2 5 5 class celery task http HttpDispatchTask Task dispatching to an URL Parameters url The URL location of the HTTP callback task 276 Chapter 12 API Reference Celery Documeniation Release 2 5 5 e method Method to use when dispatching the callback Usually GET or POST e kwargs Keyword arguments to pass on to the HTTP callback url If this is set this is used as the default URL for requests Default is to require the user of the task to supply the url as an argument as this attribute is intended for subclasses method If this is set this is the default method used for requests Default is to require the user of the task to supply the method as an argument as this attribute is intended for subclasses method None name celery task http Htt
185. askPool is_green True askPool num_processes askPool on_apply target args None kwargs None callback None accept_callback None kE askPool on_start 346 Chapter 13 Internals Celery Documeniation Release 2 5 5 TaskPool on_stop TaskPool rlimit_safe False TaskPool shrink n TaskPool signal_safe False class celery concurrency gevent Timer schedule None on_error None on_tick None kwargs class Schedule args kwargs clear enter entry eta None priority 0 queue Timer ensure_started Timer start Timer stop 13 6 18 celery concurrency base class celery concurrency base BasePool limit None putlocks True logger None options CLOSE 2 RUN 1 TERMINATE 3 class Timer schedule None on_error None on_tick None kwargs class Entry fun args None kwargs None cancel cancelled False class BasePool Timer Schedule max_interval 2 on_error None ETA scheduler clear empty Is the schedule empty enter entry eta None priority 0 Enter function into the scheduler Parameters e entry Item to enter e eta Scheduled time as a datet ime datetime object e priority Unused handle_error exc_info 13 6 Internal Module Reference 347 Celery Documentation Release 2 5 5 Base Base Base Base Base Base Base Base Base Base Base Base Base Base Base
186. askSet failed result was incorrect See issue 132 e Now creates different loggers per task class See issue 129 e Missing queue definitions are now created automatically You can disable this using the CELERY_CREATE_MISSING_QUEUES setting The missing queues are created with the following options CELERY_QUEUES name exchange name exchange_type direct routing_key name This feature is added for easily setting up routing using the Q option to celeryd celeryd Q video image See the new routing section of the User Guide for more information Routing Tasks e New Task option Task queue If set message options will be taken from the corresponding entry in CELERY_QUEUES exchange exchange_type and routing_key will be ignored e Added support for task soft and hard time limits New settings added CELERYD_TASK_TIME_ LIMIT Hard time limit The worker processing the task will be killed and replaced with a new one when this is exceeded CELERYD_SOFT_TASK_TIME_LIMIT Soft time limit The celery exceptions SoftTimeLimitExceeded excep tion will be raised when this is exceeded The task can catch this to e g clean up before the hard time limit comes New command line arguments to celeryd added time limit and soft time limit What s left This won t work on pl
187. at the same time so rather than using a fixed port the debugger will search for an available port starting from the base port 6900 by default The base port can be changed using the environment variable envvar CELERY RDB PORT By default the debugger will only be available from the local host 11 25 2 2 0 191 Celery Documentation Release 2 5 5 to enable access from the outside you have to set th nvironment variable envvar CELERY_RDB_HOST When celeryd encounters your breakpoint it will log the following information INFO MainProcess Got task from broker tasks add d7261c71 4962 47e5 b342 244 8bedd20e8 WARNING PoolWorker 1 Remote Debugger 6900 Please telnet 127 0 0 1 6900 Type exit in session to continue 2011 01 18 14 25 44 119 WARNING PoolWorker 1 Remote Debugger 6900 Waiting for client If you telnet the port specified you will be presented with a pdb shell telnet localhost 6900 Connected to localhost Escape character is gt opt devel demoapp tasks py 128 add gt return result Pdb Enter help to get a list of available commands It may be a good idea to read the Python Debugger Manual _ if you have never used pdb before e Events are now transient and is using a topic exchange instead of direct The CELERYD_EVENT_EXCHANGE CELERYD_EVENT_ROUTING_KEY CEL ERYD_EVENT_EXCHAN
188. atforms not supporting signals and specifically the SIGUSR signal yet So an alternative the ability to disable the feature all together on nonconforming platforms must be implemented Also when the hard time limit is exceeded the task result should be a TimeLimitExceeded exception e Test suite is now passing without a running broker using the carrot in memory backend 216 Chapter 11 Change history Celery Documeniation Release 2 5 5 e Log output is now available in colors Log level Color DEBUG Blue WARNING Yellow CRITICAL Magenta ERROR Red This is only enabled when the log output is a tty You can explicitly enable disable this feature using the CELERYD_LOG_COLOR setting e Added support for task router classes like the django multi db routers New setting CELERY_ROUTES This is a single or a list of routers to traverse when sending tasks Dictionaries in this list converts to acelery routes MapRoute instance Examples gt gt gt CELERY_ROUT Fl n 1 celery ping default s add cpu bound C a w H Q D D a a D gt gt gt CELERY_ROUT ea n 1 myapp tasks Router celery ping default Where myapp tasks Router could be class Router def route_for_task task args kKwargs Dies if task celery ping return default route_for_task may return a string or a di
189. ave to type update_twitter_status retry here which can be annoying for long task names Note This will not work if the task function is called directly i e update_twitter_status a b For that to work apply must be used update_twitter_status apply a b 10 4 6 In Other News e Now depends on Kombu 2 1 0 e Efficient Chord support for the memcached backend Issue 533 This means memcached joins Redis in the ability to do non polling chords Contributed by Dan McGee e Adds Chord support for the AMQP backend The AMQP backend can now use the fallback chord solution e Sending QUIT to celeryd will now cause it cold terminate That is it will not finish executing the tasks it is currently working on Contributed by Alec Clowes e New detailed mode for the Cassandra backend Allows to have a detailed mode for the Cassandra backend Basically the idea is to keep all states using Cassandra wide columns New states are then appended to the row as new columns the last state being the last column See the CASSANDRA_D ETAIL ED_MOD E setting 10 4 News 165 Celery Documentation Release 2 5 5 Contributed by Steeve Morin The crontab parser now matches Vixie Cron behavior when parsing ranges with steps e g 1 59 2 Contributed by Daniel Hepper celerybeat can now be configured on the command line like celeryd Additional configuration must be added at the end of the a
190. bjects from celery import celery from models import CeleryStats celery task def write_stats_to_db stats celery control inspect stats timeout 1 for node_name reply in stats CeleryStats objects update_stat node_name stats In the example above the actual application instance is imported from a module in the project this module could look something like this from celery import Celery celery Celery celery config_from_object BROKER_URL amqp 13 1 4 Module Overview e celery app This is the core of Celery the entry point for all functionality e celery loaders Every app must have a loader The loader decides how configuration is read what happens when the worker starts when a task starts and ends and so on 314 Chapter 13 Internals Celery Documeniation Release 2 5 5 The loaders included are app Custom celery app instances uses this loader by default default single mode uses this loader by default Extension loaders also exist like django celery celery pylons and so on celery worker This is the worker implementation celery backends Task result backends live here celery apps Major user applications celeryd and celerybeat celery bin Command line applications setup py creates setuptools entrypoints for these celery concurrency Execution pool implementations processes eventlet gevent threads celery db Database models for the SQLAlIchemy
191. ble to detect if the system has been compromised Logs Logs are usually the first place to look for evidence of security breaches but they are useless if they can be tampered with A good solution is to set up centralized logging with a dedicated logging server Acess to it should be restricted In addition to having all of the logs in a single place if configured correctly it can make it harder for intruders to tamper with your logs This should be fairly easy to setup using syslog see also syslog ng and rsyslog Celery uses the Logging library and already has support for using syslog A tip for the paranoid is to send logs using UDP and cut the transmit part of the logging servers network cable Tripwire Tripwire is a now commercial data integrity tool with several open source implementations used to keep crypto graphic hashes of files in the file system so that administrators can be alerted when they change This way when the damage is done and your system has been compromised you can tell exactly what files intruders have changed password files logs backdoors rootkits and so on Often this is the only way you will be able to detect an intrusion Some open source implementations include e OSSEC 2 10 Security 77 Celery Documeniation Release 2 5 5 e Samhain e Open Source Tripwire e AIDE Also the ZFS file system comes with built in integrity checks that can be used 2 11 Optimizing 2 11 1 Intr
192. c previously did Like converting countdowns to eta so celery execute apply_async is now simply a convenient front end to celery messaging TaskPublisher send_task using the task classes default options Also celery execute send_task has been introduced which can apply tasks using just the task name useful if the client does not have the destination task in its task registry Example 226 Chapter 11 Change history Celery Documeniation Release 2 5 5 gt gt gt from celery execute import send_task gt gt gt result send_task celery ping args kwargs gt gt gt result get e camqadm This is a new utility for command line access to the AMQP API Excellent for deleting queues bindings exchanges experimentation and testing camqadm 1 gt help Gives an interactive shell type help for a list of commands When using Django use the management command instead python manage py camqadm 1 gt help e Redis result backend To conform to recent Redis API changes the following settings has been deprecated REDIS_TIMEOUT REDIS_CONNECT_RETRY These will emit a DeprecationWarning if used A REDIS_PASSWORD setting has been added so you can use the new simple authentication mech anism in Redis e The redis result backend no longer calls SAVE when disconnecting as this is apparently better handled by Redis itself e If settings DEBUG is on celeryd now warns about the possib
193. celery execute send_task You can also execute a task by name from any language that has an AMQP client gt gt gt from celery execute import send_task gt gt gt send_task tasks add args 2 2 kwargs lt AsyncResult 373550e8 b9a0 4666 bc61 ace0lfa4f9ld gt 156 Chapter 9 Frequently Asked Questions Celery Documeniation Release 2 5 5 9 7 5 How can I get the task id of the current task Answer The current id and more is available in the task request task def mytask cache set mytask request id Running For more information see Context 9 7 6 Can I specify a custom task_id Answer Yes Use the task_id argument to Task apply_async gt gt gt task apply_async args kwargs task_id 9 7 7 Can I use decorators with tasks Answer Yes But please see note at Decorating tasks 9 7 8 Can I use natural task ids Answer Yes but make sure it is unique as the behavior for two tasks existing with the same id is undefined The world will probably not explode but at the worst they can overwrite each others results 9 7 9 How can I run a task once another task has finished Answer You can safely launch a task inside a task Also a common pattern is to use callback tasks task def add x y callback None result x y if callback subtask callback delay result return result task ignore_result True def log_result result kwargs logger log_result g
194. ception or has exceeded the retry limit The result attribute then contains the exception raised by the task SUCCESS The task executed successfully The result attribute then contains the tasks return value AsyncResult status The tasks current state Possible values includes PENDING The task is waiting for execution STARTED The task has been started RETRY The task is to be retried possibly because of failure FAILURE The task raised an exception or has exceeded the retry limit The result attribute then contains the exception raised by the task SUCCESS The task executed successfully The result attribute then contains the tasks return value 12 9 celery result 269 Celery Documentation Release 2 5 5 AsyncResult successful Returns True if the task executed successfully AsyncResult task_id None The task uuid AsyncResult traceback Get the traceback of a failed task AsyncResult wait timeout None propagate True interval 0 5 Wait until task is ready and return its result Warning Waiting for tasks within a task may lead to deadlocks Please read Avoid launching syn chronous subtasks Parameters e timeout How long to wait in seconds before the operation times out e propagate Re raise exception if the task failed e interval Time to wait in seconds before retrying to retrieve the result Note that this does not have any effect when using the AMQP result
195. change already exists e durable Durable exchanges are persistent That is they survive a broker restart e auto_delete This means the queue will be deleted by the broker when there are no more queues using it queue declare queue_name passive durable exclusive auto_delete Declares a queue by name Exclusive queues can only be consumed from by the current connection Exclusive also implies auto_delete queue bind queue_name exchange_name routing_key Binds a queue to an exchange with a routing key Unbound queues will not receive messages so this is necessary queue delete name if_unused False if_empty False Deletes a queue and its binding exchange delete name if_unused False Deletes an exchange Note Declaring does not necessarily mean create When you declare you assert that the entity exists and that it s operable There is no rule as to whom should initially create the exchange queue binding whether consumer or producer Usually the first one to need it will be the one to create it Hands on with the API Celery comes with a tool called camqadm short for Celery AMQ Admin It s used for command line access to the AMQP API enabling access to administration tasks like creating deleting queues and exchanges purging queues or sending messages You can write commands directly in the arguments to camqadm or just start with no arguments to start it in shell mode camqadm
196. change how you run your code not how you write it e It uses epoll 4 or libevent for highly scalable non blocking I O 2 12 Concurrency 79 Celery Documeniation Release 2 5 5 e Coroutines ensure that the developer uses a blocking style of programming that is similar to threading but provide the benefits of non blocking I O e The event dispatch is implicit which means you can easily use Eventlet from the Python interpreter or as a small part of a larger application Celery supports Eventlet as an alternative execution pool implementation It is in some cases superior to multiprocess ing but you need to ensure your tasks do not perform blocking calls as this will halt all other operations in the worker until the blocking call returns The multiprocessing pool can take use of multiple processes but how many is often limited to a few processes per CPU With Eventlet you can efficiently spawn hundreds or thousands of green threads In an informal test with a feed hub system the Eventlet pool could fetch and process hundreds of feeds every second while the multiprocessing pool spent 14 seconds processing 100 feeds Note that is one of the applications evented I O is especially good at asynchronous HTTP requests You may want a mix of both Eventlet and multiprocessing workers and route tasks according to compatibility or what works best Enabling Eventlet You can enable the Eventlet pool by using the P option to celeryd
197. change to use when no custom exchange is specified The default is celery CELERY_DEFAULT_EXCHANGE_TYPE Default exchange type used when no custom exchange is specified The default is direct CELERY_DEFAULT_ROUTING_KEY The default routing key used when sending tasks The default is celery CELERY_DEFAULT_DELIVERY_MODE Can be transient or persistent The default is to send persistent messages 3 2 14 Broker Settings BROKER_TRANSPORT Aliases BROKER_BACKEND Deprecated aliases CARROT_BACKEND The Kombu transport to use Default is anqplib You can use a custom transport class name or select one of the built in transports amqplib pika redis beanstalk sqlalchemy django mongodb couchdb 3 2 Configuration Directives 95 Celery Documeniation Release 2 5 5 BROKER_URL Default broker URL This must be an URL in the form of transport userid password hostname port virtual_host Only the scheme part transport is required the rest is optional and defaults to the specific transports default values If this setting is defined it will override a subset of the other BROKER options These options are BROKER_HOST BROKER_USER BROKER_PASSWORD BROKER_PORT and BROKER_VHOST See the Kombu documentation for more information about broker URLs BROKER_HOST Hostname of the broker BROKER_PORT Custom port of the broker Default is to use the default port for the select
198. changes in modules and fires reload commands Monitor alias of StatMonitor body on_change files stop class celery worker autoreload BaseMonitor files on_change None shutdown_event None interval 0 5 on_change modified start stop 338 Chapter 13 Internals Celery Documeniation Release 2 5 5 class celery worker autoreload InotifyMonitor modules on_change None kwargs File change monitor based on Linux kernel inotify subsystem on_change modified process_ event process_IN_ ATTRIB event process_IN_ MODIFY event start stop class celery worker autoreload KQueueMonitor args kwargs File change monitor based on BSD kernel event notifications start stop celery worker autoreload Monitor alias of StatMonitor class celery worker autoreload StatMonitor files on_change None shutdown_event None interval 0 5 File change monitor based on the stat system call start class celery worker autoreload WorkerComponent w autoreload None kwargs create w name autoreloader namespace worker requires pool celery worker autoreload default_implementation celery worker autoreload file_hash filename algorithm md5 13 6 11 celery worker autoscale e celery worker autoscale j celery worker autoscale This module implements the internal thread responsible for growing and shrinking the pool accor
199. chedule The extension db will be appended to the filename scheduler Scheduler class to use Default is celery beat PersistentScheduler logfile Path to log file If no logfile is specified stderr is used loglevel Logging level choose between DEBUG INFO WARNING ERROR CRITICAL or FATAL class celery bin celerybeat BeatCommand app None get_app None enable_config_from_cmdline True get_options preload_options lt Option at 0x5c213f8 app gt lt Option at Ox5acf950 b broker gt lt Option at 0x5acf998 loade1 prepare_preload_options options run detach False logfile None pidfile None uid None gid None umask None work ing_directory None kwargs supports_args False celery bin celerybeat main 12 35 celery bin celeryev class celery bin celeryev EvCommand app None get_app None get_options preload_options lt Option at 0x5c213f8 app gt lt Option at Ox5acf950 b broker gt lt Option at 0x5acf998 loade1 12 34 celery bin celerybeat 301 Celery Documentation Release 2 5 5 prepare_preload_options options run dump False camera None frequency 1 0 maxrate None loglevel INFO log file None prog_name celeryev pidfile None uid None gid None umask None work ing_directory None detach False kwargs run_evcam camera logfile None pidfile None uid None gid None umask None work ing_directory None detach Fals
200. chords Chords task set callbacks copyright 3 2009 2012 by Ask Solem license BSD see LICENSE for more details class celery task chords Chord accept_magic_kwargs False name celery chord run set body interval 1 max_retries None propagate False kwargs class celery task chords chord tasks options class Chord accept_magic_kwargs False name celery chord run set body interval 1 max_retries None propagate False kwargs 12 8 celery task chords 267 Celery Documentation Release 2 5 5 12 9 celery result e celery result j 12 9 1 celery result Task results state and groups of results copyright 3 2009 2012 by Ask Solem license BSD see LICENSE for more details class celery result AsyncResult task_id backend None task_name None app None Query task state Parameters e task_id see task_id e backend see backend exception TimeoutError Error raised for timeouts AsyncResult backend None The task result backend to use AsyncResult failed Returns True if the task failed AsyncResult forget Forget about and possibly remove the result of this task AsyncResult get timeout None propagate True interval 0 5 Wait until task is ready and return its result Warning Waiting for tasks within a task may lead to deadlocks Please read Avoid launching syn chronous subtasks Parameters e timeout How
201. class celery utils timer2 Schedule max_interval 2 on_error None ETA scheduler clear empty Is the schedule empty enter entry eta None priority 0 Enter function into the scheduler Parameters e entry Item to enter e eta Scheduled time as a datet ime datetime object e priority Unused handle_error exc_info info on_error None queue exception celery utils timer2 TimedFunctionFailed class celery utils timer2 Timer schedule None on_error None on_tick None kwargs class Entry fun args None kwargs None cancel cancelled False 13 6 Internal Module Reference 385 Celery Documentation Release 2 5 5 class Timer Schedule max_interval 2 on_error None ETA scheduler clear empty Is the schedule empty enter entry eta None priority 0 Enter function into the scheduler Parameters e entry Item to enter e eta Scheduled time as a datet ime datetime object e priority Unused handle_error exc_info info on_error None queue Timer apply_ after msecs fun args kwargs priority 0 Timer apply_at eta fun args kwargs priority 0 Timer apply entry entry Timer apply_ interval msecs fun args kwargs priority 0 Timer cancel tref Timer clear Timer empty Timer ensure_started Timer enter entry eta priority None Timer enter_after msecs entry priority 0 Timer exit_after msecs prior
202. coding e celery utils encoding I Utilities to encode text and to safely emit text from running applications without crashing with the infamous UnicodeDecode ce ce ce ce ce ce ce ce copyright 3 2009 2012 by Ask Solem license BSD see LICENSE for more details lery lery lery lery lery lery lery lery u u u tils tils tils tils tils tils tils tils encodi encodi encodi encodi encodi encodi encodi encodi Error exception bytes_to_str s default_encode obj default_encoding ensure_bytes s from_ut 8 s args kwargs safe_repr o errors replace safe_str s errors replace Str_to_bytes s 13 6 49 celery utils compat e celery utils compat j 382 Chapter 13 Internals Celery Documeniation Release 2 5 5 celery utils compat Backward compatible implementations of features only available in newer Python versions copyright 3 2009 2012 by Ask Solem license BSD see LICENSE for more details celery utils compat chain_from_iterable chain from_iterable iterable gt chain object Alternate chain contructor taking a single iterable argument that evaluates lazily 13 6 50 celery utils patch e celery utils patch j celery utils patch Monkey patch to ensure loggers are process aware copyright 3 2009 2012 by Ask Solem license BSD see LICENSE fo
203. collection name to store task meta data Defaults to celery_taskmeta Example configuration Q iiri iERY_RESULT_BACKEND mongodb ERY_MONGODB_BACKEND_SETTINGS hosts 102 166 1100 pores 30000 database mydb taskmeta_collection my_taskmeta_collection Q Hi 3 2 12 Cassandra backend settings Note The Cassandra backend requires the pycassa library http pypi python org pypi pycassa To install the pycassa package use pip or easy_install pip install pycassa This backend requires the following configuration directives to be set 3 2 Configuration Directives 93 Celery Documentation Release 2 5 5 CASSANDRA_SERVERS List of host port Cassandra servers e g localhost 9160 CASSANDRA_KEYSPACE The keyspace in which to store the results e g tasks_keyspace CASSANDRA_COLUMN_FAMILY The column family in which to store the results eg tasks CASSANDRA_READ_CONSISTENCY The read consistency used Values can be ONE QUORUM or ALL CASSANDRA_WRITE_CONSISTENCY The write consistency used Values can be ONE QUORUM or ALL CASSANDRA_DETAILED_MODE Enable or disable detailed mode Default is False This mode allows to use the power of Cassandra wide columns to store all states for a task as a wide column instead of only the last one To use this mode you need to configure your ColumnFamily to use the T
204. configure these settings CELERY_RESULT_BACKEND redis CELERY_REDIS_HOST localhost ic G ELERY_REDIS_PORT 63 79 ELERY_REDIS_DB 0 For a complete list of options supported by the Redis result backend see Redis backend settings 1 2 3 Using SQLAlchemy Installation Configuration Celery needs to know the location of your database which should be the usual SQLAIchemy connection string but with sqla prepended to it BROKER_URL sqlatsqlite celerydb sqlite This transport uses only the BROKER_URL setting which have to be an SQLAIchemy database URI Please see SQLAIchemy Supported Databases for a table of supported databases Here s a list of examples using a selection of other SQLAIchemy Connection String s sqlite filename BROKER_URL sqlatsqlite celerydb sqlite 1 sqlatmysql scott tiger localhost foo nostaqresa 7 I g SOL BROKER_URL sqlat postgresql scott tiger localhost mydatabase 1 2 Brokers 9 Celery Documentation Release 2 5 5 BROKER_URL sqlatoracle scott tiger 127 0 0 1 1521 sidname Results To store results in the database as well you should configure the result backend See Database backend settings Limitations The SQLAIchemy database transport does not currently support e Remote control commands celeryev broadcast e Events including the Django Admin monitor e Using more
205. ct A string then means it s a queue name in CELERY_QUEUES a dict means it s a custom route When sending tasks the routers are consulted in order The first router that doesn t return None is the route to use The message options is then merged with the found route settings where the routers settings have priority Example if apply_async has these arguments gt gt gt Task apply_async immediate se exchange video routing_key video compress and a router returns immediate exchange urgent the final message options will be immediate exchange urgent routing_key video compress and any default message options defined in the Task class e New Task handler called after the task returns after_return 11 34 2 0 0 217 Celery Documentation Release 2 5 5 e ExceptionInfo now passed to on_retry on_failure as einfo keyword argument e celeryd Added CELERYD_MAX_TASKS_PER_CHILD maxtasksperchild Defines the maximum number of tasks a pool worker can process before the process is terminated and replaced by a new one e Revoked tasks now marked with state REVOKED and result get will now raise TaskRevokedError e celery task control ping now works as expected e apply throw True CELERY_EAGER_PROPAGATES_EXCEPTIONS Makes eager execution re raise task errors e New signal celery
206. ction There are several tools available to monitor and inspect Celery clusters This document describes some of these as as well as features related to monitoring like events and broadcast com mands 2 9 2 Workers celeryctl Management Utility New in version 2 1 celeryctl is a command line utility to inspect and manage worker nodes and to some degree tasks To list all the commands available do celeryctl help or to get help for a specific command do celeryctl lt command gt help Commands shell Drop into a Python shell The locals will include the celery variable which is the current app Also all known tasks will be automati cally added to locals unless the without tasks flag is set Uses Ipython bpython or regular python in that order if installed You can force an implementation using force ipython I force bpython B or force python P status List active nodes in this cluster celeryctl status result Show the result of a task celeryctl result t tasks add 4e196aa4 0141 4601 8138 7aa33db0f 577 Note that you can omit the name of the task as long as the task doesn t use a custom result backend purge Purge messages from all configured task queues celeryctl purge Warning There is no undo for this operation and messages will be permanently deleted inspect active List active tasks celeryctl inspect active These are all the tasks that are current
207. cumeniation Release 2 5 5 task def expand_abbreviations article_id article Article objects get id article_id article body replace MyCorp My Corporation article save gt gt gt expand_abbreviations article_id There might even be performance benefits to this approach as sending large messages may be expensive Database transactions Let s have a look at another example from django db import transaction transaction commit_on_success def create_article request article Article objects create expand_abbreviations delay article pk This is a Django view creating an article object in the database then passing the primary key to a task It uses the commit_on_success decorator which will commit the transaction when the view returns or roll back if the view raises an exception There is a race condition if the task starts executing before the transaction has been committed The database object does not exist yet The solution is to always commit transactions before sending tasks depending on state from the current transaction transaction commit_manually def create_article request try article Article objects create except transaction rollback raise else transaction commit expand_abbreviations delay article pk 2 2 13 Example Let s take a real wold example A blog where comments posted needs to be filtered for spam When the comment is created the spam f
208. curity concern as this can indeed be a real issue It is essential that you protect against unauthorized access to your broker databases and other services transmitting pickled data 154 Chapter 9 Frequently Asked Questions Celery Documeniation Release 2 5 5 For the task messages you can set the CELERY_TASK_SERIALIZER setting to json or yaml instead of pickle There is currently no alternative solution for task results but writing a custom result backend using JSON is a simple task Note that this is not just something you should be aware of with Celery for example also Django uses pickle for its cache client 9 5 2 Can messages be encrypted Answer Some AMQP brokers supports using SSL including RabbitMQ You can enable this using the BROKER_USE_SSL setting It is also possible to add additional encryption and security to messages if you have a need for this then you should contact the Mailing list 9 5 3 Is it safe to run celeryd as root Answer No We re not currently aware of any security issues but it would be incredibly naive to assume that they don t exist so running the Celery services celeryd celerybeat celeryev etc as an unprivileged user is recommended 9 6 Brokers 9 6 1 Why is RabbitMQ crashing Answer RabbitMQ will crash if it runs out of memory This will be fixed in a future release of RabbitMQ please refer to the RabbitMQ FAQ http www rabbit
209. d If the message body can t be decoded it is now passed through safe_st r when logging This to ensure we don t get additional decoding errors when trying to log the failure app config_from_object app config_from_envvar now works for all loaders Now emits a user friendly error message if the result backend name is unknown Issue 349 celery contrib batches Now sets loglevel and logfile in the task request so task get_logger works with batch tasks Issue 357 celeryd An exception was raised if using the amqp transport and the prefetch count value exceeded 65535 Issue 359 The prefetch count is incremented for every received task with an ETA countdown defined The prefetch count is a short so can only support a maximum value of 65535 If the value exceeds the maximum value we now disable the prefetch count it is re enabled as soon as the value is below the limit again cursesmon Fixed unbound local error Issue 303 eventlet gevent is now imported on demand so autodoc can import the modules without having eventlet gevent installed celeryd Ack callback now properly handles Att ributeError Task after_return is now always called after the result has been written Cassandra Result Backend Should now work with the latest pycassa version 186 Chapter 11 Change history Celery Documeniation Release 2 5 5 multiprocessing Pool No longer cares if the putlock semaphore is released too many times this can hap
210. d and scheduled for removal in v2 0 e TaskSet run has been renamed to TaskSet apply_async TaskSet run has now been deprecated and is scheduled for removal in v2 0 41 3 News e Rate limiting support per task type or globally New periodic task system Automatic registration New cool task decorator syntax celeryd now sends events if enabled with the E argument Excellent for monitoring tools one is already in the making http github com celery celerymon Current events include worker heartbeat task received succeeded failed retried worker online worker offline You can now delete revoke tasks that has already been applied You can now set the hostname celeryd identifies as using the hostname argument Cache backend now respects the CELERY_TASK_RESULT_EXPIRES setting Message format has been standardized and now uses ISO 8601 format for dates instead of datetime celeryd now responds to the SIGHUP signal by restarting itself Periodic tasks are now scheduled on the clock 230 Chapter 11 Change history Celery Documeniation Release 2 5 5 Le timedelta hours 1 means every hour at 00 minutes not every hour from the server starts To revert to the previous behaviour you can set PeriodicTask relative True e Now supports passing execute options to a TaskSets list of args e g gt gt gt ts TaskSet add 2 2 countdown 1 4 4 countd
211. d that the bucket will be refilled e capacity Maximum number of tokens in the bucket Default is 1 exception RateLimitExceeded Tok Tok Tok Tok Tok Tok The token buckets rate limit has been exceeded nBucketQueue clear Delete all data in the queue nBucketQueue empty Returns True if the queue is empty nBucket Queue expected_time tokens 1 Returns the expected time in seconds of when a new token should be available nBucket Queue get block True Remove and return an item from the queue Raises e RateLimitExceeded If a token could not be consumed from the token bucket consuming from the queue too fast e Queue Empty If an item is not immediately available nBucket Queue get_nowait Remove and return an item from the queue without blocking Raises e RateLimitExceeded If a token could not be consumed from the token bucket consuming from the queue too fast e Queue Empty If an item is not immediately available nBucket Queue items Underlying data Do not modify nBucket Queue put item block True Put an item onto the queue nBucket Queue put_nowait item Put an item into the queue without blocking Raises Queue Full If a free slot is not immediately available nBucket Queue qsize Returns the size of the queue nBucketQueue wait block False Wait until a token can be retrieved from the bucket and return the next item
212. database result backend should be moved into celery backends database celery events Sending and consuming monitoring events also includes curses monitor event dumper and utilities to work with in memory cluster state celery execute trace How tasks are executed and traced by the worker and in eager mode celery security Security related functionality currently a serializer using cryptographic digests celery task single mode interface to creating tasks and controlling workers celery tests The unittest suite celery utils Utility functions used by the celery code base Much of it is there to be compatible across Python versions celery contrib Additional public code that doesn t fit into any other namespace 13 1 Contributors Guide to the Code 315 Celery Documentation Release 2 5 5 13 2 Celery Deprecation Timeline e Removals for version 2 0 13 2 1 Removals for version 2 0 The following settings will be removed Setting name Replace with CELERY_AMOP_CONSUMER_QUEUES CELERY_AMOP_CONSUMER_QUEUES CELERY_QUEUES CELERY_QUEUES CELERY_DEFAULT_EXCHANGE CEL ERY_DEFAULT_AMQP_EXCHANGE_TYPE CELERY_AMQP_EXCHANGE CELERY_AMQP_EXCHANGE_TYPE CEL CELERY_QUEUES ERY_AMQP_CONSUMER_ROUTING_KEY CEL CELERY_DEFAULT_ROUTING_KEY ERY_AMQP_PUBLISHER_ROUTING_KEY e CELERY_LOADER definitions without class name E g celery loaders default needs to include th
213. dicated in the source code But you are encouraged to use the more flexible C ELERYBEAT_SCHEDULE setting e Built in daemonization support of celeryd using celeryd multi is no longer experimental and is considered pro duction quality See Generic init scripts if you want to use the new generic init scripts e Added support for message compression using the CE ERY_MESSAGE_COMPRESSION setting or the com pression argument to apply_async This can also be set using routers e celeryd Now logs stacktrace of all threads when receiving the S GUSR signal Does not work on cPython 2 4 Windows or Jython Inspired by https gist github com 737056 e Can now remotely terminate kill the worker process currently processing a task The revoke remote control command now supports a terminate argument Default signal is TERM but can be specified using the signal argument Signal can be the uppercase name of any signal defined in the signal module in the Python Standard Library Terminating a task also revokes it Example gt gt gt from celery task control import revoke gt gt gt revoke task_id terminate gt gt gt revoke task_id terminate gt gt gt revoke task_id terminate signal KILL signal SIGKILL e TaskSetResult join_native Backend optimized version of join If available this version uses the backends ability to retrieve multiple results at o
214. ding to the current autoscale settings The autoscale thread is only enabled if autoscale has been enabled on the command line copyright 3 2009 2012 by Ask Solem license BSD see LICENSE for more details 13 6 Internal Module Reference 339 Celery Documentation Release 2 5 5 class celery worker autoscale Autoscaler pool max_concurrency min_concurrency 0 keepalive 30 logger None body force_scale_down n force_scale_up n info processes qty scale scale_down n scale_up n update max None min None class celery worker autoscale WorkerComponent w kwargs create w name autoscaler namespace worker requires pool 13 6 12 celery concurrency celery concurrency get_implementation c s 13 6 13 celery concurrency solo class celery concurrency solo TaskPool args kwargs Solo task pool blocking inline fast 13 6 14 celery concurrency processes class celery concurrency processes TaskPool limit None putlocks True _logger None options Multiprocessing Pool implementation class Pool processes None initializer None initargs maxtasksperchild None timeout None soft_timeout None force_execv False Class which supports an async version of the apply builtin class Process args kwargs class TaskPool Pool ResultHandler outqueue get cache poll join_exited_workers putlock body 340 Chapter 13 Internals
215. e Module name celery equivalent billiard pool billiard serialization billiard utils functional celery concurrency processes pool celery serialization celery utils functional The billiard distribution may be maintained depending on interest now depends on carrot gt 0 10 5 now depends on pyparsing celeryd Added purge as an alias to discard celeryd Ctrl C SIGINT once does warm shutdown hitting Ctrl C twice forces termination Added support for using complex crontab expressions in periodic tasks For example you can now use gt gt gt crontab minute 15 or even gt gt gt crontab minute 30 hour 8 17 1 2 day_of_week thu fri See Periodic Tasks celeryd Now waits for available pool processes before applying new tasks to the pool This means it doesn t have to wait for dozens of tasks to finish at shutdown because it has applied prefetched tasks without having any pool processes available to immediately accept them See issue 122 11 34 2 0 0 215 Celery Documentation Release 2 5 5 e New built in way to do task callbacks using subtask See Sets of tasks Subtasks and Callbacks for more information e TaskSets can now contain several types of tasks TaskSet has been refactored to use a new syntax please see Sets of tasks Subtasks and Callbacks for more information The previous syntax is still supported but will be deprecated in version 1 4 e T
216. e kwargs class Schedule args kwargs clear enter entry eta None priority 0 queue TaskPool Timer TaskPool Timer TaskPool Timer TaskPool Timer askPool on_start askPool on_stop cancel tref ensure_started start stop askPool is_green True askPool rlimit_safe False askPool on_apply target args None kwargs None callback None accept_callback None ee 13 6 Internal Module Reference 345 Celery Documentation Release 2 5 5 TaskPool signal_safe False class celery concurrency eventlet Timer schedule None on_error None on_tick None kwargs class Schedule args kwargs clear enter entry eta None priority 0 queue Timer cancel tref Timer ensure_started Timer start Timer stop celery concurrency eventlet apply_target target args kwargs callback None ac cept_callback None getpid None 13 6 17 celery concurrency geventt experimental class celery concurrency gevent Schedule args kwargs clear enter entry eta None priority 0 queue class celery concurrency gevent TaskPool args kwargs class Timer schedule None on_error None on_tick None kwargs class Schedule args kwargs clear enter entry eta None priority 0 queue TaskPool Timer ensure_started TaskPool Timer start TaskPool Timer stop askPool grow n
217. e kwargs run_evdump run_evtop set_process_status prog info supports_args False celery bin celeryev main 12 36 celeryctl celery bin celeryctl class celery bin celeryct1 Command app None no_color False args create_parser prog_name command error s help option_list lt Option at 0x5c213f8 app gt lt Option at 0x5acf950 b broker gt lt Option at 0x5acf998 loader gt lt C out s fh lt open file lt stdout gt mode w at Ox7feb676e1150 gt prettify n prettify dict_ok_error n prettify list n run args kwargs run_from_argv prog_name argv show_help command usage command version 2 5 5 exception celery bin celeryctl Error reason status 1 class celery bin celeryct1 apply app None no_color False args lt task_name gt option_list lt Option at 0x5c213f8 app gt lt Option at Ox5acf950 b broker gt lt Option at Ox5acf998 loader gt lt C run name _ kw class celery bin celeryctl celeryct1 app None get_app None commands status lt class celery bin celeryctl status gt shell lt class celery bin celeryctl shell gt help lt class celer 302 Chapter 12 API Reference Celery Documeniation Release 2 5 5 enable_config_from_cmdline True execute command argv None handle_argv prog_name argv remove_options_at_beginning a
218. e Security lery exceptions SecurityError related exceptions Handle with care exception celery exceptions SoftTimeLimitExceeded The soft time limit has been exceeded This exception is raised to give the task a chance to clean up 282 Chapter 12 API Reference Celery Documeniation Release 2 5 5 exception celery exceptions SystemTerminate Signals that the worker should terminate exception celery exceptions TaskRevokedError The task has been revoked so no result available exception celery exceptions TimeLimitExceeded The time limit has been exceeded and the job has been terminated exception celery exceptions TimeoutError The operation timed out exception celery exceptions WorkerLostError The worker processing a job has exited prematurely 12 18 celery loaders e celery loaders j 12 18 1 celery loaders Loaders define how configuration is read what happens when workers start when tasks are executed and so on copyright 3 2009 2012 by Ask Solem license BSD see LICENSE for more details celery loaders current_loader args kwargs celery loaders get_loader_cls loader Get loader class by name alias celery loaders load_settings args kwargs 12 19 celery loaders app e celery loaders app j 12 19 1 celery loaders app The default loader used with custom app instances copyright 3 2009 2012 by Ask Solem license BSD see LICENSE for more d
219. e 2 5 5 134 Chapter 6 Contributing CHAPTER 7 Community Resources This is a list of external blog posts tutorials and slides related to Celery If you have a link that s missing from this list please contact the mailing list or submit a patch 135 Celery Documeniation Release 2 5 5 e Resources Who s using Celery Wiki Celery questions on Stack Overflow Mailing list Archive celery users IRC Logs e News Celery Mini Tutorial Catalan Building a Django App Server with Chef Introducci a Celery Catalan Django and Celery Death to Cron Celery Tips What s your favorite Django app Virtualenv Tips 10 Tools That Make Django Better Distributed Task Locking in Celery Celery Python Russian Celery Russian Celery RabbitMQ and sending messages directly Cron dentro do Django com Celery Portugese RabbitMQCeleryDjango Japanese Kaninchen amp Schlangen RabbitMQ amp Python German Celery Eine asynchrone Task Queue nicht nur fiir Django German Asynchronous Processing Using Celery historio us Massaging the Pony Message Queues and You Djangocon 2010 Large problems Mostly Solved Djangocon 2010 A Simple Celery with Django How To Django and asynchronous jobs Celery Django Russian Celery presentation at PyCon India 2010 celery django and virtualenv playing nice Django Task Queueing with Celery django celery presentation at DJUGL 201
220. e Time limits can now be set for individual tasks To set the soft and hard time limits for a task use the time_limit and soft_time_limit attributes 11 16 2 3 0 181 Celery Documentation Release 2 5 5 import time task time_limit 60 soft_time_limit 30 def sleeptask seconds time sleep seconds If the attributes are not set then the workers default time limits will be used New in this version you can also change the time limits for a task at runtime using the time_limit remote control command gt gt gt from celery task import control gt gt gt control time_limit tasks sleeptask soft 60 hard 120 reply 7w E ok t limi st succes orkerl example cor ime limits Only tasks that starts executing after the time limit change will be affected Note Soft time limits will still not work on Windows or other platforms that do not have the SIGUSRI1 signal e Redis backend configuration directive names changed to include the CELERY_ prefix Old setting name Replace with REDIS_HOST CELERY_REDIS_HOST REDIS_PORT CELERY_REDIS_PORT REDIS_DB CELERY_REDIS_DB REDIS_PASSWORD CELERY_REDIS_PASSWORD The old names are still supported but pending deprecation PyPy The default pool implementation used is now multiprocessing if running on PyPy 1 5 celeryd multi now supports pass through options Pass through options makes it easier to use celery without
221. e active before being expired when the max limit has been exceeded 13 6 Internal Module Reference 337 Celery Documentation Release 2 5 5 ce ce ce ce ce ce ce ce lery worker sta te SOFTWARE_INFO sw_sys Linux sw_ident celeryd sw_ver 2 5 5 Worker software platform information lery worker sta te active_requests set set of currently active Request s lery worker sta te reserved_requests set set of all reserved Request s lery worker sta the list of currently lery worker sta te revoked LimitedSet revoked tasks Persistent if statedb set te task_accepted request Updates global state when a task has been accepted lery worker sta te task_ready request Updates global state when a task is ready lery worker sta te task_reserved Updates global state when a task has been reserved lery worker sta te total_count defaultdict lt function lt lambda gt at 0x69c07d0 gt count of tasks executed by the worker sorted by type 13 6 9 celery worker strategy celery worker strategy default task app consumer 13 6 10 celery worker autoreload e celery worker autoreload j celery worker autoreload This module implements automatic module reloading class celery worker autoreload Autoreloader controller modules None monitor_cls None logger None options Tracks
222. e best practice is to use the module name as a prefix to classify the tasks using namespaces This way the name won t collide with the name from another module gt gt gt task name tasks add gt gt gt def add x y return x y gt gt gt add name J7 tasks add Which is exactly the name that is automatically generated for this task if the module name is tasks py gt gt gt task gt gt gt def add x y return x y gt gt gt add name tasks add Automatic naming and relative imports Relative imports and automatic name generation does not go well together so if you re using relative imports you should set the name explicitly For example if the client imports the module myapp tasks as tasks and the worker imports the module as myapp tasks the generated names won t match and an NotRegistered error will be raised by the worker This is also the case if using Django and using project myapp INSTALLED_APPS project myapp The worker will have the tasks registered as project myapp tasks while this is what happens in the client if the module is imported as myapp tasks gt gt gt from myapp tasks import add gt gt gt add name s add myapp tas For this reason you should never use project app but rather add the project directory to the Python path import os import sys sys path append os getcwd INSTALLED_AP
223. e class name celery loaders default Loader e TaskSet run Use celery task base TaskSet apply async instead e The module celery task rest use celery task http instead 13 3 Internals The worker e Introduction e Data structures ready_queue eta_schedule e Components Consumer ScheduleController Mediator TaskPool 13 3 1 Introduction The worker consists of 4 main components the consumer the scheduler the mediator and the task pool All these components runs in parallel working with two data structures the ready queue and the ETA schedule 316 Chapter 13 Internals Celery Documeniation Release 2 5 5 13 3 2 Data structures ready_queue The ready queue is either an instance of Queue Queue or celery buckets TaskBucket The latter if rate limiting is enabled eta_schedule The ETA schedule is a heap queue sorted by time 13 3 3 Components Consumer Receives messages from the broker using Kombu When a message is received it s converted into a celery worker job TaskRequest object Tasks with an ETA are entered into the eta_schedule messages that can be immediately processed are moved directly to the ready_queue ScheduleController The schedule controller is running the eta_schedule If the scheduled tasks eta has passed it is moved to the ready_queue otherwise the thread sleeps until the eta is met remember that the schedule is sorted by time Mediator
224. e configuration to modify task classes and their attributes The setting can be a dict or a list of annotation objects that filter for tasks and return a map of attributes to change As an example this is an annotation to change the rate_limit attribute for the tasks add task CELERY_ANNOTATIONS tasks add rate_limit 10 s or change the same for all tasks CELERY_ANNOTATIONS rate_limit 10 s You can change methods too for example the on_failure handler def my_on_failure exc task_id args kwargs einfo print Oh no Task failed Sr exc CELERY_ANNOTATIONS on_failure my_on_failure 164 Chapter 10 What s new in Celery 2 5 Celery Documeniation Release 2 5 5 If you need more flexibility then you can also create objects that filter for tasks to annotate class MyAnnotate as u def annotate task if task name startswith tasks return rate_limit 10 s CELERY_ANNOTATIONS MyAnnotate 10 4 5 current provides the currently executing task The new celery task current proxy will always give the currently executing task Example from celery task import current task task def update_twitter_status auth message twitter Twitter auth try twitter update_status message except twitter FailWhale exc current retry countdown 10 exc exc Previously you would h
225. e more often the better The necessary intermediate communication is dealt with by the Abort ableTask implementation Usage example In the consumer from celery contrib abortable import AbortableTask class MyLongRunningTask AbortableTask def run kkwargs logger get_logger kwargs results for x in TOO if x 5 0 alternatit if is_aborted kwargs logger warning Task aborted return y do_something_expensive x results append y logger info Task finished return results In the producer from myproject tasks import MyLongRunningTask def myview request async_result MyLongRunningTask delay time sleep 10 async_result abort 288 Chapter 12 API Reference Celery Documeniation Release 2 5 5 After the async_result abort call the task execution is not aborted immediately In fact it is not guaranteed to abort at all Keep checking the async_result status or call async_result wait to have it block until the task is finished Note In order to abort tasks there needs to be communication between the producer and the consumer This is currently implemented through the database backend Therefore this class will only work with the database backends class celery contrib abortable AbortableAsyncResult tfask_id backend None task_name None app None Represents a abortable result Specifically this gives the AsyncResult a abort method
226. e planning stage e DEVELOPMENT The branch is in active development but the test suite should be passing and the product should be working and possible for users to test e FROZEN The branch is frozen and no more features will be accepted When a branch is frozen the focus is on testing the version as much as possible before it is released 6 4 1 master branch The master branch is where development of the next version happens 6 4 2 Maintenance branches Maintenance branches are named after the version e g the maintenance branch for the 2 2 x series is named 2 2 Previously these were named releaseXX maint The versions we currently maintain is e 2 3 This is the current series 6 3 Versions 123 Celery Documeniation Release 2 5 5 e 2 2 This is the previous series and the last version to support Python 2 4 2 1 This is the last version to use the carrot AMQP framework Recent versions use kombu 6 4 3 Archived branches Archived branches are kept for preserving history only and theoretically someone could provide patches for these if they depend on a series that is no longer officially supported An archived version is named X Y archived Our currently archived branches are e 2 1 archived e 2 0 archived e 1 0 archived 6 4 4 Feature branches Major new features are worked on in dedicated branches There is no strict naming requirement for these branches Feature branches are r
227. e ps name using the multiprocessing process name Only works if setproctit1le is installed celery platforms set_process_title progname info None Set the ps name for the currently running process Only works if setproctit1e is installed celery platforms setegid gid Set effective group id celery platforms seteuid uid Set effective user id celery platforms setgid gid celery platforms setgroups groups celery platforms setuid uid celery platforms shellsplit s posix True celery platforms strargv argv 392 Chapter 13 Internals CHAPTER 14 Indices and tables e genindex e modindex e search 393 Celery Documeniation Release 2 5 5 394 Chapter 14 Indices and tables Python Module Index cel cel cel cel cel cel cel cel cel cel cel cel cel cel cel cel cel cel cel cel cel cel lery abstract lery app lery app abstract lery app amap lery app annotations lery app defaults lery app t lery apps lery apps lery backe lery backe lery backe lery backe lery backe lery backe lery backe lery backe lery backe lery beat ask beat worker nds nds amqp nds base nds cache nds cassandra nds database nds mongodb nds redis nds tyrant 99 29 lery bin base lery bin camqadm ery bi n cel erybeat cel e
228. e server will only delete the queue if it has no con sumers A channel error will be raised if the queue has consumers e if empty If set the server will only delete the queue if it is empty If it is not empty a channel error will be raised e nowait Do not wait for a reply durable True exchange lt unbound Exchange direct gt 362 Chapter 13 Internals Celery Documeniation Release 2 5 5 D 10 gt p p p eB O O0 O O gt gt p D A 10 Q Q Q Q Q exclusive False get no_ack None Poll the server for a new message Returns the message instance if a message was available or None otherwise Parameters no_ack If set messages received does not have to be acknowledged This method provides direct access to the messages in a queue using a synchronous dialogue de signed for specific types of applications where synchronous functionality is more important than performance name no_ack False purge nowait False Remove all ready messages from the queue queue_bind nowait False Create the queue binding on the server queue_declare nowait False passive False Declare queue on the server Parameters e nowait Do not wait for a reply e passive If set the server will not create the queue The client can use this to check whether a queue exists without modifying the server state routing_key unbind Delete the binding on the server
229. e the above constraints and you need cross language support the default setting of JSON is probably your best choice See http json org for more information pickle If you have no desire to support any language other than Python then using the pickle encoding will gain you the support of all built in Python data types except class instances smaller messages when send ing binary files and a slight speedup over JSON processing See http docs python org library pickle html for more information yaml YAML has many of the same characteristics as json except that it natively supports more data types in cluding dates recursive references etc However the Python libraries for YAML are a good bit slower than the libraries for JSON If you need a more expressive set of data types and need to maintain cross language compatibility then YAML may be a better fit than the above See http yaml org for more information msgpack msgpack is a binary serialization format that is closer to JSON in features It is very young however and support should be considered experimental at this point See http msgpack org for more information The encoding used is available as a message header so the worker knows how to deserialize any task If you use a custom serializer this serializer must be available for the worker The client uses the following order to decide which serializer to use when sending a task 1 The serializer
230. e the following task task def process_upload filename tmpfile increment_file_ counter add_file_metadata_to_db filename tmpfile copy_file_to_destination filename tmpfile If this crashed in the middle of copying the file to its destination the world would contain incomplete state This is not a critical scenario of course but you can probably imagine something far more sinister So for ease of programming we have less reliability It s a good default users who require it and know what they are doing can still enable acks_late and in the future hopefully use manual acknowledgement In addition Task retry has features not available in AMQP transactions delay between retries max retries etc So use retry for Python errors and if your task is idempotent combine that with acks_late if that level of reliability is required 9 7 16 Can I schedule tasks to execute at a specific time Answer Yes You can use the eta argument of Task apply_async Or to schedule a periodic task at a specific time use the celery schedules crontab schedule behavior from celery schedules import crontab from celery task import periodic_task periodic_task run_every crontab hour 7 minute 30 day_of_week mon def every monday _morning print This is run every Monday morning at 7 30 9 7 17 How do I shut down celeryd safely Answer Use the TERM signal and the worker will finish all currently executing jobs and shut down
231. e who are not using south a normal syncdb will work python manage py syncdb By default Celery uses RabbitMQ as the broker but there are several alternatives to choose from see Choosing your Broker All settings mentioned in the Celery documentation should be added to your Django project s sett ings py module For example we can configure the BROKER_URL setting to specify what broker to use BROKER_URL amqp guest guest localhost 5672 That s it 109 Celery Documeniation Release 2 5 5 Special note for mod_wsgji users If you re using mod_wsgi to deploy your Django application you need to include the following in your wsgi module import djcelery djcelery setup_loader 4 1 2 Defining and executing tasks Tasks are defined by wrapping functions in the task decorator It is a common practice to put these in their own module named tasks py and the worker will automatically go through the apps in INSTALLED_APPS to import these modules For a simple demonstration we can create a new Django app called celerytest To create this app you need to be in the directoryw of your Django project where manage py is located and execute python manage py startapp celerytest After our new app has been created we can define our task by editing a new file called celerytest tasks py from celery task import task task def add x y return x y Our example task is pretty pointless it just returns t
232. eap wait until pool worker available etc is now handled by multiprocessing Pool itself e Convert statistics data to Unicode for use as kwargs Thanks Lucy 11 48 0 4 1 release date 2009 07 02 01 42 P M CET e Fixed a bug with parsing the message options mandatory routing_key priority immediate 11 49 0 4 0 release date 2009 07 01 07 29 P M CET e Adds eager execution celery execute apply Task apply executes the function blocking until the task is done for API compatibility it returns an celery result EagerResult instance You can configure celery to always run tasks locally by setting the CELERY_ALWAYS_EAGER setting to True e Now depends on anyjson e 99 coverage using python coverage 3 0 11 50 0 3 20 release date 2009 06 25 08 42 P M CET New arguments to apply_async the advanced version of delay_task countdown and eta gt gt gt un 1 2 in e future gt gt gt res apply_async MyTask countdown 10 gt gt gt Ru lay from n gt gt gt res apply_async MyTask eta datetime now timedelta days 1 Now unlinks stale PID files Lots of more tests Now compatible with carrot gt 0 5 0 IMPORTANT The subtask_ids attribute on the TaskSetResult instance has been removed To get this informa tion instead use gt gt gt subtask_ids subtask task_id for subtask in ts_res subtasks Taskset run now respects extra message options from the task class
233. ease 2 5 Date February 04 2014 13 1 Contributors Guide to the Code e Philosophy The API gt RCP Precedence Rule e Conventions and Idioms Used Classes x Naming Default values x Exceptions x Composites e Applications vs single mode e Module Overview 13 1 1 Philosophy The API gt RCP Precedence Rule e The API is more important than Readability e Readability is more important than Convention e Convention is more important than Performance unless the code is a proven hotspot More important than anything else is the end user API Conventions must step aside and any suffering is always alleviated if the end result is a better API 311 Celery Documentation Release 2 5 5 13 1 2 Conventions and Idioms Used Classes Naming Follows PEP 8 e Class names must be CamelCase e but not if they are verbs verbs shall be lower_case class TestMyClass Case BAD pass class test_MyClass Case pass class TestMyFunction Case BAD pass class test_my_function Case pass verb dateTwitterStatus object BAD y action class class Up pass class update_twitter_status object GOOD pass Note Sometimes it makes sense to have a class mask as a function and there is precedence for this in the stdlib e g contextmanager Celery examples include subtask chord inspect promise and more e Factory functions and methods must be CamelCase
234. eate our celeryconfig py 1 Configure how we communicate with the broker RabbitMQ in this example 1 3 First steps with Celery 13 Celery Documeniation Release 2 5 5 BROKER_URL amqp guest guest localhost 5672 2 Define the backend used to store task metadata and return values CELERY_RESULT_BACKEND amqp The AMQP backend is non persistent by default and you can only fetch the result of a task once as it s sent as a message For list of backends available and related options see Task result backend settings 3 Finally we list the modules the worker should import This includes the modules containing your tasks We only have a single task module tasks py which we added earlier CE H 1ERY_IMPORTS tasks That s it There are more options available like how many processes you want to use to process work in parallel the CELERY_CONCURRENCY setting and we could use a persistent result store backend but for now this should do For all of the options available see Configuration and defaults Note You can also specify modules to import using the 7 option to celeryd celeryd l info I tasks handlers This can be a single or a comma separated list of task modules to import when celeryd starts 1 3 4 Running the celery worker server To test we will run the worker server in the foreground so we can see what s going on in the
235. econds 12 14 celery signals e celery signals j 12 14 1 celery signals See Signals copyright 3 2009 2012 by Ask Solem license BSD see LICENSE for more details 12 15 celery security celery security disable_untrusted_serializers whitelist None celery security setup_security allowed_serializers None key None cert None store None digest shal serializer json Setup the message signing serializer Disables untrusted serializers and if configured to use the auth serializer will register the auth serializer with the provided settings into the Kombu serializer registry Parameters e allowed_serializers List of serializer names or content_types that should be exempt from being disabled key Name of private key file to use Defaults to the CELERY_SECURITY_KEY setting cert Name of certificate file to use Defaults to the CELERY _SECURITY_CERTIFICATE setting e store Directory containing certificates Defaults to the CELERY_SECURITY_CERT_STORE setting digest Digest algorithm used when signing messages Default is shal serializer Serializer used to encode messages after they have been signed See CELERY_TASK_SERIALIZER for the serializers supported Default is json 12 16 celery utils mail e celery utils mail j 280 Chapter 12 API Reference Celery Documeniation Release 2 5 5 1
236. ect etc default celeryd Where to cl RYD_CHDIR opt Myproject AL zi CELE Ext ts to celeryd CELER time limit 300 concurrency 8 Name of the celery config m es CELERY_CONFIG_MODULE celeryconfig ced with the no be re me Wit CELERYD_LOG_FIL var log celery n log CELERYD_PID_FILE var run celery n pid CELERYD_USER celery CELERYD_GROUP celery Example Django configuration This is an example configuration for those using django celery ame of nodes to start here we have a single node CELERYD_NODES w1 or we could have three nodes CELERYD_NODES wl w2 w3 Where to chdir at start CELERYD_CHDIR opt Myproject 7 How to call manage py celeryd_multi CELERYD_MULTI SCELERYD_CHDIR manage py celeryd_multi T How to call manage py celeryctl CELERYCTL CELERYD_CHDIR manage py celeryctl Extra arguments to celeryd CELERYD_OPTS time limit 300 concurrency 8 Name of the celery config module RY_CONFIG_MODULE celeryconfig Q H ole will be replaced with the nodename RYD_LOG_FILE var log celery n log RYD_PID_FILE var run celery n pid T S z 5 2 Running celeryd as a daemon 115 Celery Documentation Release 2 5 5 W
237. ed backend BROKER_USER Username to connect as BROKER_PASSWORD Password to connect with BROKER_VHOST Virtual host Default is BROKER_USE_SSL Use SSL to connect to the broker Off by default This may not be supported by all transports BROKER_POOL_LIMIT New in version 2 3 The maximum number of connections that can be open in the connection pool The pool is enabled by default since version 2 5 with a default limit of ten connections This number can be tweaked depending on the number of threads greenthreads eventlet gevent using a connection For example running eventlet with 1000 greenlets that use a connection to the broker contention can arise and you should consider increasing the limit If set to None or 0 the connection pool will be disabled and connections will be established and closed for every use Default since 2 5 is to use a pool of 10 connections 96 Chapter 3 Configuration and defaults Celery Documeniation Release 2 5 5 BROKER_CONNECTION_TIMEOUT The default timeout in seconds before we give up establishing a connection to the AMQP server Default is 4 seconds BROKER_CONNECTION_RETRY Automatically try to re establish the connection to the AMQP broker if lost The time between retries is increased for each retry and is not exhausted before BROKER_CONNECTION_MAX_RETRIES is exceeded This behavior is on by default BROKER_CONNECTION_MAX_RETRIES Maximu
238. ed from the result queue It is unlikely we will receive any after 5 seconds with no worker processes celerybeat Now creates pidfile even if the det ach option is not set eventlet gevent The broadcast command consumer is now running in a separate greenthread This ensures broadcast commands will take priority even if there are many active tasks Internal module celery worker controllers renamed to celery worker mediator celeryd Threads now terminates the program by calling os _exit as it is the only way to ensure exit in the case of syntax errors or other unrecoverable errors Fixed typo in maybe_t imedelta Issue 352 celeryd Broadcast commands now logs with loglevel debug instead of warning AMQP Result Backend Now resets cached channel if the connection is lost Polling results with the AMQP result backend was not working properly Rate limits No longer sleeps if there are no tasks but rather waits for the task received condition Performance improvement ConfigurationView iter dict should return keys not items Issue 362 celerybeat PersistentScheduler now automatically removes a corrupted schedule file Issue 346 Programs that doesn t support positional command line arguments now provides a user friendly error message Programs no longer tries to load the configuration file when showing version Issue 347 Autoscaler The all processes busy log message is now severity debug instead of error celery
239. ed they can drastically reduce performance especially on systems processing lots of tasks This option is useful on low traffic workers that experience errors as a result of cached database connections going stale through inactivity For example intermittent errors like OperationalError 2006 MySQL server has gone away can be fixed by enabling short lived sessions This option only affects the database backend Example configuration CELERY_RESULT_BACKEND database CELERY_RESULT_DBURI mysql user password host dbname 3 2 7 AMQP backend settings Note The AMQP backend requires RabbitMQ 1 1 0 or higher to automatically expire results If you are running an older version of RabbitmQ you should disable result expiration like this CELERY_TASK_RESULT_EXPIRES None 90 Chapter 3 Configuration and defaults Celery Documeniation Release 2 5 5 CELERY_RESULT_EXCHANGE Name of the exchange to publish results in Default is celeryresults CELERY_RESULT_EXCHANGE_TYPE The exchange type of the result exchange Default is to use a direct exchange CELERY_RESULT_PERSISTENT If set to True result messages will be persistent This means the messages will not be lost after a broker restart The default is for the results to be transient Example configuration CELERY_RESULT_BACKEND amqp CELERY_TASK RESULT_EXPIRES 18000 5 hours H 3
240. ed to be processed it s moved over the the ready_queue The celery worker mediator is then responsible for moving tasks from the ready_queue to the worker pool copyright 3 2009 2012 by Ask Solem license BSD see LICENSE for more details class celery worker buckets FastQueue maxsize 0 Queue Queue supporting the interface of TokenBucket Queue clear expected_time fokens 1 items wait block True 334 Chapter 13 Internals Celery Documeniation Release 2 5 5 exception celery worker buckets RateLimitExceeded The token buckets rate limit has been exceeded class celery worker buckets TaskBucket fask_registry This is a collection of token buckets each task type having its own token bucket If the task type doesn t have a rate limit it will have a plain Queue object instead of a TokenBucket Queue The put operation forwards the task to its appropriate bucket while the get operation iterates over the buckets and retrieves the first available item Say we have three types of tasks in the registry twitter update feed refresh and video compress the TaskBucket will consist of the following items twitter update TokenBucketQueue fill_rate 300 feed refresh Queue vyideo compress TokenBucketQueue fill_rate 2 The get operation will iterate over these until one of the buckets is able to return an item The underlying datastructure is a dict so the order is ignored here
241. een set so far and the rest of __ init __ has not been executed e conf The configuration of the current app worker_init Dispatched before the worker is started worker_ready Dispatched when the worker is ready to accept work 2 13 Signals 83 Celery Documeniation Release 2 5 5 worker_process_init Dispatched by each new pool worker process when it starts worker_shutdown Dispatched when the worker is about to shut down Celerybeat Signals beat_init Dispatched when celerybeat starts either standalone or embedded Sender is the celery beat Service in stance beat_embedded_init Dispatched in addition to the beat_init signal when celerybeat is started as an embedded process Sender is the celery beat Service instance Eventlet Signals eventlet_pool_started Sent when the eventlet pool has been started Sender is the celery concurrency eventlet TaskPool instance eventlet_pool_preshutdown Sent when the worker shutdown just before the eventlet pool is requested to wait for remaining workers Sender is the celery concurrency eventlet TaskPool instance eventlet_pool_postshutdown Sent when the pool has been joined and the worker is ready to shutdown Sender is the celery concurrency eventlet TaskPool instance eventlet_pool_apply Sent whenever a task is applied to the pool Sender is the celery concurrency eventlet TaskPool instance Provides arguments e target 84 Chapter
242. elease 2 5 5 With smaller tasks you can process more tasks in parallel and the tasks won t run long enough to block the worker from processing other waiting tasks However executing a task does have overhead A message needs to be sent data may not be local etc So if the tasks are too fine grained the additional overhead may not be worth it in the end See also The book Art of Concurrency has a whole section dedicated to the topic of task granularity Data locality The worker processing the task should be as close to the data as possible The best would be to have a copy in memory the worst would be a full transfer from another continent If the data is far away you could try to run another worker at location or if that s not possible cache often used data or preload data you know is going to be used The easiest way to share data between workers is to use a distributed cache system like memcached See also The paper Distributed Computing Economics by Jim Gray is an excellent introduction to the topic of data locality State Since celery is a distributed system you can t know in which process or on what machine the task will be executed You can t even know if the task will run in a timely manner The ancient async sayings tells us that asserting the world is the responsibility of the task What this means is that the world view may have changed since the task was requested so the task is responsible fo
243. elery Documeniation Release 2 5 5 9 1 General 9 1 1 What kinds of things should I use Celery for Answer Queue everything and delight everyone is a good article describing why you would use a queue in a web context These are some common use cases e Running something in the background For example to finish the web request as soon as possible then update the users page incrementally This gives the user the impression of good performance and snappiness even though the real work might actually take some time e Running something after the web request has finished e Making sure something is done by executing it asynchronously and using retries e Scheduling periodic work And to some degree e Distributed computing e Parallel execution 9 2 Misconceptions 9 2 1 Is Celery dependent on pickle Answer No Celery can support any serialization scheme and has built in support for JSON YAML Pickle and msgpack Also as every task is associated with a content type you can even send one task using pickle and another using JSON The default serialization format is pickle simply because it is convenient it supports sending complex Python objects as task arguments If you need to communicate with other languages you should change to a serialization format that is suitable for that You can set a global default serializer the default serializer for a particular Task or even what serializer to use when sending
244. eleryctl migrate django redis Routers can now override the exchange and routing_key used to create missing queues Issue 577 By default this will always use the name of the queue but you can now have a router return exchange and routing_key keys to set them This is useful when using routing classes which decides a destination at runtime Contributed by Akira Matsuzaki Redis result backend Adds support for a max_connections parameter 166 Chapter 10 What s new in Celery 2 5 Celery Documeniation Release 2 5 5 It is now possible to configure the maximum number of simultaneous connections in the Redis con nection pool used for results The default max connections setting can be configured using the CELERY_REDIS_MAX_ CONNECTIONS setting or it can be changed individually by RedisBackend max_connections int Contributed by Steeve Morin Redis result backend Adds the ability to wait for results without polling Contributed by Steeve Morin MongoDB result backend Now supports save and restore taskset Contributed by Julien Poissonnier There s a new Security guide in the documentation The init scripts has been updated and many bugs fixed Contributed by Chris Streeter User tilde is now expanded in command line arguments Can now configure CELERYCTL enwvar in etc default celeryd While not necessary for operation celeryctl is used for the celeryd status command and the path to
245. elivery_info See celery task base Task run for more information Magic keyword arguments are deprecated and will be removed in version 3 0 classmethod from_message message body kwargs hostname id info safe False internal_error_msg Task name s id s INTERNAL ERROR exc s n Format string used to log internal error kwargs logger maybe_expire If expired mark the task as revoked name on_accepted pid time_accepted Handler called when task is accepted by worker pool on_ack on_failure exc_info Handler called if the task raised an exception on_retry exc_info Handler called if the task should be retried 332 Chapter 13 Internals Celery Documeniation Release 2 5 5 on_success ret_value now None Handler called if the task was successfully processed on_timeout soft timeout Handler called if the task times out repr_result result maxlen 46 request_dict retry_msg Task name s id s retry exc s Format string used to log task retry revoked If revoked skip task and mark state send_event type fields shortinfo store_errors success_msg Task name s id s succeeded in runtime ss return_value s n Format string used to log task success task task_id task_name terminate pool signal None time_start tzlocal worker _ pid class celery worker job TaskRequest name id args kwargs eta None expires
246. emoved once they have been merged into a release branch 6 5 Tags Tags are used exclusively for tagging releases A release tag is named with the format vX Y Z e g v2 3 1 Experimental releases contain an additional identifier vX Y Z id e g v3 0 0 rc1 Experimental tags may be removed after the official release 6 6 Working on Features amp Patches Note Contributing to Celery should be as simple as possible so none of these steps should be considered mandatory You can even send in patches by email if that is your preferred work method We won t like you any less any contribution you make is always appreciated However following these steps may make maintainers life easier and may mean that your changes will be accepted sooner 6 6 1 Forking and setting up the repository First you need to fork the Celery repository a good introduction to this is in the Github Guide Fork a Repo After you have cloned the repository you should checkout your copy to a directory on your machine git clone git github com username celery git 124 Chapter 6 Contributing Celery Documeniation Release 2 5 5 When the repository is cloned enter the directory to set up easy access to upstream changes cd celery git remote add upstream git github com celery celery git git fetch upstream If you need to pull in new changes from upstream you should always use the rebase option to git pull git pull rebase upstre
247. en an unregistered task is received 13 6 4 celery worker job e celery worker job j celery worker job This module defines the Request class which specifies how tasks are executed copyright 3 2009 2012 by Ask Solem license BSD see LICENSE for more details class celery worker job Request body on_ack lt function noop at OxIcaf668 gt host name None logger None eventer None app None con nection_errors None request_dict None delivery_info None task None opts A request for task execution acknowledge Acknowledge task acknowledged app args 13 6 Internal Module Reference 331 Celery Documentation Release 2 5 5 connection_errors delivery info error_msg Task name s id s raised exception exc s n Format string used to log task failure eta eventer execute loglevel None logfile None Execute the task ina trace_task Parameters e loglevel The loglevel used by the task logfile The logfile used by the task execute_using_pool pool loglevel None logfile None Like execute but using a worker pool Parameters e pool A multiprocessing Pool instance e loglevel The loglevel used by the task e logfile The logfile used by the task expires extend_with_default_kwargs loglevel logfile Extend the tasks keyword arguments with standard task arguments Currently these are logfile loglevel task_id task_name task_retries and d
248. ency None consumer_cls None disable _rate_limits None eta_scheduler_cls None eta_scheduler_precision None force_execv None logfile None loglevel 40 max_tasks_per_child None mediator_cls None on_timer_error einfo on_timer_tick delay pool_cls None pool_putlocks None prefetch_multiplier None process_task request Process task by sending it to the pool of workers reload modules None reload False reloader None 296 Chapter 12 API Reference Celery Documeniation Release 2 5 5 ce ce ce ce Wor Wor Wor Wor Wor Wor Wor Wor Wor Wor Wor Wor Wor Wor Wor Wor Wor Wor Wor schedule _ filename None scheduler_cls None send_events None start Starts the workers main loop state state_db None stop in_sighandler False Graceful shutdown of the worker server task_soft_time_ limit None task_time_1limit None terminate in_sighandler False Ker Ker Ker Ker Ker Ker Ker Ker Ker Ker Ker Ker Ker KOT Ker Ker Ker Ker Ker Not so graceful shutdown of the worker server die msg exitcode 1 extra_info inherit_confopts lt class celery worker WorkController gt init_loader init_queues install_platform_tweaks worker Install platform specific tweaks and workarounds Lloglevel None on_consumer
249. ents to pass on to the task a dict countdown Number of seconds into the future that the task should execute Defaults to immediate execution do not confuse with the immediate flag as they are unrelated eta A datetime object describing the absolute time and date of when the task should be executed May not be specified if countdown is also supplied Do not confuse this with the immediate flag as they are unrelated expires Either a int describing the number of seconds or a datet ime object that describes the absolute time and date of when the task should expire The task will not be executed after the expiration time connection Re use existing broker connection instead of establishing a new one retry If enabled sending of the task message will be retried in the event of connection loss or failure Default is taken from the CELERY_TASK_PUBLISH_RETRY setting Note you need to handle the publisher connection manually for this to work retry_policy Override the retry policy used See the CELERY_TASK_PUBLISH_RETRY setting routing_key The routing key used to route the task to a worker server Defaults to the routing_key attribute exchange The named exchange to send the task to Defaults to the exchange attribute 250 Chapter 12 API Reference Celery Documeniation Release 2 5 5 e exchange_type The exchange type to initialize the exchange if not already dec
250. eption BaseException and object If that happens you should use UnpickleableException instead Parameters exc An exception instance Returns the nearest exception if it s not Exception or below if it is it returns None rtype Exception celery utils serialization get_pickleable_ exception exc Make sure exception is pickleable celery utils serialization get_pickled_exception exc Get original exception from exception pickled using get_pickleable_exception celery utils serialization subclass_exception name parent module celery utils serialization unwanted_base_classes lt type exceptions StandardError gt lt type exceptions E List of base classes we probably don t want to reduce to 13 6 52 celery utils threads class celery utils threads Event verbose None class celery utils threads Thread group None target None name None args kwargs None verbose None class celery utils threads bgThread name None kwargs body on_crash exc_info msg fmt kwargs run 384 Chapter 13 Internals Celery Documeniation Release 2 5 5 stop Graceful shutdown 13 6 53 celery utils timer2 e timer2 timer2 Scheduler for Python functions copyright 3 2009 2012 by Ask Solem license BSD see LICENSE for more details class celery utils timer2 Entry fun args None kwargs None cancel cancelled False
251. er awesome Wt Ur Ww tH 6 7 Coding Style You should probably be able to pick up the coding style from surrounding code but it is a good idea to be aware of the following conventions e All Python code must follow the PEP 8 guidelines pep8 py is an utility you can use to verify that your code is following the conventions e Docstrings must follow the PEP 257 conventions and use the following style Do this 6 7 Coding Style 127 Celery Documeniation Release 2 5 5 def method arg Short description More details ww or def method arg wrwshort description but not this def method arg ww Short description ww e Lines should not exceed 78 columns You can enforce this in vim by setting the textwidth option set 78 If adhering to this limit makes the code less readable you have one more character to go on which means 78 is a soft limit and 79 is the hard limit e Import order Python standard library import xxx Python standard library from xxx import Third party packages Other modules from the current package or in case of code using Django Python standard library import xxx Python standard library from xxx import Third party packages Django packages Other modules from the current package Within these sections the imports should be sorted by module name Example import threading import time from collections
252. er is shut down properly If you hit this problem you have to kill all workers manually and restart them ps auxww grep celeryd awk print 2 xargs kill You might have to wait a while until all workers have finished the work they re doing If it s still hanging after a long time you can kill them by force with ps auxww grep celeryd awk print 2 xargs kill 9 9 3 8 Why won t my Task run Answer There might be syntax errors preventing the tasks module being imported You can find out if Celery is able to run the task by executing the task manually gt gt gt from myapp tasks import MyPeriodicTask gt gt gt MyPeriodicTask delay Watch celeryd s log file to see if it s able to find the task or if some other error is happening 9 3 9 Why won t my periodic task run Answer See Why won t my Task run 9 3 Troubleshooting 153 Celery Documeniation Release 2 5 5 9 3 10 How do I discard all waiting tasks Answer You can use celeryctl to purge all configured task queues celeryctl purge or programatically gt gt gt from celery task control import discard_all gt gt gt discard_all 1753 If you only want to purge messages from a specific queue you have to use the AMQP API or the camqadm utility camqadm queue purge lt queue name gt The number 1753 is the number of messages deleted You can also start celeryd with the purge argument to purge
253. ers listen to different queues gt gt gt add apply_async args filename routing_key video compress gt gt gt add apply_async args filename 360 routing_key image rotate gt gt gt add apply_async args filename selection g routing_key image crop gt gt gt add apply_async routing_key misc recommend Later if the crop task is consuming a lot of resources we can bind new workers to handle just the image crop task by creating a new queue that binds to image crop See also To find out more about routing please see Routing Tasks 2 3 7 AMQP options e mandatory This sets the delivery to be mandatory An exception will be raised if there are no running workers able to take on the task Not supported by amqplib e immediate Request immediate delivery Will raise an exception if the task cannot be routed to a worker immediately Not supported by amqplib e priority A number between 0 and 9 where 0 is the highest priority Note RabbitMQ does not yet support AMQP priorities 2 4 Workers Guide 2 4 Workers Guide 41 Celery Documentation Release 2 5 5 e Starting the worker e Stopping the worker e Restarting the worker e Concurrency e Persistent revokes e Time limits Changing time limits at runtime e Max tasks per child setting e Autoreloading e Remote control The broadcast function Rate limits Revoking tasks Remote shutdown
254. ery Documeniation Release 2 5 5 BaseBacke Prepare BaseBacke BaseBacke Prepare BaseBacke nd prepare_exception exc exception for serialization nd prepare_expires value type None nd prepare_value result value for storage nd process_cleanup Cleanup actions to do at the end of a task worker process BaseBacke Reload BaseBacke Reload BaseBacke Get the BaseBacke nd reload_task_result task_id task result even if it has been previously fetched nd reload_taskset_result task_id taskset result even if it has been previously fetched nd restore_taskset taskset_id cache True result of a taskset nd save_taskset taskset_id result Store the result and status of a task BaseBacke nd store_result task_id result status traceback None Store the result and status of a task BaseBacke nd subpolling_ interval None Time to sleep between polling each individual item in ResultSet iterate as opposed to the interval argu ment which is for each pass BaseBackend supports_native_join False If true the backend must implement get_many BaseBackend wait_for task_id timeout None propagate True interval 0 5 Wait for task and return its result If the task raises an exception this exception will be re raised by wait_for If timeout is not None this raises the celery exceptions TimeoutError exception if the oper ation takes longer than timeout seconds
255. ery Integration git https github com celery django celery PyPI http pypi python org pypi django celery docs http docs celeryproject org en latest django 6 9 7 cl Actor framework git https github com celery cl PyPI http pypi python org pypi cl 6 9 8 cyme Distributed Celery Instance manager git https github com celery cyme PyPI http pypi python org pypi cyme docs http cyme readthedocs org 6 9 9 Deprecated e Flask Celery git https github com ask Flask Celery PyPI http pypi python org pypi Flask Celery e carrot git https github com ask carrot PyPI http pypi python org pypi carrot e ghettoq 6 9 Packages 131 Celery Documentation Release 2 5 5 git https github com ask ghettoq PyPI http pypi python org pypi ghettoq e kombu sqlalchemy git https github com ask kombu sqlalchemy PyPI http pypi python org pypi kombu sqlalchemy e django kombu git https github com ask django kombu PyPI http pypi python org pypi django kombu e pylibrabbitmq Old name for Librabbitma git None PyPI http pypi python org pypi pylibrabbitmq 6 10 Release Procedure 6 10 1 Updating the version number The version number must be updated two places e celery __init__ py e docs include introduction txt After you have changed these files you must render the README files There is a script to convert sphinx syntax to generic reStructured Text syntax and the paver task readme does this for
256. es to code infrastructure policy documentation and translations during a release may negatively impact others work 6 1 2 Be respectful The Celery community and its members treat one another with respect Everyone can make a valuable contribution to Celery We may not always agree but disagreement is no excuse for poor behavior and poor manners We might all experience some frustration now and then but we cannot allow that frustration to turn into a personal attack It s important to remember that a community where people feel uncomfortable or threatened is not a productive one We expect members of the Celery community to be respectful when dealing with other contributors as well as with people outside the Celery project and with users of Celery 6 1 3 Be collaborative Collaboration is central to Celery and to the larger free software community We should always be open to collab oration Your work should be done transparently and patches from Celery should be given back to the community when they are made not just when the distribution releases If you wish to work on new code for existing upstream projects at least keep those projects informed of your ideas and progress It many not be possible to get consensus from upstream or even from your colleagues about the correct implementation for an idea so don t feel obliged to have that agreement before you begin but at least keep the outside world informed of your work and publish your
257. es periodic tasks by default but a new daemon has been intro duced celerybeat To launch the periodic task scheduler you have to run celerybeat celerybeat Make sure this is running on one server only if you run it twice all periodic tasks will also be executed twice If you only have one worker server you can embed it into celeryd like this celeryd beat Embed celerybeat in celeryd e The supervisor has been removed This means the S and supervised options to celeryd is no longer supported Please use something like http supervisord org instead e TaskSet join has been removed use TaskSetResult join instead e The task status DONE has been renamed to SUCCESS e AsyncResult is_done has been removed use AsyncResult successful instead e The worker no longer stores errors if Task ignore_result is set to revert to the previous behaviour set CELERY_STORE_ERRORS_EVEN_IF_IGNORED to True e The statistics functionality has been removed in favor of events so the S and statistics switches has been removed e The module celery task strategy has been removed e celery discovery has been removed and it s autodiscover function is now in celery loaders djangoapp Reason Internal API e The CELERY_LOADER environment variable now needs loader class name in addition to module name E g where you previously had celery loaders default you
258. essage ack for message in messages_for_url url consumer close connection close 8 3 4 View and URLs This is also simple stuff don t think I have to explain this code to you The interface is as follows if you have a link to http google com you would want to count the clicks for you replace the URL with http mysite clickmuncher count u http google com and the count view will send off an increment message and forward you to that site clickmuncher views py from django http import HttpResponseRedirect from clickmuncher messaging import send_increment_clicks def count request url request GET u send_increment_clicks url return HttpResponseRedirect url clickmuncher urls py 8 3 Tutorial Creating a click counter using Kombu and celery 147 Celery Documentation Release 2 5 5 from django conf urls defaults import patterns url from clickmuncher import views urlpatterns patterns url r S views count name clickmuncher count 8 3 5 Creating the periodic task Processing the clicks every 30 minutes is easy using celery periodic tasks clickmuncher tasks py from celery task import PeriodicTask from clickmuncher messaging import process_clicks from datetime import timedelta class ProcessClicksTask PeriodicTask run_every timedelta minutes 30 def run self kwargs process_clicks We subclass from celery task base PeriodicTask set the run_every attr
259. essing Using Celery historio us http blog historio us asynchronous processing using celery 7 2 18 Massaging the Pony Message Queues and You Djangocon 2010 http www slideshare net shawnrider massaging the pony message queues and you 7 2 19 Large problems Mostly Solved Djangocon 2010 http www slideshare net ericholscher large problems 7 2 20 A Simple Celery with Django How To http shawnmilo blogspot com 2010 07 simple celery with django how to html 7 2 21 Django and asynchronous jobs http www davidfischer name 2010 09 django and asynchronous jobs 7 2 22 Celery Django Russian http www proft com ua 2010 09 4 celery dobavlyaem parallelizm v django 7 2 23 Celery presentation at PyCon India 2010 http in pycon org 2010 talks S0 python celery http in pycon org 2010 static files talks 50 mahendra celery pycon 2010 pdf 7 2 24 celery django and virtualenv playing nice http tumblr whatupderek com post 1072002968 celery django and virtualenyv playing nice 7 2 25 Django Task Queueing with Celery http justinvoss wordpress com 20 1 0 06 22 django task queueing with celery 7 2 26 django celery presentation at DJUGL 2010 http www slideshare net matclayton django celery 7 2 27 Django Celery Quickstart or how learned to stop using cron and love cel ery http bitkickers blogspot com 2010 07 djangocelery quickstart or how i html 7 2 News 139 Celery Documentation
260. et_logger kwargs logger info log_result got s result Invocation gt gt gt add delay 2 2 callback log_result subtask See Sets of tasks Subtasks and Callbacks for more information 9 7 10 Can I cancel the execution of a task Answer Yes Use result revoke 9 7 Tasks 157 Celery Documentation Release 2 5 5 gt gt gt result add apply_async args 2 2 countdown 120 gt gt gt result revoke or if you only have the task id gt gt gt from celery task control import revoke gt gt gt revoke task_id 9 7 11 Why aren t my remote control commands received by all workers Answer To receive broadcast remote control commands every worker node uses its host name to create a unique queue name to listen to so if you have more than one worker with the same host name the control commands will be received in round robin between them To work around this you can explicitly set the host name for every worker using the hostname argument to celeryd celeryd hostname S hostname 1 celeryd hostname S hostname 2 etc etc 9 7 12 Can I send some tasks to only some servers Answer Yes You can route tasks to an arbitrary server using AMQP and a worker can bind to as many queues as it wants See Routing Tasks for more information 9 7 13 Can I change the interval of a periodic task at runtime Answer Yes You can use the Django database scheduler or you can
261. etails class celery loaders app AppLoader app None kwargs 12 18 celery loaders 283 Celery Documentation Release 2 5 5 on_worker_init read_configuration 12 20 celery loaders default e celery loaders default j 12 20 1 celery loaders default The default loader used when no custom app has been initialized copyright 3 2009 2012 by Ask Solem license BSD see LICENSE for more details class celery loaders default Loader app None kwargs The loader used by the default app find_module module on_worker_init Imports modules at worker init so tasks can be registered and used by the worked The list of modules to import is taken from the CELERY_IMPORTS setting read_configuration Read configuration from celeryconfig py and configure celery and Django so it can be used by regular Python setup_settings settingsdict wanted module item item 12 21 celery loaders base e celery loaders base j 12 21 1 celery loaders base Loader base class copyright 3 2009 2012 by Ask Solem license BSD see LICENSE for more details 284 Chapter 12 API Reference Celery Documeniation Release 2 5 5 class celery loaders base BaseLoader app None kwargs The base class for loaders Loaders handles Reading celery client worker configurations What happens when a task starts See on_task_init What happens when the worker starts See on_wo
262. everal tasks at once and is then able to join the results in the same order as the tasks were invoked A task set takes a list of subtask s gt gt gt from celery task sets import TaskSet gt gt gt from tasks import add gt gt gt job TaskSet tasks add subtask add subtask add subtask add subtask 4 4 8 8 16 16 82 32 gt gt gt result job apply_async 54 Chapter 2 User Guide Celery Documeniation Release 2 5 5 gt gt gt result ready True gt gt gt result successful True gt gt gt result join 4 8 16 32 64 Results When a TaskSet is applied it returns a TaskSetResult object TaskSetResult takes a list of AsyncResult instances and operates on them as if it was a single task It supports the following operations e successful Returns True if all of the subtasks finished successfully e g did not raise an exception e failed Returns True if any of the subtasks failed e waiting Returns True if any of the subtasks is not ready yet e ready Return True if all of the subtasks are ready e completed_count Returns the number of completed subtasks e revoke Revokes all of the subtasks iterate Iterates over the return values of the subtasks as they finish one by one e join Gather the results for all of the subtasks and return a list with them ordered by the order of which they were called 2 6 3 Chords
263. eviously saved itersubtasks Depreacted Use iter self results instead classmethod restore taskset_id backend None Restore previously saved taskset result results None List iterator of results in the taskset save backend None Save taskset result for later retrieval using restore 272 Chapter 12 API Reference Celery Documeniation Release 2 5 5 Example gt gt gt result save gt gt gt result TaskSetResult restore taskset_id taskset_id None The UUID of the taskset 12 10 celery actors 12 11 celery task control e celery task control j 12 11 1 celery task control Client for worker remote control commands Server implementation is in celery worker control copyright 3 2009 2012 by Ask Solem license BSD see LICENSE for more details class celery task control Control app class Mailbox namespace type direct connection None Node hostname None state None channel None handlers None abcast command kwargs call destination command kwargs timeout None callback None channel None cast destination command kwargs connection None exchange None exchange_fmt s pidbox get_queue hostname get_reply_ queue ticket multi_call command kwargs timeout 1 limit None callback None channel None namespace None node_cls alias of Node reply exchange None reply _exchange_fmt reply s pidbox 12 10 ce
264. eway in the Celery distribution http github com celery celery tree master examples celery_http_gateway 2 8 Routing Tasks Note Alternate routing concepts like topic and fanout may not be available for all transports please consult the transport comparison table 58 Chapter 2 User Guide Celery Documeniation Release 2 5 5 e Basics Automatic routing x Changing the name of the default queue x How the queues are defined Manual routing e AMQP Primer Messages Producers consumers and brokers Exchanges queues and routing keys Exchange types x Direct exchanges x Topic exchanges Related API commands Hands on with the API e Routing Tasks Defining queues Specifying task destination Routers 2 8 1 Basics Automatic routing The simplest way to do routing is to use the CELERY_CREATE_MISSING_QUEUES setting on by default With this setting on a named queue that is not already defined in CELERY_QUEUES will be created automatically This makes it easy to perform simple routing tasks Say you have two servers x and y that handles regular tasks and one server z that only handles feed related tasks You can use this configuration CELERY_ROUTES feed tasks import_feed queue feeds With this route enabled import feed tasks will be routed to the feeds queue while all other tasks will be routed to
265. excluding verbs class Celery object def consumer_factory self BAL def Consumer self GOOD Default values Class attributes serve as default values for the instance as this means that they can be set by either instantiation or inheritance Example class Producer object active True serializer json 312 Chapter 13 Internals Celery Documeniation Release 2 5 5 def init serializer yas serializer serializer or serializer active active if active is not else active A subclass can change the default value TaskProducer Producer serializer pickle and the value can be set at instantiation gt gt gt producer TaskProducer serializer msgpack Exceptions Custom exceptions raised by an objects methods and properties should be available as an attribute and documented in the method property that throw This way a user doesn t have to find out where to import the exception from but rather use help obj and access the exception class from the instance directly Example class Empty Exception pass class Queue yes Empty Empty def get Get the next item from the queue raises Queue Empty if there are no more items left mw try return queue popleft except IndexError raise Empty Composites Similarly to exceptions composite classes should be override able by inheritance and or instantiation Common sense can be used
266. expires afte ne minute from now gt gt gt add apply_async args 10 10 expires 60 gt gt gt 38 Chapter 2 User Guide Celery Documeniation Release 2 5 5 gt gt gt from datetime import datetime timedelta gt gt gt add apply_async args 10 10 kwargs a xpires datetime now timedelta days 1 When a worker receives an expired task it will mark the task as REVOKED TaskRevokedError 2 3 4 Serializers Data transferred between clients and workers needs to be serialized The default serializer is pickle but you can change this globally or for each individual task There is built in support for pickle JSON YAML and msgpack and you can also add your own custom serializers by registering them into the Kombu serializer registry see Kombu Serialization of Data Each option has its advantages and disadvantages json JSON is supported in many programming languages is now a standard part of Python since 2 6 and is fairly fast to decode using the modern Python libraries such as cjson or simplejson The primary disadvantage to JSON is that it limits you to the following data types strings Unicode floats boolean dictionaries and lists Decimals and dates are notably missing Also binary data will be transferred using Base64 encoding which will cause the transferred data to be around 34 larger than an encoding which supports native binary types However if your data fits insid
267. f after_return args kwargs do_something MyTask after_return args kwargs 56 Chapter 2 User Guide Celery Documeniation Release 2 5 5 2 7 HTTP Callback Tasks Webhooks e Basics Enabling the HTTP task e Django webhook example e Ruby on Rails webhook example e Executing webhook tasks 2 1 Basics If you need to call into another language framework or similar you can do so by using HTTP callback tasks The HTTP callback tasks uses GET POST data to pass arguments and returns result as a JSON response The scheme to call a task is GET http example com mytask argl a arg2 b arg3 c or using POST POST http example com mytask Note POST data needs to be form encoded Whether to use GET or POST is up to you and your requirements The web page should then return a response in the following format if the execution was successful status success retval or if there was an error status failure reason Invalid moon alignment Enabling the HTTP task To enable the HTTP dispatch task you have to add celery task http to CELERY_IMPORTS or start celeryd with I celery task http 2 7 2 Django webhook example With this information you could define a simple task in Django from django http import HttpResponse from anyjson import serialize def multiply request x request GET x y request GET y
268. f enabled tasks doesn t save results or errors to the backend used celeryd now correctly handles malformed messages by throwing away and acknowledging the message instead of crashing 11 41 5 Bugs e Fixed a race condition that could happen while storing task results in the database 11 41 6 Documentation e Reference now split into two sections API reference and internal module reference 11 42 0 8 4 release date 2010 02 05 01 52 P M CEST e Now emits a warning if the detach argument is used detach should not be used anymore as it has several not easily fixed bugs related to it Instead use something like start stop daemon Supervisord or launchd os x e Make sure logger class is process aware even if running Python gt 2 6 e Error emails are not sent anymore when the task is retried 11 43 0 8 3 release date 2009 12 22 09 43 A M CEST e Fixed a possible race condition that could happen when storing querying task results using the database backend e Now has console script entry points in the setup py file so tools like Buildout will correctly install the programs celeryd and celeryinit 11 44 0 8 2 release date 2009 11 20 03 40 PM CEST e QOS Prefetch count was not applied properly as it was set for every message received which apparently behaves like receive one more instead of only set when our wanted value changed 232 Chapter 11 Change history Celery Documeniatio
269. f the worker won t shutdown after considerate time for example because of tasks stuck in an infinite loop you can use the KILL signal to force terminate the worker but be aware that currently executing tasks will be lost unless the tasks have the acks_late option set Also as processes can t override the KILL signal the worker will not be able to reap its children so make sure to do so manually This command usually does the trick ps auxww grep celeryd awk print 2 xargs kill 9 2 4 3 Restarting the worker Other than stopping then starting the worker to restart you can also restart the worker using the HUP signal kill HUP Spid The worker will then replace itself with a new instance using the same arguments as it was started with 2 4 4 Concurrency By default multiprocessing is used to perform concurrent execution of tasks but you can also use Eventlet The number of worker processes threads can be changed using the concurrency argument and defaults to the number of CPUs available on the machine Number of processes multiprocessing More worker processes are usually better but there s a cut off point where adding more processes affects performance in negative ways There is even some evidence to support that having multiple celeryd s running may perform better than having a single worker For example 3 celeryd s with 10 worker processes each You need to experiment to find the numbers that
270. fault None args kwargs 12 4 celery app defaults 257 Celery Documentation Release 2 5 5 alt None deprecate_by None remove_by None to_python value typemap bool lt function str_to_bool at 0x1cd3c80 gt string lt type str gt tuple lt type tuple gt int lt type int gt celery app defaults find args kwargs celery app defaults find_deprecated_settings source celery app defaults flatten d ns celery app defaults str_to_bool term table false False no False 1 True 0 False lt yes True true True 12 5 celery task e celery task l 12 5 1 celery task Creating tasks subtasks sets and chords copyright 3 2009 2012 by Ask Solem license BSD see LICENSE for more details celery task task args kwargs Decorator to create a task class out of any callable Examples task def refresh_feed url return Feed objects get url url refresh With setting extra options and using retry task max_retries 10 def refresh_feed url try return Feed objects get url url refresh except socket error exc refresh_feed retry exc exc Calling the resulting task gt gt gt refresh_feed http example com rss Feed http example com rss gt gt gt refresh_feed delay http example com rss syncResult 8998d0f4 da0b 4669 ba03 d5ab
271. fetch count is kept as a shared counter so as soon as consume_messages detects that the value has changed it will send out the actual QoS event to the broker Notice that when the connection is lost all internal queues are cleared because we can no longer ack the messages reserved in memory However this is not dangerous as the broker will resend them to another worker when the channel is closed WARNING stop does not close the connection This is because some pre acked messages may be in processing and they need to be finished before the channel is closed For celeryd this means the pool must finish the tasks it has acked early then close the connection celery worker consumer Component parent kwargs create w last True name consumer namespace worker class celery worker consumer Consumer ready_queue eta_schedule logger init_callback lt function noop at OxIcaf668 gt send_events False hostname None ini tial_prefetch_count 2 pool None app None pri ority_timer None controller None 328 Chapter 13 Internals Celery Documeniation Release 2 5 5 Listen for messages received from the broker and move them to the ready queue for task processing Parameters e ready_queue See ready_queue e eta_schedule See eta_schedule apply _eta_task task Method called by the timer to apply a task with an ETA countdown broadcast_consumer None The consumer used to consume broadcast co
272. for routing purposes celeryctl Now supports the inspect active_queues command 11 23 2 2 2 release date 2011 02 03 04 00 P M CET 11 23 1 Fixes Celerybeat could not read the schedule properly so entries in CELERYBEAT_SCHEDULE would not be sched uled Task error log message now includes exc_info again The eta argument can now be used with task retry Previously it was overwritten by the countdown argument celeryd multi celeryd_detach Now logs errors occuring when executing the celeryd command daemonizing cookbook Fixed typo time limit 300 gt time limit 300 Colors in logging broke non string objects in log messages setup_task_logger no longer makes assumptions about magic task kwargs 11 24 2 2 1 release date 2011 02 02 04 00 P M CET 11 24 1 Fixes e Eventlet pool was leaking memory Issue 308 e Deprecated function celery execute delay_task was accidentally removed now available again 188 Chapter 11 Change history Celery Documeniation Release 2 5 5 BasePool on_terminate stub did not exist e celeryd detach Adds readable error messages if user group name does not exist e Smarter handling of unicode decod errors when logging errors 11 25 2 2 0 release date 2011 02 01 10 00 AM CET 11 25 1 Important Notes e Carrot has been replaced with Kombu Kombu is the next generation messaging framework for Python fixing several flaws present in Carrot t
273. formance at times with bursts of tasks with a short execution time If this doesn t apply to your use case you should be able to set the prefetch multiplier to zero without sacrificing performance Note A patch to multiprocessing is currently being worked on this patch would enable us to use a better solution and is scheduled for inclusion in the 2 0 0 release celeryd now shutdowns cleanly when receiving the SIGTERM signal celeryd now does a cold shutdown if the SIGINT signal is received Ctrl C this means it tries to terminate as soon as possible Caching of results now moved to the base backend classes so no need to implement this functionality in the base classes Caches are now also limited in size so their memory usage doesn t grow out of control You can set the maximum number of results the cache can hold using the CELERY_MAX_CACHED_RESULTS setting the default is five thousand results In ad dition you can refetch already retrieved results using backend reload_task_result back end reload_taskset_result that s for those who want to send results incrementally celeryd now works on Windows again Warning If you re using Celery with Django you can t use project settings as the settings module name but the following should work S python manage py celeryd settings settings Execution messaging TaskPublisher send_task now incorporates all the functionality apply_asyn
274. g establish_connection gt app broker_connection with_connection gt app with_connection get_consumer_set gt app amqp get_task_consumer TaskPublisher gt app amqp TaskPublisher TaskConsumer gt app amqp TaskConsumer ConsumerSet gt app amqp ConsumerSet e celery conf gt app conf NOTE All configuration keys are now named the same as in the configuration So the key CEL ERY ALWAYS _EAGER is accessed as gt gt gt app conf CELERY_ALWAYS_EAGER instead of gt gt gt from celery import conf gt gt gt conf ALWAYS_EAGER get_queues gt app amqp get_queues e celery task control broadcast gt app control broadcast rate_limit gt app control rate_limit ping gt app control ping revoke gt app control revoke discard_all gt app control discard_all inspect gt app control inspect e celery utils info humanize_seconds gt celery utils timeutils humanize_seconds textindent gt celery utils textindent 13 5 The Big Instance Refactor 321 Celery Documentation Release 2 5 5 get_broker_info gt app amqp get_broker_info format_broker_info gt app amqp format_broker_info format_queues gt app amqp format_queues 13 5 5 Default App Usage To be backward compatible it must be possible to use all the classes functions
275. g newline True kill argv cmd names argv cmd node_alive pid note msg newline True restart argv cmd retcode 0 say m newline True show argv cmd shut down_nodes nodes sig 15 retry None callback None signal_node nodename pid sig splash start argv cmd stop argv cmd stop_verify argv cmd usage waitexec argv path home docs checkouts readthedocs org user_builds celery envs 2 5 archived bin python with_detacher_default_options p class celery bin celeryd_multi NamespacedOptionParser args add_option name value short False ns None optmerge ns defaults None parse 308 Chapter 12 API Reference Celery Documeniation Release 2 5 5 ce cel cel cel cel cel cel process_long_opt arg value None process_short_opt arg value None ery bin cel ery bin cel ery bin ce ery bin cel ery bin cel ery bin ce ery bin cel eryd eryd eryd eryd eryd eryd eryd m m u u u u u u u lti abbreviations map lti findsig args default 15 1lti format_opt opt value 1lti main lti multi_args p cmd celeryd append prefix suffix lti parse_ns_range ns ranges False 1ti quote v 12 38 celery bin celeryd_multi 309 Celery Documeniation Release 2 5 5 310 Chapter 12 API Reference CHAPTER 13 Internals Rel
276. g different time than UTC fixed e Windows specific Negate test for available os fork thanks miracle2k Custom carrot backends now need to include the backend class name so before where you had All AMQP settings has been renamed to BROKER_ and in addition AMQP_SERVER has been renamed to BROKER_HOST so before where you had 11 45 0 8 1 233 Celery Documentation Release 2 5 5 Now tried to handle broken PID files Added a Django test runner to contrib that sets CELERY_ALWAYS_EAGER True for testing with the database backend Added a CELERY_CACHE_BACKEND setting for using something other than the django global cache backend Use custom implementation of functools partial curry for Python 2 4 support Probably still problems with running on 2 4 but it will eventually be supported Prepare exception to pickle when saving RETRY status for all backends SQLite no concurrency limit should only be effective if the database backend is used 11 46 0 8 0 release date 2009 09 22 03 06 PM CEST 11 46 1 Backward incompatible changes e Add traceback to result value on failure Note If you use the database backend you have to re create the database table celery_taskmeta Contact the Mailing list or IRC channel for help doing this e Database tables are now only created if the database backend is used so if you change back to the database backend at some point be sure to initialize tables
277. g if running as the root user euid is 0 e celery messaging establish_connection Ability to override defaults used using keyword ar gument defaults 202 Chapter 11 Change history Celery Documeniation Release 2 5 5 celeryd Now uses multiprocessing freeze_support so that it should work with py2exe PyInstaller cx_Freeze etc celeryd Now includes more metadata for the STARTED state PID and host name of the worker that started the task See issue 181 subtask Merge additional keyword arguments to subtask into task keyword arguments e g gt gt gt s subtask 1 2 foo bar baz 1 gt gt gt s args 1 2 gt gt gt s kwargs foo bar baz 1 See issue 182 celeryd Now emits a warning if there is already a worker node using the same name running on the same virtual host AMQP result backend Sending of results are now retried if the connection is down AMQP result backend result get Wait for next state if state is not in READY_STATES TaskSetResult now supports subscription gt gt gt res TaskSet tasks apply_async gt gt gt res 0 get Added Task send_error_emails Task error_whitelist so these can be configured per task instead of just by the global setting Added Task store_errors_even_if_ignored so it can be changed per Task not just by the global setting The crontab scheduler no longer wakes up every second but implements re
278. g in process cleanup could mask task errors We no longer propagate errors happening at process cleanup but log them instead This way they will not interfere with publishing the task result Issue 365 Defining tasks did not work properly when using the Django she11_p1lus utility Issue 366 AsyncResult get did not accept the interval and propagate arguments celeryd Fixed a bug where celeryd would not shutdown if a socket error was raised 11 20 2 2 5 release date 2011 03 28 06 00 PM CEST 184 Chapter 11 Change history Celery Documeniation Release 2 5 5 11 20 1 Important Notes e Now depends on Kombu 1 0 7 11 20 2 News Our documentation is now hosted by Read The Docs http docs celeryproject org and all links have been changed to point to the new URL Logging Now supports log rotation using external tools like logrotate d Issue 321 This is accomplished by using the Wat chedFileHandl1ler which re opens the file if it is renamed or deleted Using Celery with Redis Database as the messaging queue now documents how to configure Redis Database result backends gevent Now supports ETA tasks But gevent still needs CELERY_DISABLE_RATE_LIMITS True to work TaskSet User Guide now contains TaskSet callback recipes Eventlet New signals eventlet_pool_started eventlet_pool_preshutdown eventlet_pool_postshutdown eventlet_pool_apply See celery signal
279. g on the task if any signal Name of signal to send to process if terminate Default is TERM destination If set a list of the hosts to send the command to when empty broadcast to all workers connection Custom broker connection to use if not set a connection will be established automatically connect_timeout Timeout for new connection if a custom connection is not provided reply Wait for and return the reply timeout Timeout in seconds to wait for the reply limit Limit number of replies Control time_limit task_name soft None hard None kwargs Set time limits for task by type Parameters task_name Name of task to change time limits for soft New soft time limit in seconds hard New hard time limit in seconds Any additional keyword arguments are passed on to broadcast class celery task control Inspect control destination None timeout 1 callback None active safe False active_queues add_consumer queue exchange None exchange_type direct routing_key None options cancel_consumer queue kwargs disable _ events enable_events 12 11 celery task control 275 Celery Documentation Release 2 5 5 ping registered registered_tasks reserved safe False revoked scheduled safe False stats celery task control flatten_reply reply 12 12 celery task http e celery task http j 12 12 1 celery t
280. g requests CELERY_DEFAULT_RATE_LIMIT The global default rate limit for tasks This value is used for tasks that does not have a custom rate limit The default is no rate limit CELERY_DISABLE_RATE LIMITS Disable all rate limits even if tasks has explicit rate limits set CELERY_ACKS_LATE Late ack means the task messages will be acknowledged after the task has been executed not just before which is the default behavior See also FAQ Should I use retry or acks_late 3 2 Configuration Directives 99 Celery Documeniation Release 2 5 5 3 2 16 Worker celeryd CELERY_IMPORTS A sequence of modules to import when the celery daemon starts This is used to specify the task modules to import but also to import signal handlers and additional remote control commands etc CELERYD_FORCE_EXECV On Unix the processes pool will fork so that child processes start with the same memory as the parent process This can cause problems as there is a known deadlock condition with pthread locking primitives when fork is com bined with threads You should enable this setting if you are experiencing hangs deadlocks especially in combination with time limits or having a max tasks per child limit This option will be enabled by default in a later version This is not a problem on Windows as it does not have fork CELERYD_MAX_TASKS_PER_CHILD Maximum number of tasks a pool worker process can execute before it s replaced
281. ged with 1 0 5 as the release was never announced 11 38 1 0 3 release date 2010 05 15 03 00 P M CEST 11 38 1 Important notes e Messages are now acknowledged just before the task function is executed This is the behavior we ve wanted all along but couldn t have because of limitations in the multipro cessing module The previous behavior was not good and the situation worsened with the release of 1 0 1 so this change will definitely improve reliability performance and operations in general For more information please see http bit ly Jhom6T e Database result backend result now explicitly sets null True as django picklefield version 0 1 5 changed the default behavior right under our noses See http bit ly d5OwMr This means those who created their celery tables via syncdb or celeryinit with picklefield versions gt 0 1 5 has to alter their tables to allow the result field to be NULL manually MySQL ALTER TABLE celery_taskmeta MODIFY result TEXT NULL PostgreSQL ALTER TABLE celery_taskmeta ALTER COLUMN result DROP NOT NULL e Removed Task rate_limit_queue_type as it was not really useful and made it harder to refactor some parts e Now depends on carrot gt 0 10 4 e Now depends on billiard gt 0 3 0 11 38 2 News e AMQP backend Added timeout support for result get result wait e New task option Task acks_late default CELERY_ACKS_LATE 1
282. gt connecting to amqp guest localhost 5672 gt connected 1 gt 2 8 Routing Tasks 63 Celery Documentation Release 2 5 5 Here 1 gt is the prompt The number 1 is the number of commands you have executed so far Type help for a list of commands available It also supports auto completion so you can start typing a command and then hit the tab key to show a list of possible matches Let s create a queue we can send messages to 1 gt exchange declare testexchange direct ok 2 gt queue declare testqueue ok queue testqueue messages 0 consumers 0 3 gt queue bind testqueue testexchange testkey ok This created the direct exchange testexchange and a queue named testqueue The queue is bound to the exchange using the routing key testkey From now on all messages sent to the exchange test exchange with routing key test key will be moved to this queue We can send a message by using the basic publish command 4 gt basic publish This is a message testexchange testkey ok Now that the message is sent we can retrieve it again We use the basic get command here which polls for new messages on the queue Pop a message off the queue 5 gt basic get testqueue body This is a message delivery_info delivery_tag 1 exchange u testexchange message_count 0 redelivered False routing_key u testkey properties AMQP uses ack
283. guration and defaults This document describes the configuration options available If you re using the default loader you must create the celeryconfig py module and make sure it is available on the Python path e Example configuration file e Configuration Directives Time and date settings CELERY_TIMEZONE Task settings Concurrency settings Task result backend settings Database backend settings AMQP backend settings Cache backend settings Tokyo Tyrant backend settings Redis backend settings MongoDB backend settings Cassandra backend settings Message Routing Broker Settings Task execution settings Worker celeryd Error E Mails Events Broadcast Commands Logging Security Custom Component Classes advanced Periodic Task Server celerybeat Monitor Server celerymon Deprecated Settings 3 1 Example configuration file This is an example configuration file to get you started It should contain all you need to run a basic Celery set up 87 Celery Documentation Release 2 5 5 aules CO impi wnen celery Starcs CELERY_I S myapp tasks CELERY_RESULT_BACKEND database CELERY_RESULT_DBURI sqlite mydatabase db BROKER_URL amqp guest guest localhost 5672 ELERYD_CONCURRENCY 10 Q aR Sk Se ORO ba 4 CELERY_ANNOTATIONS tasks add
284. hat was hard to fix without breaking backwards compatibility Also it adds First class support for virtual transports Redis Django ORM SQLAIchemy Beanstalk Mon goDB CouchDB and in memory Consistent error handling with introspection The ability to ensure that an operation is performed by gracefully handling connection and chan nel errors Message compression zlib bzip2 or custom compression schemes This means that ghettog is no longer needed as the functionality it provided is already available in Celery by default The virtual transports are also more feature complete with support for exchanges direct and topic The Redis transport even supports fanout exchanges so it is able to perform worker remote control commands e Magic keyword arguments pending deprecation The magic keyword arguments were responsibile for many problems and quirks notably issues with tasks and decorators and name collisions in keyword arguments for the unaware It wasn t easy to find a way to deprecate the magic keyword arguments but we think this is a solution that makes sense and it will not have any adverse effects for existing code The path to a magic keyword argument free world is the celery decorators module is deprecated and the decorators can now be found in celery task The decorators in celery task disables keyword arguments by default All examples in the documentation have been changed to use celery
285. he sum of two arguments but it will do for demonstration and it is referenced in many parts of the Celery documentation 4 1 3 Starting the worker process You can start a worker instance by using the celeryd manage command python manage py celeryd loglevel info In production you probably want to run the worker in the background as a daemon see Running Celery as a daemon For a complete listing of the command line options available use the help command python manage py help celeryd 4 1 4 Executing our task Now that the worker is running we can open up a new terminal to actually execute our task gt gt gt from celerytest tasks import add gt gt gt add delay 2 2 The delay method is a handy shortcut to the apply_async method which enables you to have greater control of the task execution To read more about executing tasks including specifying the time at which the task should execute see Executing Tasks Note Tasks need to be stored in a real module they can t be defined in the python shell or ipython bpython This is because the worker server must be able to import the task function so that it can execute it 110 Chapter 4 Django Celery Documeniation Release 2 5 5 The task should now be executed by the worker you started earlier and you can verify that by looking at the workers console output Applying a task returns an ASyncResul1t instance which can be used to check the state of the t
286. hemy Django ORM Memcached Redis AMQP MongoDB Tokyo Tyrant and Redis or you can define your own For this example we will use the amgp result backend which sends states as messages The backend is configured via the CELERY_RESULT_BACKEND option in addition individual result backends may have additional settings you can configure CELERY_RESULT_BACKEND amgp aADDITMO version rier Nigner JERY_TASK_RESULT_EXPIRES 300 H CE To read more about result backends please see Result Backends Now with the result backend configured let s execute the task again This time we ll hold on to the AsyncResult gt gt gt result add delay 4 4 Here s some examples of what you can do when you have results gt gt gt result ready returns True if the task has finished processing gt gt gt result result task is not ready so no return value None gt gt gt result get Waits until the task is done and returns the retval gt gt gt result result direct access to result doesn t re raise errors gt gt gt result successful returns True if the task didn t end in failure True If the task raises an exception the return value of result successful will be False and result result will contain the exception instance raised by the task 1 3 6 Where to go from here After this you should read the User Guide Specifically Ta
287. her argument Added CELERY_SEND_TASK_SENT_EVENT setting If enabled an event will be sent with every task so monitors can track tasks before the workers receive them celerybeat Now reuses the broker connection when applying scheduled tasks The configuration module and loader to use can now be specified on the command line For example celeryd config celeryconfig py loader myloader Loader Added signals beat_init and beat_embedded_init celery signals beat_init Dispatched when celerybeat starts either standalone or embedded Sender is the celery beat Service instance celery signals beat_embedded_init Dispatched in addition to the beat__init signal when celerybeat is started as an embedded process Sender is the celery beat Service instance Redis result backend Removed deprecated settings REDIS_TIMEOUT and REDIS_CONNECT_RETRY CentOS init script for celeryd now available in contrib centos Now depends on pyparsing version 1 5 0 or higher There have been reported issues using Celery with pyparsing 1 4 x so please upgrade to the latest version Lots of new unit tests written now with a total coverage of 95 11 25 2 2 0 195 Celery Documentation Release 2 5 5 11 25 3 Fixes e celeryev Curses Monitor Improved resize handling and UI layout Issue 274 Issue 276 e AMQP Backend Exceptions occurring while sending task results are now propagated i
288. hijack the multiprocessing logger anymore but instead use a custom logger name for different applications Application Logger Name celeryd celery celerybeat celery beat celeryev celery ev This means that the oglevel and logfile arguments will affect all registered loggers even those from 3rd party libraries Unless you configure the loggers manually as shown below that is Users can choose to configure logging by subscribing to the signal celery signals setup_logging signal from logging config import fileConfig from celery import signals signals setup_logging connect def setup_logging kwargs fileConfig logging conf If there are no receivers for this signal the logging subsystem will be configured using the logleveil logfile argument this will be used for all defined loggers Remember that celeryd also redirects stdout and stderr to the celery logger if manually configure logging you also need to redirect the stdouts manually from logging config import fileConfig from celery import log def setup_logging kwargs import logging fileConfig logging conf stdouts logging getLogger mystdoutslogger log redirect_stdouts_to_logger stdouts loglevel logging WARNING e celeryd Added command line option I include A comma separated list of task modules to be imported Example celeryd I appl tasks app2 tasks e celeryd now emits a warnin
289. ib bzip2 or any custom compression methods reg istered with kombu compression register Defaults to the CELERY_MESSAGE_COMPRESSION setting 12 6 celery task base 261 Celery Documentation Release 2 5 5 Note If the CELERY_ALWAYS_EAGER setting is set it will be replaced by a local apply call instead classmethod BaseTask delay args kwargs Star argument version of apply_async Does not support the extra options enabled by apply_async Parameters e args positional arguments passed on to the task e kwargs keyword arguments passed on to the task returns celery result AsyncResult classmethod BaseTask establish_connection connect_timeout None Establish a connection to the message broker BaseTask execute request pool loglevel logfile kwargs The method the worker calls to execute the task Parameters e request A Request e pool A task pool e loglevel Current loglevel logfile Name of the currently used logfile e consumer The Consumer classmethod BaseTask get_consumer connection None connect_timeout None Get message consumer ttype kombu messaging Consumer Warning If you don t specify a connection one will automatically be established for you in that case you need to close this connection after use gt gt gt consumer get_consumer gt gt gt gt gt gt consumer cl
290. ibute and in the body of the task just call the process_clicks function we wrote earlier 8 3 6 Finishing There are still ways to improve this application The URLs could be cleaned so the URL http google com and http google com is the same Maybe it s even possible to update the click count using a single UPDATE query If you have any questions regarding this tutorial please send a mail to the mailing list or come join us in the celery IRC channel at Freenode http celeryq org introduction html getting help 148 Chapier 8 Tutorials CHAPTER 9 Frequently Asked Questions 149 Celery Documentation Release 2 5 5 e General What kinds of things should I use Celery for Misconceptions Is Celery dependent on pickle Is Celery for Django only Do I have to use AMQP RabbitMQ Is Celery multilingual e Troubleshooting MySQL is throwing deadlock errors what can I do celeryd is not doing anything just hanging Task results aren t reliably returning Why is Task delay apply celeryd just hanging Does it work on FreeBSD I m having IntegrityError Duplicate Key errors Why Why aren t my tasks processed Why won t my Task run Why won t my periodic task run How do I discard all waiting tasks I ve discarded messages but there are still messages left in the queue e Results How do I get the result of a task if I have the ID that poin
291. ic init scripts for celerybeat and celeryev has been added 11 16 2 News e Automatic connection pool support The pool is used by everything that requires a broker connection For example applying tasks sending broadcast commands retrieving results with the AMQP result backend and so on The pool is disabled by default but you can enable it by configuring the BROKER_POOL_LIMIT setting BROKER_POOL_LIMIT 10 A limit of 10 means a maximum of 10 simultaneous connections can co exist Only a single con nection will ever be used in a single thread environment but in a concurrent environment threads greenlets etc but not processes when the limit has been exceeded any try to acquire a connec tion will block the thread and wait for a connection to be released This is something to take into consideration when choosing a limit A limit of None or 0 means no limit and connections will be established and closed every time e Introducing Chords taskset callbacks A chord is a task that only executes after all of the tasks in a taskset has finished executing It s a fancy term for taskset callbacks adopted from Cw It works with all result backends but the best implementation is currently provided by the Redis result backend Here s an example chord gt gt gt chord add subtask i i for i in 100 tsum subtask get Please read the Chords section in the user guide if you want to know more
292. icate tasks Using a centralized approach means the schedule does not have to be synchronized and the service can operate without using locks 2 5 2 Entries To schedule a task periodically you have to add an entry to the CELERYBEAT_SCHEDULE setting Example Run the tasks add task every 30 seconds from datetime import timedelta CELERYBEAT_SCHEDULE runs every 30 seconds mask tasks add schedule timedelta seconds 30 targa 16 16 hy Using a t imedelta for the schedule means the task will be executed 30 seconds after celerybeat starts and then every 30 seconds after the last run A crontab like schedule also exists see the section on Crontab schedules Available Fields e task The name of the task to execute e schedule The frequency of execution This can be the number of seconds as an integer at imedelta ora crontab You can also define your own custom schedule types by extending the interface of schedule 50 Chapter 2 User Guide Celery Documeniation Release 2 5 5 e args Positional arguments list or tuple e kwargs Keyword arguments dict options Execution options dict This can be any argument supported by apply_async e g exchange routing_key expires and so on e relative By default timedelta schedules are scheduled by the clock This means the frequency is rounded to the nearest second minute hou
293. id None Applies the taskset locally by blocking until all tasks return apply async connection None connect_timeout None publisher None taskset_id None Apply taskset tasks total None Total number of subtasks in this set celery task sets group alias of TaskSet celery task sets maybe_subtask t class celery task sets subtask fask None args None kwargs None options None ex Class that wraps the arguments and execution options for a single task invocation Used as the parts ina TaskSet or to safely pass tasks around as callbacks Parameters e task Either a task class instance or the name of a task e args Positional arguments to apply 266 Chapter 12 API Reference Celery Documeniation Release 2 5 5 e kwargs Keyword arguments to apply e options Additional options to Task apply_async Note that if the first argument is a dict the other arguments will be ignored and the values in the dict will be used instead gt gt gt s subtask tasks add args 2 2 gt gt gt subtask s task tasks add args 2 2 kwargs options apply args kwargs options Apply this task locally apply_async args kwargs options Apply this task asynchronously clone args kwargs options delay argmerge kwmerge Shortcut to apply_async argmerge kwargs type 12 8 celery task chords e celery task chords j 12 8 1 celery task
294. ilter runs in the background so the user doesn t have to wait for it to finish We have a Django blog application allowing comments on blog posts We ll describe parts of the models views and tasks for this application blog models py The comment model looks like this from django db import models from django utils translation import ugettext_lazy as _ 2 2 Tasks 35 Celery Documentation Release 2 5 5 class Comment models Model name models CharField _ name max_length 64 email_address models EmailField _ email address homepage models URLField _ home page blank True verify_exists Fa comment models TextField _ comment pub_date models DateTimeField _ Published date editable auto_add_now T1 is_spam models BooleanField _ spam default False editable class Meta verbose_name _ comment verbose_name_plural _ comments In the view where the comment is posted we first write the comment to the database then we launch the spam filter task in the background blog views py from django import forms from django http import HttpResponseRedirect from django template context import RequestContext from django shortcuts import get_object_or_404 render_to_respons from blog import tasks from blog models import Comment class CommentForm forms ModelForm class Meta model Comment def add_comment request slug template_name comments create ht
295. ime 3 01s eta 2010 06 04T10 02 21 513155 args 3 result 3 kwargs Workers online casper local Info events 43 tasks 2 workers 1 1 Keys j up k down i info t traceback r result c revoke c quit 214 Chapter 11 Change history Celery Documeniation Release 2 5 5 If you run celeryev with the d switch it will act as an event dumper simply dumping the events it receives to standard out celeryev d gt celeryev starting capture casper local 2010 06 04 10 42 07 020000 heartbeat casper local 2010 06 04 10 42 14 750000 task received tasks add 61a68756 27f4 4879 b816 3cf815672b0e args 2 2 kwargs eta 2010 06 04T10 42 16 669290 retries 0 casper local 2010 06 04 10 42 17 230000 task started tasks add 61a68756 27f4 4879 b816 3cf815672b0e args 2 2 kwargs casper local 2010 06 04 10 42 17 960000 task succeeded tasks add 61a68756 27f4 4879 b816 3cf815672b0e args 2 2 kwargs result 4 runtime 0 782663106918 The fields here are in order sender hostname xtimestamp x xevent type and xadditional event fields AMQP result backend Now supports ready successful result status and even responds to changes in task state New user guides Workers Guide Sets of tasks Subtasks and Callbacks Routing Tasks billiard has been moved back to the celery repository celeryd Standard out error is now being redirected to the log fil
296. imeUUID type as a comparator create column family task_results with comparator TimeUUIDType Example configuration CASSANDRA_SERVERS localhost 9160 CASSANDRA_KEYSPACE celery CASSANDRA_COLUMN_FAMILY task results CASSANDRA_READ_CONSISTENCY ONE CASSANDRA_WRITE_CONSISTENCY ONE CASSANDRA_DETAILED MODE Trui 3 2 13 Message Routing CELERY_QUEUES The mapping of queues the worker consumes from This is a dictionary of queue name options See Routing Tasks for more information The default is a queue exchange binding key of celery with exchange type direct You don t have to care about this unless you want custom routing facilities 94 Chapter 3 Configuration and defaults Celery Documeniation Release 2 5 5 CELERY_ROUTES A list of routers or a single router used to route tasks to queues When deciding the final destination of a task the routers are consulted in order See Routers for more information CELERY_CREATE_MISSING_QUEUES If enabled default any queues specified that is not defined in CELERY_QUEUES will be automatically created See Automatic routing CELERY_DEFAULT_QUEUE The queue used by default if no custom queue is specified This queue must be listed in CELERY_QUEUES The default is celery See also Changing the name of the default queue CELERY_DEFAULT_EXCHANGE Name of the default ex
297. implementation of this writing the snapshots to a database in djcelery snapshots in the django celery distribution copyright 3 2009 2012 by Ask Solem license BSD see LICENSE for more details class celery events snapshot Polaroid state freq 1 0 maxrate None cleanup_freq 3600 0 logger None timer None app None cancel capture cleanup cleanup_signal lt Signal Signal gt clear_after False install on_cleanup on_shutter state shutter shutter_signal lt Signal Signal gt timer lt module celery utils timer2 from celery utils timer2 pyc gt celery events snapshot eveam camera freq 1 0 maxrate None loglevel 0 logfile None pid file None timer None app None 13 6 40 celery events cursesmon s celery events cursesmon j celery events cursesmon Graphical monitor of Celery events using curses copyright 3 2009 2012 by Ask Solem license BSD see LICENSE for more details class celery events cursesmon CursesMonitor state keymap None app None alert callback title None alert_remote_control_reply reply background 7 13 6 Internal Module Reference 373 Celery Documentation Release 2 5 5 display height display_task_row lineno task display width draw find_position foreground 0 format_row uuid task worker timestamp state greet celeryev 2 5 5 handle_keypress help j up k down i info t tracebac
298. import deque from Queue import Queue Empty from datastructures import TokenBucket from utils import timeutils from utils compat import izip_longest chain_from_iterable e Wildcard imports must not be used from xxx import 128 Chapter 6 Contributing Celery Documeniation Release 2 5 5 e For distributions where Python 2 5 is the oldest support version additional rules apply Absolute imports must be enabled at the top of every module from future _ import absolute_import If the module uses the with statement it must also enable that from __future__ import with_statement Every future import must be on its own line as older Python 2 5 releases did not support import ing multiple features on the same future import line from future _ import absolute_import from future __ import with_statement from future __ import absolute_import with_statement Note that this rule does not apply if the package does not include support for Python 2 5 e Note that we use new style relative imports when the distribution does not support Python versions below 2 5 from import submodule 6 8 Contacts This is a list of people that can be contacted for questions regarding the official git repositories PyPI packages Read the Docs pages If the issue is not an emergency then it is better to report an issue 6 8 1 Committers Ask Solem github https github com ask twitter http twitter com asksol Mher
299. in requirements pkgutils txt Installing the dependencies pip E SVIRTUAL_ENV install U r requirements pkgutils txt 126 Chapter 6 Contributing Celery Documeniation Release 2 5 5 pyflakes amp PEP8 amp To ensure that your changes conform to PEP8 and to run pyflakes execute paver flakes To not return a negative exit code when this command fails use the E option this can be convenient while developing paver flake8 E API reference To make sure that all modules have a corresponding section in the API reference please execute paver autodoc paver verifyindex If files are missing you can add them by copying an existing reference file If the module is internal it should be part of the internal reference located in docs internals reference If the module is public it should be located in docs reference For example if reference is missing for the module celery worker awesome and this module is considered part of the public API use the following steps cd docs reference S cp celery schedules rst celery worker awesome rst vim celery worker awesome rst VN change every occurance of celery worker awesome celery schedules to vim index rst Add celery worker awesome to the index Add the file to git git add celery worker awesome rst git add index rst git commit celery worker awesome rst index rst m Adds reference for celery work
300. in times when there s a lot of work to do z celeryd Q feed_tasks default hostname z example com If you have another queue but on another exchange you want to add just specify a custom exchange and exchange type CELERY_QUEUES feed_tasks binding_key feed regular_tasks binding_key task image_tasks binding_key image compress exchange mediatasks exchange_type direct bs If you re confused about these terms you should read up on AMQP See also In addition to the AMQP Primer below there s Rabbits and Warrens an excellent blog post describing queues and exchanges There s also AMQP in 10 minutes Flexible Routing Model and Standard Exchange Types For users of RabbitMQ the RabbitMQ FAQ could be useful as a source of information 2 8 2 AMQP Primer Messages A message consists of headers and a body Celery uses headers to store the content type of the message and its content encoding The content type is usually the serialization format used to serialize the message The body contains the name of the task to execute the task id UUID the arguments to execute it with and some additional metadata like the number of retries or an ETA This is an example task message represented as a Python dictionary task myapp tasks add id 54086c5e 6193 4575 8308 dbab76798756 args 4 4 kwargs Producers co
301. ine argv namespace celery Read configuration from argv The config task args options Decorator to create a task class out of any callable Examples task def refresh_feed url return Feed objects get url url refresh with setting extra options and using retry from celery task import current task exchange feeds def refresh_feed url try return Feed objects get url url refresh except socket error exc current retry exc exc 246 Chapter 12 API Reference Celery Documeniation Release 2 5 5 Calling the resulting task gt gt gt refresh_feed http example com rss Feed http example com rss gt gt gt refresh_feed delay http example com rss AsyncResult I8d0 4 da0b 4669 ba03 d5ab5ac6ad5d gt create _task_cls Creates a base task class using default configuration taken from this app TaskSet args kwargs Create new TaskSet send_task name args None kwargs None countdown None eta None task_id None pub lisher None connection None connect_timeout None result_cls None expires None queues None options Send task by name Parameters e name Name of task to execute e g tasks add e result_cls Specify custom result class Default is using AsyncResult Supports the same arguments as apply_async AsyncResult task_id backend None task_name None Create celery result BaseAsyncResult instance
302. ing access to memory contents can be done by launching every task in a subprocess fork execve Limiting file system and device access can be accomplished by using chroot jail sandboxing virtual machines or other mechanisms as enabled by the platform or additional software Note also that any task executed in the worker will have the same network access as the machine on which it s running If the worker is located on an internal network it s recommended to add firewall rules for outbound traffic 2 10 3 Serializers The default pickle serializer is convenient because it supports arbitrary Python objects whereas other serializers only work with a restricted set of types But for the same reasons the pickle serializer is inherently insecure _ and should be avoided whenever clients are untrusted or unauthenticated Celery comes with a special auth serializer that validates communication between Celery clients and workers making sure that messages originates from trusted sources Using Public key cryptography the auth serializer can verify the authenticity of senders to enable this read Message Signing for more information 76 Chapter 2 User Guide Celery Documeniation Release 2 5 5 2 10 4 Message Signing Celery can use the pyOpenSSL library to sign message using Public key cryptography where messages sent by clients are signed using a private key and then later verified by the worker using a public certificate
303. ing quite stable with a lot of new features so bump version to 0 2 This is a pre release e celery task mark_as_read and celery task mark_as_failure has been removed Use cel ery backends default_backend mark_as_read and celery backends default_backend mark_as_failure instead 11 60 0 1 15 release date 2009 05 19 04 13 P M CET e The celery daemon was leaking AMQP connections this should be fixed if you have any problems with too many files open like emfile errors in rabbit log please contact us 11 61 0 1 14 release date 2009 05 19 01 08 P M CET e Fixed a syntax error in the TaskSet class No such variable TimeOutError 11 62 0 1 13 release date 2009 05 19 12 36 PM CET e Forgot to add yadayada to install requirements e Now deletes all expired task results not just those marked as done 11 57 0 2 0 pre3 241 Celery Documeniation Release 2 5 5 e Able to load the Tokyo Tyrant backend class without django configuration can specify tyrant settings directly in the class constructor e Improved API documentation e Now using the Sphinx documentation system you can build the html documentation by doing S cd docs make html and the result will be in docs build html 11 63 0 1 12 release date 2009 05 18 04 38 P M CET delay_task etc now returns celery task AsyncResult object which lets you check the result and any failure that might have happened It kind of works like the multiprocessing
304. inspect Inspects a running worker Examples Inspect a single worker gt gt gt 1 inspect myworker example com Inspect several workers gt gt gt i inspect myworker example com myworker2 example com 208 Chapter 11 Change history Celery Documeniation Release 2 5 5 Inspect all workers consuming on this vhost gt gt gt 1 inspect Methods Get currently executing tasks gt gt gt i active Get currently reserved tasks gt gt gt i reserved Get the current eta schedul gt gt gt i scheduled Worker statistics and info gt gt gt i stats List of currently revoked tasks gt gt gt i revoked List of registered tasks gt gt gt L registered_tasks e Remote control commands dump_active dump_reserved dump_schedule now replies with detailed task requests Containing the original arguments and fields of the task requested In addition the remote control command set_loglevel has been added this only changes the log level for the main process e Worker control command execution now catches errors and returns their string representation in the reply e Functional test suite added celery tests functional case contains utilities to start and stop an embedded celeryd process for use in functional testing 11 33 2 0 1 release date 2010 07 09 03 02 P M CEST e multiprocessing pool Now handles encoding errors so that pickling errors doesn
305. ints warning on missing celeryconfig py instead of raising ImportError celeryd raises ImproperlyConfigured if the configuration is not set up This makes it possible to use help etc without having a working configuration Also this makes it possible to use the client side of celery without being configured gt gt gt from carrot connection import BrokerConnection gt gt gt conn BrokerConnection localhost guest guest gt gt gt from celery execute import send_task gt gt gt r send_task celery ping args kwargs connection conn gt gt gt from celery backends amqp import AMOPBackend gt gt gt r backend AMOPBackend connection conn gt gt gt r get pong e The following deprecated settings has been removed as scheduled by the deprecation timeline Setting name Replace with CELERY_AMQP_CONSUMER_QUEUES CELERY_QUEUES CELERY_AMQP_EXCHANGE CELERY_AMQP_EXCHANGE_TYPE CELERY_AMQP_CONSUMER_ROUTING_KEY CELERY_QUEUES CELERY_AMQP_PUBLISHER_ROUTING_KEY CELERY_DEFAULT_ROUTING_KEY CELERY_DEFAULT_EXCHANGE CELERY_DEFAULT_EXCHANGE_TYPE e The celery task rest module has been removed use celery task http instead as scheduled by the depre cation timeline e It s no longer allowed to skip the class name in loader names as scheduled by the deprecation timeline CEL Assuming the implicit Loader class name is no longer supported if you use e g
306. ion Fix contributed by Martin Melin e Fixed 2 5 compatibility issue with imports Fix contributed by Iurii Kriachko e All programs now fix up___package__ when called as main This fixes compatibility with Python 2 5 Fix contributed by Martin Melin e celeryctl can now be configured on the command line Like with celeryd it is now possible to configure celery settings on the command line for celeryctl celeryctl broker pool_limit 30 e Version dependency for python dateutil fixed to be strict Fix contributed by Thomas Meson e Task __call__ is now optimized away in the task tracer rather than when the task class is created This fixes a bug where a custom __call__ may mysteriously disappear e Autoreload s inotify support has been improved Contributed by Mher Movsisyan e The Django broker documentation has been improved 172 Chapter 11 Change history Celery Documeniation Release 2 5 5 e Removed confusing warning at top of routing user guide 11 4 2 5 1 release date 2012 03 01 01 00 P M GMT by Ask Solem 11 4 1 Fixes Eventlet Gevent A small typo caused celeryd to hang when eventlet gevent was used this was because the environment was not monkey patched early enough Eventlet Gevent Another small typo caused the mediator to be started with eventlet gevent which would make celeryd sometimes hang at shutdown Mulitprocessing Fixed an error occurring if the pool was stopped before it was properly s
307. ion This is an example configuration for those using django celery etc default celerybeat here the Django project is CELERYBEAT_CHDIR opt Project Name of the projects settings module export DJANGO_SETTINGS_MODULE settings Path to celerybeat CELERYBEAT opt Project manage py celerybeat Extra arguments to celerybeat CELERYBEAT_OPTS schedule var run celerybeat schedule Available options e CELERYBEAT_OPTS Additional arguments to celerybeat see celerybeat help for a list e CELERYBEAT_PIDFILE Full path to the PID file Default is var run celeryd pid 5 2 Running celeryd as a daemon 117 Celery Documentation Release 2 5 5 e CELERYBEAT_LOGFILE Full path to the celeryd log file Default is var log celeryd log e CELERYBEAT_LOG_LEVEL Log level to use for celeryd Default is INFO e CELERYBEAT Path to the celeryd program Default is celeryd You can point this to an virtualenv or even use manage py for django e CELERYBEAT_USER User to run celeryd as Default is current user e CELERYBEAT_GROUP Group to run celeryd as Default is current user Troubleshooting If you can t get the init scripts to work you should try running them in verbose mode sh x etc init d celeryd start This can reveal hints as to why the service won t start Also you will see the commands generated so you can try to run the celeryd command ma
308. is done 6 6 Working on Features amp Patches 125 Celery Documentation Release 2 5 5 You can also attach pull requests to existing issues by following the steps outlined here http bit ly koJoso Calculating test coverage Code coverage in HTML nosetests with coverage3 cover3 html The coverage output will then be located at celery tests cover index html Code coverage in XML Cobertura style nosetests with coverage3 cover3 xml cover3 xml file coverage xml The coverage XML output will then be located at coverage xml Running the tests on all supported Python versions There is a tox configuration file in the top directory of the distribution To run the tests for all supported Python versions simply execute tox If you only want to test specific Python versions use the e option tox e py25 py26 6 6 4 Building the documentation To build the documentation you need to install the dependencies listed in requirements docs txt pip E SVIRTUAL_ENV install U r requirements docs txt After these dependencies are installed you should be able to build the docs by running S cd docs S rm rf build make html Make sure there are no errors or warnings in the build output After building succeeds the documentation is available at build html 6 6 5 Verifying your contribution To use these tools you need to install a few dependencies These dependencies can be found
309. isses documentation and tests so anyone interested is encouraged to improve this situation e celeryd now survives a restart of the AMQP server Automatically re establish AMQP broker connection if it s lost New settings AMQP_CONNECTION_RETRY Set to True to enable connection retries AMQP_CONNECTION_MAX_RETRIES Maximum number of restarts before we give up Default 100 11 46 3 News e Fix an incompatibility between python daemon and multiprocessing which resulted in the Errno 10 No child processes problem when detaching e Fixed a possible DjangoUnicodeDecodeError being raised when saving pickled data to Django s mem cached cache backend e Better Windows compatibility e New version of the pickled field taken from http www djangosnippets org snippets 5 13 e New signals introduced task_sent task_prerun and task_postrun see celery signals for more infor mation e TaskSetResult join caused TypeError when timeout None Thanks Jerzy Kozera Closes 31 e views apply should return HttpResponse instance Thanks to Jerzy Kozera Closes 32 PeriodicTask Save conversion of run_every from int to timedelta to the class attribute instead of on the in stance e Exceptions has been moved to celery exceptions but are still available in the previous module e Try to rollback transaction and retry saving result if an error happens while setting task status with the database backend e jail refactored into ce
310. ity 10 Timer next Timer on_tick None Timer queue Timer run Timer running False Timer stop celery utils timer2 to_timestamp d 13 6 54 celery utils dispatch 13 6 55 celery utils dispatch signal Signal class 386 Chapter 13 Internals Celery Documeniation Release 2 5 5 class celery utils dispatch signal Signal providing_args None Base class for all signals receivers Internal attribute holds a dictionary of receriverkey id weakref receiver mappings connect args kwargs Connect receiver to sender for signal Parameters e receiver A function or an instance method which is to receive signals Re ceivers must be hashable objects if weak is True then receiver must be weak referencable more precisely saferef safe_ref must be able to create a reference to the receiver Receivers must be able to accept keyword arguments If receivers have a dispatch_uid attribute the receiver will not be added if another receiver already exists with that dispatch_uid sender The sender to which the receiver should respond Must either be of type Signal or None to receive events from any sender e weak Whether to use weak references to the receiver By default the module will attempt to use weak references to the receiver objects If this parameter is false then strong references will be used e dispatch_uid An identifier used to uniquely identify a particular inst
311. j k get key default None items iteritems setdefault key default ConfigurationView class celery datastructures ConfigurationView changes defaults A view over an applications configuration dicts If the key does not exist in changes the defaults dict is consulted Parameters e changes Dict containing changes to the configuration e defaults Dict containing the default configuration changes None defaults None get key default None items iteritems iterkeys itervalues keys setdefault key default update args kwargs values ExceptionInfo class celery datastructures ExceptionInfo exc_info internal False Exception wrapping an exception and its traceback Parameters exc_info The exception info tuple as returned by sys exc_info exception None Exception instance internal False Set to true if this is an internal error tb None Pickleable traceback instance for use with t raceback traceback None String representation of the traceback 13 6 Internal Module Reference 369 Celery Documentation Release 2 5 5 type None Exception type LimitedSet class celery datastructures LimitedSet maxlen None expires None Kind of Set with limitations Good for when you need to test for membership a in set but the list might become to big so you want to limit it so it doesn t consume too much resources Parameters e maxlen Maximum nu
312. ject weak_func weak reference to the target function _all_instances class attribute pointing to all live BoundMethodWeakref objects indexed by the class s calcu late_key target method applied to the target objects This weak value dictionary is used to short circuit creation so that multiple references to the same object function pair produce the same BoundMethod Weakref instance classmethod calculate_key target Calculate the reference key for this reference Currently this is a two tuple of the id s of the target object and the target function respectively class celery utils dispatch saferef BoundNonDescriptorMethodWeakref target on_delete None A specialized BoundMethodWeakref for platforms where instance methods are not descriptors It assumes that the function name and the target attribute name are the same instead of assuming that the function is a descriptor This approach is equally fast but not 100 reliable because functions can be stored on an attribute named differenty than the function s name such as in gt gt gt class A yi pass gt gt gt def foo Ja ae return foo gt gt gt A bar foo But this shouldn t be a common use case So on platforms where methods aren t descriptors such as Jython this implementation has the advantage of working in the most cases 388 Chapter 13 Internals Celery Documeniation Release 2 5 5 celery utils dispatch saferef get_bound_method
313. k r result c revoke c quit help _title Keys info_str Info init_screen keyalias 258 J 259 K 343 T keymap limit move_selection direction 1 move_selection_down move_selection_up nap online_str Workers online readline x y resetscreen revoke_selection safe_add_str y x string args kwargs screen_delay 10 screen_height screen_width selected_position 0 selected_str Selected selected_task None selection_info selection_rate_limit selection_result selection_traceback tasks 374 Chapter 13 Internals Celery Documeniation Release 2 5 5 win None workers class celery events cursesmon DisplayThread display run celery events cursesmon capture_events app state display celery events cursesmon evtop app None 13 6 41 celery events dumper e celery events dumper j celery events dumper THis is a simple program that dumps events to the console as they happen Think of it like a tcpdump for Celery events copyright 3 2009 2012 by Ask Solem license BSD see LICENSE for more details class celery events dumper Dumper format_task_event hostname timestamp type task event on_event event celery events dumper evdump app None celery events dumper humanize_type type 13 6 42 celery db models class celery db model1s Task task_id Task result status
314. l but needed if your MongoDB server requires authentication Results If you also want to store the state and return values of tasks in MongoDB you should see MongoDB backend settings Limitations The mongodb message transport currently does not support e Remote control commands celeryctl broadcast 1 2 6 Using CouchDB Installation For the CouchDB support you have to install additional dependencies You can install both Celery and these depen dencies in one go using either the celery with couchdb or the django celery with couchdb bundles pip install U celery with couchdb Configuration Configuration is easy set the transport and configure the location of your CouchDB database BROKER_URL couchdb localhost 5984 database_name Where the URL is in the format of couchdb userid password hostname port database_name The host name will default to Localhost and the port to 5984 and so they are optional userid and password are also optional but needed if your CouchDB server requires authentication Results Storing task state and results in CouchDB is currently not supported 1 2 Brokers 11 Celery Documentation Release 2 5 5 Limitations The Beanstalk message transport does not currently support e Remote control commands celeryctl broadcast 1 2 7 Using Beanstalk Installation For the Beanstalk support you have to install additional dependencies You can install both Celery
315. lared Defaults to the exchange_type attribute e immediate Request immediate delivery Will raise an exception if the task cannot be routed to a worker immediately Do not confuse this parameter with the countdown and eta settings as they are unrelated Defaults to the immediate attribute e mandatory Mandatory routing Raises an exception if there s no running workers able to take on this task Defaults to the mandatory attribute e priority The task priority a number between 0 and 9 Defaults to the priority attribute e serializer A string identifying the default serialization method to use Can be pickle json yaml msgpack or any custom serialization method that has been registered with kombu serialization registry Defaults to the serializer attribute e compression A string identifying the compression method to use Can be one of zlib bzip2 or any custom compression methods reg istered with kombu compression register Defaults to the CELERY_MESSAGE_COMPRESSION setting Note If the CELERY_ALWAYS_EAGER setting is set it will be replaced by a local apply call instead BaseTask autoregister True If disabled this task won t be registered automatically BaseTask backend None The result store backend used for this task BaseTask default_retry delay 180 Default time in seconds before a retry of the task should be executed 3 minutes by defaul
316. le memory leak it can result in e The ETA scheduler now sleeps at most two seconds between iterations e The ETA scheduler now deletes any revoked tasks it might encounter As revokes are not yet persistent this is done to make sure the task is revoked even though it s currently being hold because its eta is e g a week into the future e The task_id argument is now respected even if the task is executed eagerly either using apply or CELERY_ALWAYS_EAGER e The internal queues are now cleared if the connection is reset e New magic keyword argument delivery_info Used by retry to resend the task to its original destination using the same exchange routing_key e Events Fields was not passed by send fixes the UUID key errors in celerymon Added schedule s option to celeryd so it is possible to specify a custom schedule filename when using an embedded celerybeat server the B beat option e Better Python 2 4 compatibility The test suite now passes e task decorators Now preserve docstring as cls __doc__ was previously copied to cls run __doc__ e The testproj directory has been renamed to fests and we re now using nose django nose for test discovery and unittest2 for test cases e New pip requirements files available in contrib requirements TaskPublisher Declarations are now done once per process 11 40 1 0 1 227 Celery Documeniation Release 2 5 5 e Added Task deli
317. len QUEUE_NAME The default queue is named celery To get all available queues invoke 72 Chapter 2 User Guide Celery Documeniation Release 2 5 5 redis cli h HOST p PORT n DATABASE_NUMBER keys Note If a list has no elements in Redis it doesn t exist Hence it won t show up in the keys command output llen for that list returns 0 in that case On the other hand if you re also using Redis for other purposes the output of the keys command will include unrelated values stored in the database The recommended way around this is to use a dedicated DATABASE_NUMBER for Celery 2 9 5 Munin This is a list of known Munin plug ins that can be useful when maintaining a Celery cluster e rabbitmq munin Munin plug ins for RabbitMQ http github com ask rabbitmq munin e celery_tasks Monitors the number of times each task type has been executed requires celerymon http exchange munin monitoring org plugins celery_tasks 2 details e celery_task_states Monitors the number of tasks in each state requires celerymon http exchange munin monitoring org plugins celery_tasks details 2 9 6 Events The worker has the ability to send a message whenever some event happens These events are then captured by tools like celerymon and celeryev to monitor the cluster Snapshots New in version 2 1 Even a single worker can produce a huge amount of events so storing the history of all e
318. ler for the tasks with an ETA This means waiting eta tasks are sorted by time so we don t have to poll the whole list all the time e Now also imports modules listed in CELERY_IMPORTS when running with django as documented e Log level for stdout stderr changed from INFO to ERROR e ImportErrors are now properly propagated when autodiscovering tasks e You can now use celery messaging establish_connection to establish a connection to the broker e When running as a separate service the periodic task scheduler does some smart moves to not poll too regularly If you need faster poll times you can lower the value of CELERYBEAT_MAX_LOOP_INTERVAL e You can now change periodic task intervals at runtime by making run_every a property or subclassing Period icTask is_due 11 41 1 0 0 231 Celery Documeniation Release 2 5 5 The worker now supports control commands enabled through the use of a broadcast queue you can remotely revoke tasks or set the rate limit for a task type See celery task control The services now sets informative process names as shown in ps listings if the setproctitle module is installed celery exceptions NotRegistered now inherits from KeyError and TaskReg istry __getitem__ pop raises NotRegistered instead You can set the loader via the CELERY_ LOADER environment variable You can now set CELERY_IGNORE_RESULT to ignore task results by default i
319. lery utils mail Message to None sender None subject None body None charset us ascii exception celery utils mail SendmailWarning Problem happened while sending the email message 12 17 celery exceptions e celery exceptions j 12 17 1 celery exceptions This module contains Celery specific exceptions copyright 3 license exception ce 2009 2012 by Ask Solem BSD see LICENSE for more details lery exceptions AlreadyRegistered The task is already registered exception ce lery exceptions AlwaysEagerIgnored send_task ignores CELERY_ALWAYS_EAGER option exception ce exception ce exception ce lery exceptions CDeprecationWarning lery exceptions CPendingDeprecationWarning lery exceptions ImproperlyConfigured Celery is somehow improperly configured exception ce lery exceptions InvalidTaskError The task has invalid data or is not properly constructed exception ce lery exceptions MaxRetriesExceededError The tasks max restart limit has been exceeded exception ce lery exceptions NotConfigured Celery has not been configured as no config module has been found exception ce lery exceptions NotRegistered The task is not registered exception ce lery exceptions QueueNotFound Task routed to a queue not in CELERY_QUEUES exception ce lery exceptions RetryTaskError message exc args kwargs The task is to be retried later exception c
320. lery actors 273 Celery Documentation Release 2 5 5 type direct Control broadcast command arguments None destination None connection None con nect_timeout None reply False timeout 1 limit None callback None channel None Broadcast a control command to the celery workers Parameters e command Name of command to send e arguments Keyword arguments for the command e destination If set a list of the hosts to send the command to when empty broadcast to all workers connection Custom broker connection to use if not set a connection will be established automatically connect_timeout Timeout for new connection if a custom connection is not provided e reply Wait for and return the reply e timeout Timeout in seconds to wait for the reply e limit Limit number of replies e callback Callback called immediately for each reply received Control discard_all connection None connect_timeout None Discard all waiting tasks This will ignore all tasks waiting for execution and they will be deleted from the messaging server Returns the number of tasks discarded Control inspect destination None timeout 1 callback None Control ping destination None timeout 1 kwargs Ping workers Returns answer from alive workers Parameters e destination If set a list of the hosts to send the command to when empty broadcast to all workers connection Custom b
321. lery execute ExecuteWrapper e views apply now correctly sets mime type to application json e views task_status now returns exception if state is RETRY e views task_status now returns traceback if state is FAILURE or RETRY e Documented default task arguments e Add a sensible __repr__ to ExceptionInfo for easier debugging 11 46 0 8 0 235 Celery Documentation Release 2 5 5 Fix documentation typo import map gt import dmap Thanks to mikedizon 11 47 0 6 0 release date 2009 08 07 06 54 A M CET 11 47 1 Important changes Fixed a bug where tasks raising unpickleable exceptions crashed pool workers So if you ve had pool workers mysteriously disappearing or problems with celeryd stopping working this has been fixed in this version Fixed a race condition with periodic tasks The task pool is now supervised so if a pool worker crashes goes away or stops responding it is automati cally replaced with a new one Task name is now automatically generated out of class module name e g djangotwitter tasks UpdateStatusesTask Very convenient No idea why we didn t do this before Some documentation is updated to not manually specify a task name 11 47 2 News Tested with Django 1 1 New Tutorial Creating a click counter using carrot and celery Database entries for periodic tasks are now created at celeryd startup instead of for each check which has been a forgotten TODO XXX in the code
322. lerybeat schedule Beat logfile None Beat loglevel None Beat redirect_stdouts None Beat redirect_stdouts_level None Beat run Beat schedule None Beat scheduler_cls None Beat set_process_title Beat setup_logging Beat start_scheduler logger None Beat startup_info beat 298 Chapter 12 API Reference Celery Documeniation Release 2 5 5 12 32 celery bin base class celery bin base Command app None get_app None Base class for command line applications Parameters e app The current app e get_app Callable returning the current app if no app provided Parser alias of OptionParser args Arg list used in help create_parser prog_name enable_config_from_cmdline False Enable if the application should support config from the cmdline execute_from_ commandline argv None Execute application from command line Parameters argv The list of command line arguments Defaults to sys argv expanduser value get_cls_by_name name get_options Get supported command line options handle_argv prog_name argv Parses command line arguments from argv and dispatches to run Parameters e prog_name The program name argv 0 e argy Command arguments Exits with an error message if supports_args is disabled and argv contains positional arguments namespace celery Default configuration namespace option_list List of options
323. ll of the tasks in the header has returned Each step in the header is executed as a task in parallel possibly on different nodes The callback is then applied with the return value of each task in the header The task id returned by chord is the id of the callback so you can wait for it to complete and get the final return value but remember to never have a task wait for other tasks Important Notes By default the synchronization step is implemented by having a recurring task poll the completion of the taskset every second applying the subtask when ready Example implementation def unlock _chord taskset callback interval l1 max_retries Ve if taskset ready return subtask callback delay taskset join unlock_chord retry countdown interval max_retries max_retries This is used by all result backends except Redis and Memcached which increment a counter after each task in the header then applying the callback when the counter exceeds the number of tasks in the set Note chords do not properly work with Redis before version 2 2 you will need to upgrade to at least 2 2 to use them The Redis and Memcached approach is a much better solution but not easily implemented in other backends sugges tions welcome Note If you are using chords with the Redis result backend and also overriding the Task after_return method you need to make sure to call the super method or else the chord callback will not be applied de
324. ll workers You can specify a single or a list of workers by using the destination argument celeryctl inspect d wl w2 reserved Django Admin Monitor New in version 2 1 When you add django celery to your Django project you will automatically get a monitor section as part of the Django admin interface This can also be used if you re not using Celery with a Django project Screenshot 68 Chapter 2 User Guide Celery Documeniation Release 2 5 5 Welcome askadmin Change password Log out Home gt Djcelery gt T Tasks a Search S By state 2010 All Action f ess 222 lt Go Oof 172 selected RETRY O uu State Name Args Kwargs ETA Worker O 5456f8ea SUCCESS statuses_twitter_update e97c687d13487t614a608176808t3d8e None h9 ST D f8c8 4778 96576157 e6ca 4841 b8d4 8b FAILURE 91b1 PENDING a468abc4f91f By name O b6fa561c SUCCESS portaloperacom refresh_portal_blog 0 None hl0 All 8f8a 4e39 9894 58403a21fb81 O ef256274 SUCCESS statuses_twitter_update e97c687413487t614a648176808t348e None h9 tasks refresh 7a73 4834 96576157 e6ca 48d1 b8d4 8b g 90fb By event received at 03f89e15aca6 Any date O 3359ba9e SUCCESS d Jrefresh_feed o teed_id 231L teed urt None h6 ee 7387 4d8f u NTtps wew CnDC Com 1d 19746125 Past 7 days ba7e This month 1fb6269ba396 This year O 51681ec8 SUCCESS statuses_twitter_update e970687d130871614a60817680813
325. lly Also as you may have noticed the contributors of new features fixes are now mentioned in the Changelog 178 Chapter 11 Change history Celery Documeniation Release 2 5 5 11 12 2 3 4 release date 2011 11 25 16 00 P M GMT by Ask Solem 11 12 1 Security Fixes e Security CELERYSA 0001 Daemons would set effective id s rather than real id s when the uid gid arguments to celeryd multi celeryd_detach celerybeat and celeryev were used This later means privileges weren t properly dropped and that it would be possible to regain supervisor privileges 11 12 2 Fixes e Backported fix for 455 from 2 4 to 2 3 e Statedb was not saved at shutdown e Fixes worker sometimes hanging when hard time limit exceeded 11 13 2 3 3 release date 2011 16 09 05 00 PM BST by Mher Movsisyan e Monkey patching sys stdout could result in the worker crashing if the replacing object did not define isa CEI tty Issue 477 ERYD option in etc default celeryd should not be used with generic init scripts 11 14 2 3 2 release date 2011 10 07 05 00 P M BST 11 14 1 News Improved Contributing guide If you d like to contribute to Celery you should read this guide http celery github com celery contributing html We are looking for contributors at all skill levels so don t hesitate Now depends on Kombu 1 3 1 Task request now contains the current worker host name Issue 460
326. local tasks sleeptask casper local tasks sleeptask casper local tasks sleeptask casper local tasks sleeptask casper local tasks sleeptask casper local tasks sleeptask casper local tasks sleeptask casper local tasks sleeptask casper local celeryev is also used to start snapshot cameras see Snapshots celeryev camera lt camera class gt frequency 1 0 and it includes a tool to dump events to stdout celeryev dump For a complete list of options use help celeryev help 10 02 21 SUCCESS 10 02 18 RECEIVED 10 02 18 RECEIVED 10 02 18 RECEIVED 10 02 18 RECEIVED 10 02 18 RECEIVED 10 02 18 RECEIVED 10 02 18 RECEIVED 10 02 18 RECEIVED 10 02 18 RECEIVED 10 02 18 RECEIVED 10 02 18 RECEIVED 10 02 18 RECEIVED 10 02 18 10 02 18 10 02 18 SUCCESS Selected runtime 3 01s eta 2010 06 04T10 02 21 513155 args 3 result 3 kwargs 2 9 Monitoring and Management Guide 71 Celery Documeniation Release 2 5 5 celerymon Web monitor celerymon is the ongoing work to create a web monitor It s far from complete yet and does currently only support a JSON API Help is desperately needed for this project so if you or someone you know would like to contribute templates design code or help this project in any way please get in touch Tip The Django admin monitor can be used even though you re not using Celery with a Django project See Using outside of Django 2 9 3 RabbitMQ To manage a Celery
327. log class celery log ColorFormatter msg use_color True COLORS blue lt bound method colored blue of gt black lt bound method colored black of gt yellow lt bound me Loglevel gt Color mapping colors DEBUG lt bound method colored blue of gt CRITICAL lt bound method colored magenta of gt WARN format record formatException ei class celery log Logging app colored logfile None get_default_logger loglevel None name celery Get default logger instance Parameters loglevel Initial log level get_task_logger loglevel None name None redirect_stdouts_to_logger logger loglevel None stdout True stderr True Redirect sys stdout and sys stderr to a logging instance Parameters e logger The logging Logger instance to redirect to e loglevel The loglevel redirected messages will be logged as setup loglevel None logfile None redirect_stdouts False redirect_level WARNING setup_logger loglevel None logfile None format None colorize None name celery root True app None kwargs Setup the multiprocessing logger 13 6 Internal Module Reference 371 Celery Documentation Release 2 5 5 If logfile is not specified then sys stderr is used Returns logger object setup_logging_subsystem loglevel None logfile None format None colorize None kwargs setup_task_logger loglevel None logfile None
328. lue is Unicode celery task http utf8dict tup With a dict s items tuple return a new dict with any utf 8 keys values encoded 12 13 celery schedules e celery schedules j 12 13 1 celery schedules Schedules define the intervals at which periodic tasks should run copyright 3 2009 2012 by Ask Solem license BSD see LICENSE for more details exception celery schedules ParseException Raised by crontab_parser when the input can t be parsed class celery schedules crontab minute hour day_of_week nowfun None A crontab can be used as the run_every value of a PeriodicTask to add cron like scheduling Like a cron job you can specify units of time of when you would like the task to execute Itis a reasonably complete implementation of cron s features so it should provide a fair degree of scheduling needs You can specify a minute an hour and or a day of the week in any of the following formats minute eA list of integers from 0 59 that represent the minutes of an hour of when execution should occur or eA string representing a crontab pattern This may get pretty advanced like minute 15 for every quarter or minute 1 13 30 45 50 59 2 hour eA list of integers from 0 23 that represent the hours of a day of when execution should occur or eA string representing a crontab pattern This may get pretty advanced like hour 3 for every three hours or hour
329. ly being executed inspect scheduled List scheduled ETA tasks 2 9 Monitoring and Management Guide 67 Celery Documentation Release 2 5 5 celeryctl inspect scheduled These are tasks reserved by the worker because they have the eta or countdown argument set e inspect reserved List reserved tasks celeryctl inspect reserved This will list all tasks that have been prefetched by the worker and is currently waiting to be executed does not include tasks with an eta e inspect revoked List history of revoked tasks celeryctl inspect revoked e inspect registered List registered tasks celeryctl inspect registered e inspect stats Show worker statistics celeryctl inspect stats inspect enable_events Enable events celeryctl inspect enable_events e inspect disable_events Disable events celeryctl inspect disable_events e migrate Migrate tasks from one broker to another EXPERIMENTAL celeryctl migrate redis localhost amgqp localhost This command will migrate all the tasks on one broker to another As this command is new and experimental you should be sure to have a backup of the data before proceeding Note All inspect commands supports a timeout argument This is the number of seconds to wait for responses You may have to increase this timeout if you re not getting a response due to latency Specifying destination nodes By default the inspect commands operates on a
330. ly saved taskset result Celerybeat now syncs every 3 minutes instead of only at shutdown Issue 382 Monitors now properly handles unknown events so user defined events are displayed Terminating a task on Windows now also terminates all of the tasks child processes Issue 384 celeryd I include option now always searches the current directory to import the specified modules Cassandra backend Now expires results by using TTLs Functional test suite in funtests is now actually working properly and passing tests 11 16 3 Fixes e celeryev was trying to create the pidfile twice e celery contrib batches Fixed problem where tasks failed silently Issue 393 e Fixed an issue where logging objects would give lt Unrepresentable even though the objects were e CELERY_TASK_ERROR_WHITE_LIST is now properly initialized in all loaders e celeryd_detach now passes through command line configuration e Remote control command add_consumer now does nothing if the queue is already being consumed from 11 17 2 2 8 release date 2011 11 25 16 00 P M GMT by Ask Solem 11 17 1 Security Fixes e Security CELERYSA 0001 Daemons would set effective id s rather than real id s when the uid gid arguments to celeryd multi celeryd_detach celerybeat and celeryev were used This means privileges weren t properly dropped and that it would be possible to regain supervisor privileges later 1
331. m number of retries before we give up re establishing a connection to the AMQP broker If this is set to 0 or None we will retry forever Default is 100 retries BROKER_TRANSPORT_OPTIONS New in version 2 2 A dict of additional options passed to the underlying transport See your transport user manual for supported options if any 3 2 15 Task execution settings CELERY_ALWAYS_EAGER If this is True all tasks will be executed locally by blocking until the task returns apply_async and Task delay will return an EagerResult instance which emulates the API and behavior of AsyncResult except the result is already evaluated That is tasks will be executed locally instead of being sent to the queue CELERY_EAGER_PROPAGATES_EXCEPTIONS If this is True eagerly executed tasks applied by task apply or when the CELERY_ALWAYS_EAGER setting is enabled will propagate exceptions It s the same as always running apply with throw True CELERY_IGNORE_RESULT Whether to store the task return values or not tombstones If you still want to store errors just not successful return values you can set CELERY_STORE_ERRORS_EVEN_IF_IGNORED 3 2 Configuration Directives 97 Celery Documeniation Release 2 5 5 CELERY_MESSAGE_COMPRESSION Default compression used for task messages Can be gzip bzip2 if available or any custom compression schemes registe
332. maining_estimate Optimization celeryd Store FAILURE result if the WorkerLostError exception occurs worker process disappeared celeryd Store FAILURE result if one of the 7imeLimitExceeded exceptions occurs Refactored the periodic task responsible for cleaning up results The backend cleanup task is now only added to the schedule if CELERY_TASK_RESULT_EXPIRES is set Ifthe schedule already contains a periodic task named celery backend_cleanup it won t change it so the behavior of the backend cleanup task can be easily changed The task is now run every day at 4 00 AM rather than every day since the first time it was run using crontab schedule instead of run_every Renamed celery task builtins DeleteExpiredTaskMetaTask gt celery task builtins backend_cleanup The task itself has been renamed from celery delete_expired_task_meta to cel ery backend_cleanup See issue 134 e Implemented AsyncResult forget for sqla cache redis tyrant backends Forget and remove task result See issue 184 11 30 2 1 0 203 Celery Documeniation Release 2 5 5 e TaskSetResult join Added propagate True argument When set to False exceptions occurring in subtasks will not be re raised e Added Task update_state task_id state meta as a shortcut to task backend store_result task_id meta state The backend interface is private and the terminology
333. mands also stops the heartbeat thread and event dispatcher Parameters close_connection Set to False to skip closing the broker connection stop_pidbox_node task_consumer None The consumer used to consume task messages update_strategies celery worker consumer INVALID_TASK_ERROR Received invalid task message s nThe message has been ignorec Error message for when an invalid task message is received celery worker consumer PREFETCH_COUNT_MAX 65535 Prefetch count can t exceed short 330 Chapter 13 Internals Celery Documeniation Release 2 5 5 class celery worker consumer QoS consumer initial_value logger Quality of Service for Channel For thread safe increment decrement of a channels prefetch count value Parameters e consumer A kombu messaging Consumer instance e initial_value Initial prefetch count value e logger Logger used to log debug messages decrement n Decrement the current prefetch count value by n decrement_eventually n Decrement the value but do not update the qos The MainThread will be responsible for calling update when necessary increment n Increment the current prefetch count value by n prev None set pcount Set channel prefetch_count setting update Update prefetch count with current value celery worker consumer UNKNOWN_TASK_ERROR Received unregistered task of type s nThe message has been ign Error message for wh
334. mber of members before we start evicting expired members e expires Time in seconds before a membership expires add value Add a new member as_dict chronologically clear Remove all members expires first Get the oldest member maxlen pop_value value Remove membership by finding value update other LRUCache class celery datastructures LRUCache imit None LRU Cache implementation using a doubly linked list to track access Parameters limit The maximum number of keys to keep in the cache When a new key is inserted and the limit has been exceeded the Least Recently Used key will be discarded from the cache incr key delta items iteritems itervalues keys values 13 6 37 celery routes e celery routes j 370 Chapter 13 Internals Celery Documeniation Release 2 5 5 celery routes Contains utilities for working with task routes CELERY_ROUTES copyright 3 2009 2012 by Ask Solem license BSD see LICENSE for more details class celery routes MapRoute map Creates a router out of a dict route_for_ task task args kwargs class celery routes Router routes None queues None create_missing False app None expand_destination route lookup_route task args None kwargs None route options task args kwargs celery routes prepare routes Expands the CELERY_ROUTES setting 13 6 38 celery
335. me Instantiation A task is not instantiated for every request but is registered in the task registry as a global instance This means that the __ init __ constructor will only be called once per process and that the task class is semantically closer to an Actor If you have a task class NaiveAuthenticateServer Task def init self users george password def run username password try return users username password except KeyError return 2 2 Tasks 29 Celery Documeniation Release 2 5 5 And you route every request to the same process then it will keep state between requests This can also be useful to keep cached resources class DatabaseTask Task _db None property def db self if self _db None self _db Database connect return self _db Abstract classes Abstract classes are not registered but are used as the base class for new task types class DebugTask Task abstract def after_return args xxkwargs print Task returned r request task base DebugTask def add x y return x y Handlers execute self request pool loglevel logfile x xkw Parameters e request A TaskRequest e pool The task pool e loglevel Current loglevel logfile Name of the currently used logfile e consumer The Consumer after_return self status retval task_id args kwargs einfo Handler called after the task retu
336. ments and keyword arguments e Requires carrot 0 3 8 e The daemon now tries to reconnect if the connection is lost 11 66 0 1 8 release date 2009 05 07 12 27 P M CET e Better test coverage e More documentation e celeryd doesn t emit Queue is empty message if settings CELERYD_EMPTY_MSG_EMIT_EVERY is 0 11 67 0 1 7 release date 2009 04 30 01 50 P M CET e Added some unit tests e Can now use the database for task metadata like if the task has been executed or not Set set tings CELERY_TASK_META e Can now run python setup py test to run the unit tests from within the tests project e Can set the AMQP exchange routing key queue using settings CELERY_AMQP_EXCHANGE set tings CELERY AMQP_ROUTING_KEY and settings CELERY_AMQP_CONSUMER_QUEUE 11 68 0 1 6 release date 2009 04 28 02 13 PM CET Introducing TaskSet A set of subtasks is executed and you can find out how many or if all them are done excellent for progress bars and such Now catches all exceptions when running Task __call pure functions yet only Task classes So the daemon doesn t die This doesn t happen for autodiscover now works with zipped eggs celeryd Now adds current working directory to sys path for convenience The run_every attribute of PeriodicTask classes can now be a datetime timedelta object celeryd You can now set the DJANGO_PROJECT_DIR variable for celeryd and it will add that to sys path for easy launching Ca
337. messages when the worker starts 9 3 11 I ve discarded messages but there are still messages left in the queue Answer Tasks are acknowledged removed from the queue as soon as they are actually executed After the worker has received a task it will take some time until it is actually executed especially if there are a lot of tasks already waiting for execution Messages that are not acknowledged are held on to by the worker until it closes the connection to the broker AMQP server When that connection is closed e g because the worker was stopped the tasks will be re sent by the broker to the next available worker or the same worker when it has been restarted so to properly purge the queue of waiting tasks you have to stop all the workers and then discard the tasks using discard_all 9 4 Results 9 4 1 How do get the result of a task if have the ID that points there Answer Use Task AsyncResult gt gt gt result MyTask AsyncResult task_id gt gt gt result get This will give you a BaseAsyncResult instance using the tasks current result backend If you need to specify a custom result backend you should use celery result BaseAsyncResult directly gt gt gt from celery result import BaseAsyncResult gt gt gt result BaseAsyncResult task_id backend gt gt gt result get 9 5 Security 9 5 1 Isn t using pickle a security concern Answer Yes indeed it is You are right to have a se
338. ml post get_object_or_404 Entry slug slug remote_addr request META get REMOTE_ADDR if request method post form CommentForm request POST request FILES if form is_valid comment form save tasks spam_filter delay comment_id comment id remote_addr remote_addr return HttpResponseRedirect post get_absolute_url else form CommentForm context RequestContext request form form return render_to_response template_name context_instance context To filter spam in comments we use Akismet the service used to filter spam in comments posted to the free weblog platform Wordpress Akismet is free for personal use but for commercial use you need to pay You have to sign up to their service to get an API key 36 Chapter 2 User Guide Celery Documeniation Release 2 5 5 To make API calls to Akismet we use the akismet py library written by Michael Foord blog tasks py from akismet import Akismet from celery task import task from django core exceptions import ImproperlyConfigured from django contrib sites models import Site from blog models import Comment task def spam_filter comment_id remote_addr ys logger spam_filter get_logger logger info Running spam filter for comment s comment_id comment Comment objects get pk comment_id current_domain Site objects get_current domain akismet Akismet settings AKISMET_KEY http s domain if not
339. mmands close_connection Closes the current broker connection and all open channels connection None The broker connection consume_messages Consume messages forever or until an exception is raised eta_schedule None Timer for tasks with an ETA countdown event_dispatcher None A celery events EventDispatcher for sending events heart None The thread that sends event heartbeats at regular intervals The heartbeats are used by monitors to detect that a worker went offline disappeared hostname None The current hostname Defaults to the system hostname info Returns information about this consumer instance as a dict This is also the consumer related info returned by celeryctl stats init_callback None Optional callback to be called when the connection is established Will only be called once even if the connection is lost and re established initial_prefetch_count 0 Initial QoS prefetch count for the task channel logger None The logger instance to use Defaults to the default Celery logger maybe_conn_error fun Applies function but ignores any connection or channel errors raised on_control body message Process remote control command message on_decode_error message exc Callback called if an error occurs while decoding a message received Simply logs the error and acknowledges the message so it doesn t enter a loop Parameters e message The message with errors e exc
340. mp_active Gives a list of tasks currently being executed by the worker By default arguments are passed through repr in case there are arguments that is not JSON encodable If you know the arguments are JSON safe you can pass the argument safe True Example reply 210 Chapter 11 Change history Celery Documeniation Release 2 5 5 gt gt gt broadcast arguments safe False reply True worker local args time_star e Added experimental support for persistent revokes Use the S statedb argument to celeryd to enable it celeryd statedb var run celeryd This will use the file var run celeryd db as the shelve module automatically adds the db suffix 11 34 2 0 0 release date 2010 07 02 02 30 PM CEST 11 34 1 Foreword Celery 2 0 contains backward incompatible changes the most important being that the Django dependency has been removed so Celery no longer supports Django out of the box but instead as an add on package called django celery We re very sorry for breaking backwards compatibility but there s also many new and exciting features to make up for the time you lose upgrading so be sure to read the News section Quite a lot of potential users have been upset about the Django dependency so maybe this is a chance to get wider adoption by the Python community as well Big thanks to all contributors testers and users 11 34 2 Upgrading for Django users Django in
341. mq com faq html node runs out of memory Note This is no longer the case RabbitMQ versions 2 0 and above includes a new persister that is tolerant to out of memory errors RabbitMQ 2 1 or higher is recommended for Celery If you re still running an older version of RabbitMQ and experience crashes then please upgrade Misconfiguration of Celery can eventually lead to a crash on older version of RabbitMQ Even if it doesn t crash this can still consume a lot of resources so it is very important that you are aware of the common pitfalls e Events Running celeryd with the E event s option will send messages for events happening inside of the worker Events should only be enabled if you have an active monitor consuming them or if you purge the event queue period ically e AMQP backend results When running with the AMQP result backend every task result will be sent as a message If you don t collect these results they will build up and RabbitMQ will eventually run out of memory Results expire after 1 day by default It may be a good idea to lower this value by configuring the CELERY_TASK_RESULT_EXPIRES setting If you don t use the results for a task make sure you set the ignore_result option 9 6 Brokers 155 Celery Documeniation Release 2 5 5 9 6 2 Can I use Celery with Active MQ STOMP Answer No It used to be supported by Carrot but is not currently supported in Kombu 9
342. n New in version 2 2 12 9 celery result 271 Celery Documentation Release 2 5 5 Note that this does not support collecting the results for different task types using different backends This is currently only supported by the AMQP Redis and cache result backends ready Did all of the tasks complete either by success of failure Returns True if all of the tasks been executed remove result Removes result from the set it must be a member Raises KeyError if the result is not a member results None List of results in in the set revoke connection None connect_timeout None Revoke all tasks in the set subtasks Deprecated alias to results successful Was all of the tasks successful Returns True if all of the tasks finished successfully i e did not raise an exception supports _native_join total Deprecated Use len r update results Update set with the union of itself and an iterable with results waiting Are any of the tasks incomplete Returns True if any of the tasks is still waiting for execution class celery result TaskSetResult taskset_id results None kwargs An instance of this class is returned by JaskSet s apply_async method It enables inspection of the tasks state and return values as a single entity Parameters e taskset_id The id of the taskset e results List of result instances delete backend None Remove this result if it was pr
343. n Release 2 5 5 11 45 0 8 1 release date 2009 11 16 05 21 P M CEST 11 45 1 Very important note This release with carrot 0 8 0 enables AMQP QoS quality of service which means the workers will only receive as many messages as it can handle at a time As with any release you should test this version upgrade on your development servers before rolling it out to production 11 45 2 Important changes e If you re using Python lt 2 6 and you use the multiprocessing backport then multiprocessing version 2 6 2 1 is required AMQOP_SERVER localhost AMQP_PORT 5678 AMQP_USER myuser AMOP_PASSWORD mypassword AMQP_VHOST celery You need to change that to BROKER_HOST localhost BROKER_PORT 5678 BROKER_USER myuser BROKER_PASSWORD mypassword BROKER_VHOST celery CARROT_BACKEND mycustom backend module you need to change it to CARROT_BACKEND mycustom backend module Backend where Backend is the class name This is probably Backend as that was the previously implied name e New version requirement for carrot 0 8 0 11 45 3 Changes e Incorporated the multiprocessing backport patch that fixes the processName error e Ignore the result of PeriodicTask s by default e Added a Redis result store backend e Allow etc default celeryd to define additional options for the celeryd init script e MongoDB periodic tasks issue when usin
344. n Release 2 5 5 class celery bin celeryct1 shell app None no_color False invoke_bpython_shell1 invoke_default_shell1 invoke_fallback_shell1 invoke_ipython_shell1 option_list lt Option at 0x5c213f8 app gt lt Option at Ox5acf950 b broker gt lt Option at Ox5acf998 loader gt lt C run force_ipython False force_bpython False force_python False without_tasks False event let False gevent False kwargs class celery bin celeryctl status app None no_color False option_list lt Option at 0x5c213f8 app gt lt Option at 0x5acf950 b broker gt lt Option at 0x5acf998 loader gt lt C run args kwargs 12 37 celery bin camqadm camqadm class celery bin camqadm AMOQPAdmin args kwargs The celery camqadm utility connect conn None run say m class celery bin camqadm AMQPAdminCommand app None get_app None run args options class celery bin camqadm AMQShe11 args kwargs AMQP API Shell Parameters e connect Function used to connect to the server must return connection object e silent If True the commands won t have annoying output not relevant when running in non shell mode amqp Mapping of AMQP API commands and their Spec amqp queue declare lt celery bin camqadm Spec object at 0x333ee90 gt queue purge lt celery bin camqadm Spec obj builtins exit do_exit EOF d
345. n connect your handler to be called only when tasks with name tasks add has been sent by providing the sender argument to connect task_sent connect task_sent_handler sender tasks add def task_sent_handler sender task_id task args kwargs kwds print Got signal task_sent for task id s task_id 2 13 Signals 81 Celery Documentation Release 2 5 5 2 13 2 Signals Task Signals task_sent Dispatched when a task has been sent to the broker Note that this is executed in the client process the one sending the task not in the worker Sender is the name of the task being sent Provides arguments e task_id Id of the task to be executed e task The task being executed e args the tasks positional arguments e kwargs The tasks keyword arguments e eta The time to execute the task e taskset Id of the taskset this task is part of if any task_prerun Dispatched before a task is executed Sender is the task class being executed Provides arguments e task_id Id of the task to be executed e task The task being executed e args the tasks positional arguments e kwargs The tasks keyword arguments task_postrun Dispatched after a task has been executed Sender is the task class executed Provides arguments e task_id Id of the task to be executed e task The task being executed e args The tasks positional arguments e kwargs The tasks keyword arguments e retv
346. n now check if a task has been executed or not via HTTP You can do this by including the celery urls py into your project 11 65 0 1 10 243 Celery Documentation Release 2 5 5 gt gt gt url r celery include celery urls then visiting the following url http mysite celery Stask_id done this will return a JSON dictionary like e g gt gt gt task id Stask_id executed true e delay_task now returns string id not uuid UUID instance e Now has PeriodicTasks to have cron like functionality e Project changed name from crunchy to celery The details of the name change request is in docs name_change_request txt 11 69 0 1 0 release date 2009 04 24 11 28 A M CET e Initial release 244 Chapter 11 Change history CHAPTER 12 API Reference Release 2 5 Date February 04 2014 12 1 celery app Celery Application copyright 3 2009 2012 by Ask Solem license BSD see LICENSE for more details 12 1 1 Application e Application e Functions class celery app App main None loader None backend None amqp None events None log None control None set_as_current True accept_magic_kwargs False kwargs Celery Application Parameters celery loaders app AppLoader main Name of the main module if running as ___main__ loader The loader class or the name of the loader class to use Default is backend The result store backend cla
347. n use the workers logger to add diagnostic output to the worker log 2 2 Tasks 21 Celery Documeniation Release 2 5 5 task def add x y logger add get_logger logger info Adding s Ss x y return x y There are several logging levels available and the workers oglevel setting decides whether or not they will be written to the log file Of course you can also simply use print as anything written to standard out err will be written to the log file as well 2 2 4 Retrying a task if something fails Simply use ret ry to re send the task It will do the right thing and respect the max_ret ries attribute task def send_twitter_status oauth tweet try twitter Twitter oauth twitter update_status tweet except Twitter FailWhaleError Twitter LoginError exc send_twitter_status retry exc exc Here we used the exc argument to pass the current exception to ret ry At each step of the retry this exception is available as the tombstone result of the task When max_ret ries has been exceeded this is the exception raised However if an exc argument is not provided the Ret ryTaskError exception is raised instead Note The retry call will raise an exception so any code after the retry will not be reached This is the celery exceptions RetryTaskError exception it is not handled as an error but rather as a semi predicate to signify to the worker that the task is to be retried
348. name for the exchange CELERY_RESULT_EXCHANGE celeryresults2 But you have to make sure that all clients and workers use this new setting so they are updated to use the same exchange name 10 1 3 Solution for hanging workers but must be manually enabled The CELERYD_FORCE_EXECV setting has been added to solve a problem with deadlocks that originate when threads and fork is mixed together CELERYD_FORCE_EXECV This setting is recommended for all users using the processes pool but especially users also using time limits or a max tasks per child setting e See Python Issue 6721 to read more about this issue and why resorting to execv is the only safe solution Enabling this option will result in a slight performance penalty when new child worker processes are started and it will also increase memory usage but many platforms are optimized so the impact may be minimal Considering that it ensures reliability when replacing lost worker processes it should be worth it e It s already the default behavior on Windows e It will be the default behavior for all platforms in a future version 10 2 Optimizations e The code path used when the worker executes a task has been heavily optimized meaning the worker is able to process a great deal more tasks second compared to previous versions As an example the solo pool can now process up to 15000 tasks second
349. nc Now supports the accept_callback argument apply_async Now raises ValueError if task args is not a list or kwargs is not a tuple Issue 95 Task max_retries can now be None which means it will retry forever Celerybeat Now reuses the same connection when publishing large sets of tasks Modified the task locking example in the documentation to use cache add for atomic locking Added experimental support for a started status on tasks If Task track_started is enabled the task will report its status as started when the task is executed by a worker The default value is False as the normal behaviour is to not report that level of granularity Tasks are either pending finished or waiting to be retried Having a started status can be useful for when there are long running tasks and there is a need to report which task is currently running The global default can be overridden by the CELERY_TRACK_STARTED setting e User Guide New section Tips and Best Practices Contributions welcome 222 Chapter 11 Change history Celery Documeniation Release 2 5 5 11 38 3 Remote control commands e Remote control commands can now send replies back to the caller Existing commands has been improved to send replies and the client interface in celery task control has new keyword arguments reply timeout and limit Where reply means it will wait for replies timeout is the time in seconds to stop waiting f
350. nce unlike join which fetches the results one by one So far only supported by the AMQP result backend Support for memcached and Redis may be added later e Improved implementations of TaskSetResultjoin and AsyncResult wait An interval keyword argument have been added to both so the polling interval can be specified default interval is 0 5 seconds 194 Chapter 11 Change history Celery Documeniation Release 2 5 5 A propagate keyword argument have been added to result wait errors will be returned instead of raised if this is set to False Warning You should decrease the polling interval when using the database result backend as frequent polling can result in high database load The PID of the child worker process accepting a task is now sent as a field with the task started event The following fields have been added to all events in the worker class sw_ident Name of worker software e g celeryd sw_ver Software version e g 2 2 0 sw_sys Operating System e g Linux Windows Darwin For better accuracy the start time reported by the multiprocessing worker process is used when calculating task duration Previously the time reported by the accept callback was used celerybeat New built in daemonization support using the detach option celeryev New built in daemonization support using the detach option TaskSet apply_async Now supports custom publishers by using the publis
351. nd line celeryd b redis localhost celeryctl b amaqp guest guest localhost e The environment variable CELERY_BROKER_URL can also be used to easily override the default broker used e The deprecated celery loaders setup_loader function has been removed e The CELERY_TASK_ERROR_WHITELIST setting has been replaced by a more flexible approach Issue 447 The error mail sending logic is now available as Task ErrorMail with the implementation for reference in celery utils mail The error mail class can be sub classed to gain complete control of when error messages are sent thus removing the need for a separate white list setting The CELERY_TASK_ERROR_WHITELIST setting has been deprecated and will be removed com pletely in version 3 0 e Additional Deprecations The following functions has been deprecated and is scheduled for removal in version 3 0 Old function Alternative celery loaders current_loader celery current_app loader celery loaders load_settings celery current_app conf celery execute apply Task apply celery execute apply_async Task apply_async celery execute delay_task celery execute send_task The following settings has been deprecated and is scheduled for removal in version 3 0 176 Chapter 11 Change history Celery Documeniation Release 2 5 5 Old setting Alternative CELERYD_LOG_LEVEL celeryd l
352. nfiguration other than the URL location of the broker instance you want to use gt gt gt BROKER_URL amqp guest guest localhost 5672 For a description of broker URLs and a full list of the various broker configuration options available to Celery see Broker Settings Installing the RabbitMQ Server See Installing RabbitMQ over at RabbitMQ s website For Mac OS X see Installing RabbitMQ on OS X Note If you re getting nodedown errors after installing and using rabbitmqctl then this blog post can help you identify the source of the problem http somic org 2009 02 19 on rabbitmqctl and badrpcnodedown Setting up RabbitMQ To use celery we need to create a RabbitMQ user a virtual host and allow that user access to that virtual host rabbitmqctl add_user myuser mypassword rabbitmqctl add_vhost myvhost rabbitmqctl set_permissions p myvhost myuser le lx See the RabbitMQ Admin Guide for more information about access control Installing RabbitMQ on OS X The easiest way to install RabbitMQ on Snow Leopard is using Homebrew the new and shiny package management system for OS X In this example we ll install Homebrew into 101 but you can choose whichever destination even in your home directory if you want as one of the strengths of Homebrew is that it s relocatable Homebrew is actually a git repository so to install Homebrew you first need to install git Download and install from the disk
353. ng and that s just about it It will use the default one second timeout for replies unless you specify a custom timeout gt gt gt from celery task control import ping gt gt gt ping timeout 0 workerl example a yrker2 example l f l rker3 example ping also supports the destination argument so you can specify which workers to ping gt gt gt ping worker2 example com worker3 example com 1 Or 2 example com 3 example com Enable disable events You can enable disable events by using the enable_events disable_events commands This is useful to temporarily monitor a worker using celeryev celerymon gt gt gt broadcast enable_events gt gt gt broadcast disable_events Adding Reloading modules New in version 2 5 The remote control command pool_restart sends restart requests to the workers child processes It is particularly useful for forcing the worker to import new modules or for reloading already imported modules This command does not interrupt executing tasks Example Running the following command will result in the foo and bar modules being imported by the worker processes gt gt gt from celery task control import broadcast gt gt gt broadcast pool_restart arguments modules foo bar Use the reload argument to reload modules it has already imported gt gt gt broadcast pool_restart arguments modules
354. ng level Can be any of DEBUG INFO WARNING ERROR or CRITICAL Can also be set via the loglevel argument to celerybeat See the logging module for more information CELERYMON_LOG_FILE Deprecated since version 2 4 This option is deprecated and is scheduled for removal in version 3 0 Please use the logfile argument instead The default file name to log messages to Can be overridden using the logfile argument to celerymon The default is None stderr CELERYMON_LOG_LEVEL Deprecated since version 2 4 This option is deprecated and is scheduled for removal in version 3 0 Please use the logleve1 argument instead Logging level Can be any of DEBUG INFO WARNING ERROR or CRITICAL See the logging module for more information 3 2 Configuration Directives 107 Celery Documeniation Release 2 5 5 108 Chapter 3 Configuration and defaults CHAPTER 4 Django Release 2 5 Date February 04 2014 4 1 First steps with Django 4 1 1 Configuring your Django project to use Celery You need four simple steps to use celery with your Django project 1 Install the django celery library S pip install django celery 2 Add the following lines to sett ings py import djcelery djcelery setup_loader 3 Add djcelery to INSTALLED_APPS 4 Create the celery database tables If you are using south for schema migrations you ll want to S python manage py migrate djcelery For thos
355. ng over it Issue 501 The Cache Cassandra MongoDB Redis and Tyrant backends now respects the CELERY_RESULT_SERIALIZER setting Issue 435 This means that only the database django sqlalchemy backends currently does not support using custom serializers Contributed by Steeve Morin Logging calls no longer manually formats messages but delegates that to the logging system so tools like Sentry can easier work with the messages Issue 445 Contributed by Chris Adams celeryd_multi now supports a stop_verify command to wait for processes to shutdown Cache backend did not work if the cache key was unicode Issue 504 11 11 2 4 0 177 Celery Documentation Release 2 5 5 Fix contributed by Neil Chintomby New setting CELERY_RESULT_DB_SHORT_LIVED_SESSIONS added which if enabled will disable the caching of SQLAIchemy sessions Issue 449 Contributed by Leo Dirac All result backends now implements __reduce__ so that they can be pickled Issue 441 Fix contributed by Remy Noel celeryd multi did not work on Windows Issue 472 New style CELERY_REDIS__ settings now takes precedence over the old REDIS__ configuration keys Issue 508 Fix contributed by Joshua Ginsberg Generic celerybeat init script no longer sets bash e Issue 510 Fix contributed by Roger Hu Documented that Chords do not work well with redis server versions bef
356. nger auto delete Solution for hanging workers but must be manually enabled e Optimizations e Deprecations Removals Deprecations e News Timezone support New security serializer using cryptographic signing Experimental support for automatic module reloading New CELERY_ANNOTATIONS setting current provides the currently executing task In Other News e Fixes 10 1 Important Notes 10 1 1 Broker connection pool now enabled by default The default limit is 10 connections if you have many threads green threads using connections at the same time you may want to tweak this limit to avoid contention 161 Celery Documeniation Release 2 5 5 See the BROKER_POOL_LIMIT setting for more information Also note that publishing tasks will be retried by default to change this default or the default retry policy see CELERY_TASK_PUBLISH_RETRY and CELERY_TASK_PUBLISH_RETRY_POLICY 10 1 2 AMQP Result Backend Exchange is no longer auto delete The exchange used for results used to have the auto_delete flag set that could result in a race condition leading to an annoying warning For RabbitMQ users Old exchanges created with the auto_delete flag enabled has to be removed The camqadm command can be used to delete the previous exchange camqadm exchange delete celeryresults As an alternative to deleting the old exchange you can configure a new
357. ngs Available options CELERYD_NODES Node names to start CELERYD_OPTS Additional arguments to celeryd see celeryd help for a list CELERYD_CHDIR Path to change directory to at start Default is to stay in the current directory CELERYD_PID_FILE Full path to the PID file Default is var run celeryd n pid CELERYD_LOG_FILE Full path to the celeryd log file Default is var log celeryd n log 116 Chapter 5 Cookbook Celery Documeniation Release 2 5 5 e CELERYD_LOG_LEVEL Log level to use for celeryd Default is INFO e CELERYD_MULTI Path to the celeryd multi program Default is celeryd multi You can point this to a virtualenv or even use manage py for django e CELERYCTL Path to the celeryctl program Default is celeryctl You can point this to a virtualenv or even use manage py for django e CELERYD_USER User to run celeryd as Default is current user e CELERYD_GROUP Group to run celeryd as Default is current user Init script celerybeat Usage etc init d celerybeat start stop restart Configuration file etc default celerybeat or etc default celeryd Example configuration This is an example configuration for a Python project etc default celerybeat WNeELE C ar CELERYBEAT_CHDIR opt Myproject CELERYBEAT_OPTS schedule var run celerybeat schedule eLer nrig I QULE j ERY_CONFIG_MODULE celeryconfig aQ io Example Django configurat
358. now need cel ery loaders default Loader using the previous syntax will result in a Deprecation Warning e Detecting the loader is now lazy and so is not done when importing celery loaders To make this happen celery loaders settings has been renamed to load_settings and is now a function returning the settings object celery loaders current_loader is now also a function returning the current loader So 11 41 1 0 0 229 Celery Documentation Release 2 5 5 11 11 loader current_loader needs to be changed to loader current_loader 41 2 Deprecations e The following configuration variables has been renamed and will be deprecated in v2 0 CELERYD_DAEMON_LOG_FORMAT gt CELERYD_LOG_FORMAT CELERYD_DAEMON_LOG_LEVEL gt CELERYD_LOG_LEVEL CELERY_AMQP_CONNECTION_TIMEOUT gt CELERY_BROKER_CONNECTION_TIMEOUT CELERY_AMQP_CONNECTION_RETRY gt CELERY_BROKER_CONNECTION_RETRY CELERY_AMQP_CONNECTION_MAX_RETRIES gt CELERY_BROKER_CONNECTION_MAX_RETRIES SEND_CELERY_TASK ERROR EMAILS gt CELERY_SEND_TASK_ERROR_EMAILS e The public API names in celery conf has also changed to a consistent naming scheme e We now support consuming from an arbitrary number of queues To do this we had to rename the configuration syntax If you use any of the custom AMQP routing options queue exchange routing_key etc you should read the new FAQ entry http bit ly aiWoH The previous syntax is deprecate
359. nowledgment to signify that a message has been received and processed successfully If the message has not been acknowledged and consumer channel is closed the message will be delivered to another consumer Note the delivery tag listed in the structure above Within a connection channel every received message has a unique delivery tag This tag is used to acknowledge the message Also note that delivery tags are not unique across connec tions so in another client the delivery tag 7 might point to a different message than in this channel You can acknowledge the message we received using basic ack 6 gt basic ack 1 ok To clean up after our test session we should delete the entities we created 7 gt queue delete testqueu ok 0 messages deleted 8 gt exchange delete testexchang ok 2 8 3 Routing Tasks Defining queues In Celery available queues are defined by the CELERY_QUEUES setting 64 Chapter 2 User Guide Celery Documeniation Release 2 5 5 Here s an example queue configuration with three queues One for video one for images and one default queue for everything else CELERY_QUEUES default exchange default binding_key default videos exchange media exchange_type topic bDinding_key media video he images exchange media exchange_type topic binding_key media image
360. nstead of silenced celeryd will then show the full traceback of these errors in the log e AMQP Backend No longer deletes the result queue after successful poll as this should be handled by the CELERY_AMOP_TASK_RESULT_EXPIRES setting instead e AMQP Backend Now ensures queues are declared before polling results Windows celeryd Show error if running with B option Running celerybeat embedded is known not to work on Windows so users are encouraged to run celerybeat as a separate service instead Windows Utilities no longer output ANSI color codes on Windows camqadm Now properly handles Ctrl C by simply exiting instead of showing confusing traceback Windows All tests are now passing on Windows Remove bin directory and scripts section from setup py This means we now rely completely on setuptools entrypoints 11 25 4 Experimental e Jython celeryd now runs on Jython using the threaded pool All tests pass but there may still be bugs lurking around the corners e PyPy celeryd now runs on PyPy It runs without any pool so to get parallel execution you must start multiple instances e g using celeryd multi Sadly an initial benchmark seems to show a 30 performance decrease on pypy 1 4 1 JIT We would like to find out why this is so stay tuned e PublisherPool Experimental pool of task publishers and connections to be used with the retry argument to apply_async The example code bel
361. nsumer can be can celled either explicitly or because its channel is closed If there was no consumer ever on the queue it won t be deleted queue_arguments Additional arguments used when declaring the queue binding_arguments Additional arguments used when binding the queue alias Unused in Kombu but applications can take advantage of this For example to give alternate names to queues with automatically generated queue names attrs name None exchange None routing_key None queue_arguments None binding_argume auto_delete False can_cache_ declaration cancel consumer_tag Cancel a consumer by consumer tag consume consumer_tag callback None no_ack None nowait False Start a queue consumer Consumers last as long as the channel they were created on or until the client cancels them Parameters e consumer_tag Unique identifier for the consumer The consumer tag is local to a connection so two clients can use the same consumer tags If this field is empty the server will generate a unique tag e no_ack If set messages received does not have to be acknowledged e nowait Do not wait for a reply e callback callback called for each delivered message declare nowait False Declares the queue the exchange and binds the queue to the exchange delete if_unused False if_empty False nowait False Delete the queue Parameters e if unused If set th
362. nsumers and brokers The client sending messages is typically called a publisher or a producer while the entity receiving messages is called a consumer The broker is the message server routing messages from producers to consumers You are likely to see these terms used a lot in AMQP related material 2 8 Routing Tasks 61 Celery Documentation Release 2 5 5 Exchanges queues and routing keys 1 Messages are sent to exchanges 2 An exchange routes messages to one or more queues Several exchange types exists providing different ways to do routing or implementing different messaging scenarios 3 The message waits in the queue until someone consumes it 4 The message is deleted from the queue when it has been acknowledged The steps required to send and receive messages are 1 Create an exchange 2 Create a queue 3 Bind the queue to the exchange Celery automatically creates the entities necessary for the queues in CELERY_QUEUES to work except if the queue s auto_declare setting is set to False Here s an example queue configuration with three queues One for video one for images and one default queue for everything else CELERY_QUEUES default exchange default binding_key default videos exchange media binding_key media video Fr images exchange media binding_key media image
363. nually to read the resulting error output For example my sh x output does this start stop daemon start chdir opt Opal release opal quiet oknodo background make pidfil pidfile var run celeryd pid exec opt Opal release opal manage py celeryd time limit 300 f var log celeryd log 1 INFO Run the celeryd command after exec without the to show the actual resulting output opt Opal release opal manage py celeryd time limit 300 f var log celeryd log 1 INFO 5 2 2 supervisord e contrib supervisord 5 2 3 launchd OS X e contrib mac 5 2 4 Windows See this excellent external tutorial http www calazan com windows tip run applications in the background using task scheduler This page contains common recipes and techniques 118 Chapter 5 Cookbook CHAPTER 6 Contributing 119 Celery Documentation Release 2 5 5 e Community Code of Conduct Be considerate Be respectful Be collaborative When you disagree consult others When you are unsure ask for help Step down considerately e Reporting a Bug Issue Trackers e Versions e Branches master branch Maintenance branches Archived branches Feature branches e Tags e Working on Features amp Patches Forking and setting up the repository Running the unit test suite Creating pull requests x Calculating test coverage x Running the test
364. o use Celery you need at least two main components a message broker and a worker 17 Celery Documentation Release 2 5 5 The message broker enables clients and workers to communicate through messaging There are several broker imple mentations available the most popular being RabbitMQ The worker processes messages and consists of one or more physical or virtual nodes 2 1 1 Tasks The action to take whenever a message of a certain type is received is called a task e Go to Tasks e Go to Executing Tasks Go to Sets of tasks Subtasks and Callbacks e Go to Periodic Tasks e Go to HTTP Callback Tasks Webhooks 2 1 2 Workers Go to Workers Guide 2 1 3 Monitoring Go to Monitoring and Management Guide 2 1 4 Routing JOxIOM 104019 Figure 2 2 Figure 2 Worker bindings Go to Routing Tasks Celery takes advantage of AMQPs flexible routing model Tasks can be routed to specific servers or a cluster of servers by binding workers to different queues A single worker node can be bound to one or more queues Multiple messaging scenarios are supported round robin point to point broadcast one to many and more 18 Chapter 2 User Guide Celery Documentation Release 2 5 5 Celery aims to hide the complexity of AMQP through features like Automatic routing while still preserving the ability to go low level if that should be necessary 2 1 5 Ecosystem Kombu cyme celerymon 2 2 Tasks
365. o_exit help do_help chan None completenames text ignored Return all commands starting with text for tab completion conn None 304 Chapter 12 API Reference Celery Documeniation Release 2 5 5 counter 1 default line dispatch cmd argline Dispatch and execute the command Lookup order is builtins gt amqp display _command_help cmd short False do_exit args The exit command do_help args get_amqp_api_command cmd arglist With a command name and a list of arguments convert the arguments to Python values and find the corresponding method on the AMQP channel object Returns tuple of method processed_args Example gt gt gt get_amgp_api_command queue delete pobox yes no lt bound method Channel que get_names identchars inc_counter lt method wrapper next of itertools count object at 0x74c3950 gt needs_reconnect False onecmd line Parse line and execute command parseline line Parse input line Returns tuple of three items command_name arglist original_line E g gt gt gt parseline queue delete A B C a pr an a 5 queue delete A B C queue delete A prompt prompt_fmt d gt respond retval What to do with the return value of a command say m Say something to the user Disabled if silent class celery bin camqadm Spec args kwargs
366. oduction The default configuration makes a lot of compromises It s not optimal for any single case but works well enough for most situations There are optimizations that can be applied based on specific use cases Optimizations can apply to different properties of the running environment be it the time tasks take to execute the amount of memory used or responsiveness at times of high load 2 11 2 Ensuring Operations In the book Programming Pearls Jon Bentley presents the concept of back of the envelope calculations by asking the question How much water flows out of the Mississippi River in a day The point of this exercise is to show that there is a limit to how much data a system can process in a timely manner Back of the envelope calculations can be used as a means to plan for this ahead of time In Celery If a task takes 10 minutes to complete and there are 10 new tasks coming in every minute the queue will never be empty This is why it s very important that you monitor queue lengths A way to do this is by using Munin You should set up alerts that will notify you as soon as any queue has reached an unacceptable size This way you can take appropriate action like adding new worker nodes or revoking unnecessary tasks 2 11 3 General Settings Broker Connection Pools The broker connection pool is enabled by default since version 2 5 You can tweak the BROKER_POOL_LIMIT setting to minimize contention and the v
367. oglevel CELERYD_LOG_FILE celeryd logfile CELERYBEAT_LOG_LEVEL celerybeat loglevel CELERYBEAT_LOG_FILE celerybeat logfile CELERYMON_LOG_LEVEL celerymon loglevel CELERYMON_LOG_FILE celerymon logfile 11 11 2 News e No longer depends on pyparsing e Now depends on Kombu 1 4 3 e CELERY_IMPORTS can now be a scalar value Issue 485 It is too easy to forget to add the comma after the sole element of a tuple and this is something that often affects newcomers The docs should probably use a list in examples as using a tuple for this doesn t even make sense Nonetheless there are many tutorials out there using a tuple and this change should be a help to new users Suggested by jsaxon cars Fixed a memory leak when using the thread pool Issue 486 Contributed by Kornelijus Survila The statedb was not saved at exit This has now been fixed and it should again remember previously revoked tasks when a statedb is enabled Adds EMAIL_USE_TLS to enable secure SMTP connections Issue 418 Contributed by Stefan Kjartansson Now handles missing fields in task messages as documented in the message format documentation Missing required field throws InvalidTaskError Missing args kwargs is assumed empty Contributed by Chris Chamberlin Fixed race condition in celery events state celerymon celeryev where task info would be removed while iterat i
368. on version Dump version info and exit e celeryd mul1ti Tool for shell scripts to start multiple workers 218 Chapter 11 Change history Celery Documeniation Release 2 5 5 Some examples Advanced example with 10 workers Thr of the workers processes the images and video queue x Two of the workers processes the data queue with loglevel DEBUG x the rest processes the default queue celeryd multi start 10 1 INFO Q 1 3 images video Q 4 5 data Q default L 4 5 DEBUG get commands to start 10 workers with 3 processes each celeryd multi start 3 c 3 celeryd n celerydl myhost c 3 c Cc leryd n celeryd2 myhost c 3 leryd n celeryd3 myhost c 3 start 3 named workers celeryd multi start image video data c 3 c c leryd n image myhost c 3 leryd n video myhost c 3 celeryd n data myhost c 3 specify custom hostname celeryd multi start 2 n worker example com c 3 leryd n celerydl worker example com c 3 leryd n celeryd2 worker example com c 3 QQ WH Additionl options are added to each celeryd but you can also modify the options for ranges of or single workers 3 workers Two with 3 processes and one with 10 processes celeryd multi start 3 c 3 c 1 10 leryd n celerydl myhost c 10 leryd n celeryd2 myhost c 3 leryd n celeryd3 myhost c 3 QqQaQqaq nm
369. on a 4 core MacBook Pro when using the pylibrabbitmq transport where it previously could only do 5000 tasks second e The task error tracebacks are now much shorter e Fixed a noticeable delay in task processing when rate limits are enabled 162 Chapter 10 What s new in Celery 2 5 Celery Documeniation Release 2 5 5 10 3 Deprecations 10 3 1 Removals The old TaskSet signature of task_name list_of_tasks can no longer be used originally sched uled for removal in 2 4 The deprecated t ask_name and task attributes has also been removed e The functions celery execute delay_task celery execute apply and celery execute apply_async has been removed originally scheduled for removal in 2 3 The built in ping task has been removed originally scheduled for removal in 2 3 Please use the ping broadcast command instead It is no longer possible to import subtask and TaskSet from celery task base please import them from celery task instead originally scheduled for removal in 2 4 10 3 2 Deprecations e The celery decorators module has changed status from pending deprecation to deprecated and is sched uled for removal in version 3 0 The celery task module must be used instead 10 4 News 10 4 1 Timezone support Celery can now be configured to treat all incoming and outgoing dates as UTC and the local timezone can be config ured This is not yet enabled by default since enabling time zone support me
370. only be one instance of this service Q queues List of queues to enable for this worker separated by comma By default all configured queues are enabled Example Q video image I include Comma separated list of additional modules to import Example I foo tasks bar tasks s schedule Path to the schedule database if running with the B option Defaults to celerybeat schedule The extension db will be appended to the filename scheduler Scheduler class to use Default is celery beat PersistentScheduler E events Send events that can be captured by monitors like celerymon purge discard Discard all waiting tasks before the daemon is started WARNING This is unrecoverable and the tasks will be deleted from the messaging server time limit Enables a hard time limit in seconds for tasks soft time limit Enables a soft time limit in seconds for tasks 300 Chapter 12 API Reference Celery Documeniation Release 2 5 5 maxtasksperchild Maximum number of tasks a pool worker can execute before it s terminated and replaced by a new worker class celery bin celeryd WorkerCommand app None get_app None enable_config_from_cmdline True get_options namespace celeryd run args kwargs supports_args False celery bin celeryd main 12 34 celery bin celerybeat celerybeat s 1 schedule Path to the schedule database Defaults to celerybeat s
371. or E Mails CELERY_SEND_TASK_ERROR_EMAILS The default value for the Task send_error_emails attribute which if set to True means errors occurring during task execution will be sent to ADMINS by email Disabled by default ADMINS List of name email_address tuples for the administrators that should receive error emails SERVER_EMAIL The email address this worker sends emails from Default is celery localhost EMAIL_HOST The mail server to use Default is localhost EMAIL_HOST_USER User name if required to log on to the mail server with EMAIL_HOST_PASSWORD Password if required to log on to the mail server with EMAIL_PORT The port the mail server is listening on Default is 25 3 2 Configuration Directives 101 Celery Documeniation Release 2 5 5 EMAIL_USE_SSL Use SSL when connecting to the SMTP server Disabled by default EMAIL_USE_TLS Use TLS when connecting to the SMTP server Disabled by default EMAIL_TIMEOUT Timeout in seconds for when we give up trying to connect to the SMTP server when sending emails The default is 2 seconds Example E Mail configuration This configuration enables the sending of error emails to george vandelay com and kramer vandelay com ADMINS George Costanza george vandelay com Cosmo Kramer kosmo vandelay com jdress used as sender From field EMAIL no reply vandelay com
372. or Fridays Execute every even hour and every hour divisible by three This means at every hour except lam 5am 7am llam lpm 5pm 7pm 11pm Execute hour divisible by 5 This means that it is trig gered at 3pm not 5pm since 3pm equals the 24 hour clock value of 15 which is divisible by 5 Execute every hour divisible by 3 and every hour during office hours 8am 5pm 2 5 4 Timezones By default the current local timezone is used but you can also set a specific timezone by enabling the CELERY ENABLE UTC CELERY_TIMEZONE Europe London CELERY_ENABLE_UTC setting and configuring the CELERY_TIMEZONE setting Django Users For Django users the timezone specified in the TIME_ ting CELERY_ENABLE_UTC setting is enabled ZONE setting will be used but not if the set Celery is also compatible with the new USE_TZ setting introduced in Django 1 4 Note The pytz library is recommended when setting a default timezone If pyt z is not installed it will fallback to the mod dateutil library which depends on a system timezone file being available for the timezone selected Timezone definitions change frequently so for the best results an up to date pyt z installation should be used 2 5 5 Starting celerybeat To start the celerybeat service 52 Chapter 2 User Guide Celery Documeniation Release 2 5 5
373. or replies and limit is the maximum number of replies to get By default it will wait for as many replies as possible for one second rate_limit task_name destination all reply False timeout 1 limit 0 Worker returns ok message on success or failure message on failure gt gt gt from celery task control import rate_limit ping destination all reply False timeout 1 limit 0 Worker returns the simple message pong gt gt gt from celery task control import ping gt gt gt ping reply 1e workerl p revoke destination all reply False timeout 1 limit 0 Worker simply returns True gt gt gt from celery task control import revoke gt gt gt revoke 419e46eb cf6a 4271 86a8 442b7124132c reply e workerl True True e You can now add your own remote control commands Remote control commands are functions registered in the command registry Registering a command is done using celery worker control Panel register from celery task control import Panel Panel register def reset_broker_connection panel x kwargs panel consumer reset_connection return ok connection re established With this module imported in the worker you can launch the command using cel ery task control broadcast gt gt gt from celery task control import broadcast gt gt gt broadcast reset_broker_connection reply True
374. ore 2 2 Contributed by Dan McGee The CELERYBEAT_MAX_LOOP_INTERVAL setting was not respected inspect registered_tasks renamed to inspect registered for naming consistency The previous name is still available as an alias Contributed by Mher Movsisyan Worker logged the string representation of args and kwargs without safe guards Issue 480 RHEL init script Changed celeryd startup priority The default start stop priorities for MySQL on RHEL are chkconfig 64 36 Therefore if Celery is using a database as a broker message store it should be started after the database is up and running otherwise errors will ensue This commit changes the priority in the init script to chkconfig 85 15 which are the default recommended settings for 3 rd party applications and assure that Celery will be started after the database service amp shut down before it terminates Contributed by Yury V Zaytsev Key ValueStoreBackend get_many did not respect the timeout argument Issue 512 celerybeat celeryev s workdir option did not chdir before after configuration was attempted Issue 506 After deprecating 2 4 support we can now name modules correctly since we can take use of absolute imports Therefore the following internal modules have been renamed celery concurrency evlet gt celery concurrency eventlet celery concurrency evg gt cel ery concurrency gevent AUTHORS file is now sorted alphabetica
375. org pypi redis To install the redis package use pip or easy_install pip install redis This backend requires the following configuration directives to be set CELERY_REDIS_HOST Host name of the Redis database server e g localhost CELERY_REDIS_PORT Port to the Redis database server e g 6379 CELERY_REDIS_DB Database number to use Default is 0 CELERY_REDIS_PASSWORD Password used to connect to the database 92 Chapter 3 Configuration and defaults Celery Documeniation Release 2 5 5 CELERY_REDIS_MAX_CONNECTIONS Maximum number of connections available in the Redis connection pool used for sending and retrieving results Example configuration CELERY_RESULT_BACKEND redis CELERY_REDIS_HOST localhost CELERY_REDIS_PORT 6379 CELERY_REDIS_DB 0 3 2 11 MongoDB backend settings Note The MongoDB backend requires the pymongo library http github com mongodb mongo python driver tree master CELERY_MONGODB_BACKEND_SETTINGS This is a dict supporting the following keys e host Host name of the MongoDB server Defaults to localhost e port The port the MongoDB server is listening to Defaults to 27017 e user User name to authenticate to the MongoDB server as optional e password Password to authenticate to the MongoDB server optional e database The database name to connect to Defaults to celery e taskmeta_collection The
376. orkers should run as an unprivileged user CELERYD_USER celery CELERYD_GROUP celery Name of the projects settings module export DJANGO_SETTINGS_MODULE settings Example Django configuration Using Virtualenv In case you are using virtualenv you should add the path to your environment s python interpreter Name of nodes to start here we have a single node CELERYD_NODES w1 or we could have three nodes CELERYD_NODES wl w2 w3 T Where to chdir at start CELERYD_CHDIR opt Myproject Python interpreter from environment ENV_PYTHON CELERYD_CHDIR env bin python How to call manage py celeryd_multi CELERYD_MULTI SENV_PYTHON SCELERYD_CHDIR manage py celeryd_multi How to call manage py celeryctl CELERYCTL SENV_PYTHON SCELERYD_CHDIR manage py celeryctl Extra arguments to celeryd CELERYD_OPTS time limit 300 concurrency 8 ame of the celery config module RY_CONFIG_MODULE celeryconfig T CEL ole will be replaced with the nodename RYD_LOG_FILE var log celery n log RYD_PID_FILE var run celery n pid T Et Ed T Workers should run as an unprivileged user CELERYD_USER celery CELERYD_GROUP celery T T Name of the projects settings module export DJANGO_SETTINGS_MODULE setti
377. orts a max_retries argument used to change the default value multiprocessing cpu_count may raise Not Imp lementedError on platforms where this is not supported Is sue 320 Coloring of log messages broke if the logged object was not a string Fixed several typos in the init script documentation A regression caused Task exchange and Task routing_key to no longer have any effect This is now fixed 11 21 2 2 4 187 Celery Documeniation Release 2 5 5 Routing Userguide Fixes typo routers in CELERY_ROUTES must be instances not classes celeryev did not create pidfile even though the pidfile argument was set Task logger format was no longer used Issue 317 The id and name of the task is now part of the log message again A safe version of repr is now used in strategic places to ensure objects with a broken ___repr___ does not crash the worker or otherwise make errors hard to understand Issue 298 Remote control command act ive_queues did not account for queues added at runtime In addition the dictionary replied by this command now has a different structure the exchange key is now a dictionary containing the exchange declaration in full The Q option to celeryd removed unused queue declarations so routing of tasks could fail Queues are no longer removed but rather app amgqp queues consume_from is used as the list of queues to consume from This ensures all queues are available
378. orts broker clustering and HA when used in tributed combination with RabbitMQ You can set up new workers without central configuration e g use your grandma s laptop to help if the queue is temporarily congested Concur Concurrency is achieved by using multiprocessing Eventlet gevent or a mix of these rency Schedul Supports recurring tasks like cron or specifying an exact date or countdown for when ing after the task should be executed Latency Low latency means you are able to execute tasks while the user is waiting Return Task return values can be saved to the selected result store backend You can wait for the Values result retrieve it later or ignore it Result Database MongoDB Redis Cassandra or AMQP message notification Stores Web Your tasks can also be HTTP callbacks enabling cross language communication hooks Rate Supports rate limiting by using the token bucket algorithm which accounts for bursts of limiting traffic Rate limits can be set for each task type or globally for all Routing Using AMQP s flexible routing model you can route tasks to different workers or select different message topologies by configuration or even at runtime Remote Worker nodes can be controlled from remote by using broadcast messaging A range of control built in commands exist in addition to the ability to easily define your own AMQP Redis only Moni You can capture everything happening with the wo
379. orts objects from celery task base and celery task builtins celery task base Contains task base classes Task PeriodicTask TaskSet AsynchronousMapTask ExecuteRemote Task celery task builtins Built in tasks PingTask DeleteExpiredTaskMetaTask 11 51 0 3 7 release date 2008 06 16 11 41 PM CET IMPORTANT Now uses AMQP s basic consume instead of basic get This means we re no longer polling the broker for new messages IMPORTANT Default concurrency limit is now set to the number of CPUs available on the system IMPORTANT tasks register Renamed task_name argument to name so gt gt gt tasks register func task_name mytask has to be replaced with gt gt gt tasks register func name mytask The daemon now correctly runs if the pidlock is stale Now compatible with carrot 0 4 5 Default AMQP connection timeout is now 4 seconds AsyncResult read was always returning True Only use README as long_description if the file exists so easy_install doesn t break celery view JSON responses now properly set its mime type 238 Chapter 11 Change history Celery Documeniation Release 2 5 5 apply_async now has a connection keyword argument so you can re use the same AMQP connection if you want to execute more than one task Handle failures in task_status view such that it won t throw 500s Fixed typo AMQP_SERVER in documentation to AMQP_HOST Worker exception emails sent to administ
380. ory Celery Documeniation Release 2 5 5 e celery conf has been deprecated and modifying celery conf ALWAYS_EAGER will no longer have any effect The default configuration is now available in the celery app defaults module The available configuration options and their types can now be introspected e Remote control commands are now provided by kombu pidbox the generic process mailbox e Internal module celery worker listener has been renamed to celery worker consumer and CarrotListener is now Consumer e Previously deprecated modules celery models and celery management commands have now been removed as per the deprecation timeline e Security Low severity Removed celery task RemoteExecuteTask and accompanying functions dmap dmap_async and execute_remote Executing arbitrary code using pickle is a potential security issue if someone gains unrestricted access to the message broker If you really need this functionality then you would have to add this to your own project e Security Low severity The stats command no longer transmits the broker password One would have needed an authenticated broker connection to receive this password in the first place but sniffing the password at the wire level would have been possible if using unencrypted communication 11 25 2 News e The internal module celery task builtins has been removed e The module celery task schedules is deprecated and celery schedules should be used in
381. ose gt gt gt consumer connection close classmethod BaseTask get_logger loglevel None logfile None propagate False kwargs Get task aware logger object classmethod BaseTask get_publisher connection None exchange None con nect_timeout None exchange_type None options Get a celery task message publisher type TaskPublisher 262 Chapter 12 API Reference Celery Documeniation Release 2 5 5 Warning case you need to close this connection after use gt gt gt publisher get_publisher gt gt gt gt gt gt publisher connection close or used as a context gt gt gt with get_publisher as publisher BaseTask on_failure exc task_id args kwargs einfo Error handler This is run by the worker when the task fails Parameters e exc The exception raised by the task e task_id Unique id of the failed task e args Original arguments for the task that failed e kwargs Original keyword arguments for the task that failed e einfo Except ionInfo instance containing the traceback The return value of this handler is ignored BaseTask on_retry exc task_id args kwargs einfo Retry handler This is run by the worker when the task is to be retried Parameters e exc The exception sent to retry e task_id Unique id of the retried task e args Original arguments for the retried task e kwargs Original keyword arguments fo
382. ould occur while sending error emails Fix contributed by Seong Wun Mun celery bin programs now always defines __ pack age___ as recommended by PEP 366 send_task now emits a warning when used in combination with CELERY_ALWAYS_EAGER Issue 581 Contributed by Mher Movsisyan apply_async now forwards the original keyword arguments to apply when CELERY_ALWAYS_EAGER is enabled celeryev now tries to re establish the connection if the connection to the broker is lost Issue 574 celeryev Fixed a crash occurring if a task has no associated worker information Fix contributed by Matt Williamson The current date and time is now consistently taken from the current loaders now method Now shows helpful error message when given a config module ending in py that can t be imported celeryctl The xpires and eta arguments to the apply command can now be an ISO 8601 formatted string celeryctl now exits with exit status EX_UNAVAILABLE 69 if no replies have been received 168 Chapter 10 What s new in Celery 2 5 CHAPTER 11 Change history 169 Celery Documeniation Release 2 5 5 255 e 2 5 3 2 5 2 News Fixes e 2 5 1 Fixes e 2 5 0 e 2 4 5 e 2 44 Security Fixes Fixes e 2 4 3 e 2 4 2 e 2 4 1 e 2 4 0 Important Notes News e 2 3 4 Security Fixes Fixes 2 3 3 2 3 2 News Fixes 2 3 1
383. outdated so better to move this to Task so it can be used e timer2 Set selfrunning False in stop so it won t try to join again on subsequent calls to stop e Log colors are now disabled by default on Windows e celery platform renamed to celery platforms so it doesn t collide with the built in plat form module e Exceptions occurring in Mediator Pool callbacks are now caught and logged instead of taking down the worker e Redis result backend Now supports result expiration using the Redis EXPIRE command unit tests Don t leave threads running at tear down e celeryd Task results shown in logs are now truncated to 46 chars e Task __name__is now an alias to self __class__ __name__ This way tasks introspects more like regular functions e Task retry Now raises TypeError if kwargs argument is empty See issue 164 e timedelta_seconds Use timedelta total_seconds if running on Python 2 7 e TokenBucket Generic Token Bucket algorithm e celery events state Recording of cluster state can now be paused and resumed including support for buffering State freeze buffer True Pauses recording of the stream If buffer is true events received while being frozen will be buffered and may be replayed later State thaw replay True Resumes recording of the stream If replay is true then the recorded buffer will be applied State freeze_while fun With a function to apply freezes the stream before and replay
384. ow will re use connections and channels and retry sending of the task message if the connection is lost from celery import current_app pool current_app amqp PublisherPool limit 10 def my_view request with pool acquire as publisher add apply_async 2 2 publisher publisher retry 11 26 2 1 4 release date 2010 12 03 12 00 P M CEST 196 Chapter 11 Change history Celery Documeniation Release 2 5 5 11 26 1 Fixes Execution options to apply_async now takes precedence over options returned by active routers This was a regression introduced recently Issue 244 celeryev curses monitor Long arguments are now truncated so curses doesn t crash with out of bounds errors Issue 235 celeryd Channel errors occurring while handling control commands no longer crash the worker but are instead logged with severity error SQLAlchemy database backend Fixed a race condition occurring when the client wrote the pending state Just like the Django database backend it does no longer save the pending state Issue 261 Issue 262 Error email body now uses repr exception instead of str exception as the latter could result in Unicode decode errors Issue 245 Error email timeout value is now configurable by using the EMATL_TIMEOUT setting celeryev Now works on Windows but the curses monitor won t work without having curses Unit test output no longer emits non standard characters celer
385. own 2 tee 18 8 countdown 3 gt gt gt ts run e Got a 3x performance gain by setting the prefetch count to four times the concurrency from an average task round trip of 0 1s to 0 03s A new setting has been added CELERYD_PREFETCH_MULTIPLIER which is set to 4 by default e Improved support for webhook tasks celery task rest is now deprecated replaced with the new and shiny celery task http With more reflective names sensible interface and it s possible to override the methods used to perform HTTP requests e The results of task sets are now cached by storing it in the result backend 11 41 4 Changes e Now depends on carrot gt 0 8 1 e New dependencies billiard python dateutil django picklefield e No longer depends on python daemon e The uuid distribution is added as a dependency when running Python 2 4 e Now remembers the previously detected loader by keeping it in the CELERY_LOADER environment variable This may help on windows where fork emulation is used e ETA no longer sends datetime objects but uses ISO 8601 date format in a string for better compatibility with other platforms e No longer sends error mails for retried tasks e Task can now override the backend used to store results e Refactored the ExecuteWrapper apply and CELERY_ALWAYS_EAGER now also executes the task callbacks and signals e Now using a proper schedu
386. pDispatchTask run url None method GET kwargs url None exception celery task http InvalidResponseError The remote server gave an invalid response class celery task http MutableURL url Object wrapping a Uniform Resource Locator Supports editing the query parameter list You can convert the object back to a string the query will be properly urlencoded Examples gt gt gt url URL http www google com 6580 foo bar x 3 amp y 4 fo0o gt gt gt url query lyfe TAF Fart a CALS Kot a gt gt gt url http www google com 6580 foo bar y 4 amp x 3 f00 gt gt gt url query x 10 gt gt gt url query update George Costanza gt gt gt url exception celery task http RemoteExecuteError The remote task gave a custom error class celery task http URL url dispatcher None HTTP Callback URL Supports requesting an URL asynchronously Parameters e url URL to request e dispatcher Class used to dispatch the request By default this is HttpDispatchTask dispatcher alias of HttpDispatchTask get_async kwargs post_async kwargs exception celery task http UnknownStatusError The remote server gave an unknown status 12 12 celery task http 277 Celery Documentation Release 2 5 5 celery task http extract_response raw_response Extract the response text from a raw JSON response celery task http maybe_ut 8 value Encode to utf 8 only if the va
387. pen if one or more worker processes are killed SQLAlIchemy Result Backend Now returns accidentally removed dat e_done again Issue 325 Task request contex is now always initialized to ensure calling the task function directly works even if it actively uses the request context Exception occuring when iterating over the result from TaskSet app1y fixed eventlet Now properly schedules tasks with an ETA in the past 11 21 2 2 4 release date 2011 02 19 12 00 AM CET 11 21 1 Fixes celeryd 2 2 3 broke error logging resulting in tracebacks not being logged AMQP result backend Polling task states did not work properly if there were more than one result message in the queue TaskSet apply_async and TaskSet apply now supports an optional taskset_id keyword argument Issue 331 The current taskset id if any is now available in the task context as request taskset Issue 329 SQLAlchemy result backend date_done was no longer part of the results as it had been accidentally removed It is now available again Issue 325 SQLAIchemy result backend Added unique constraint on Task task_id and TaskSet taskset_id Tables needs to be recreated for this to take effect Fixed exception raised when iterating on the result of TaskSet apply Tasks Userguide Added section on choosing a result backend 11 22 2 2 3 release date 2011 02 12 04 00 P M CET 11 22 1 Fixes Now depends on Kombu 1 0 3 Task retry now supp
388. perly dropped and that it would be possible to regain supervisor privileges later 11 7 2 Fixes e Processes pool Fixed rare deadlock at shutdown Issue 523 Fix contributed by Ionel Maries Christian e Webhook tasks issued the wrong HTTP POST headers Issue 515 The Content Type header has been changed from application json application x www form urlencoded and adds a proper Content Length header Fix contributed by Mitar e Daemonization cookbook Adds a configuration example using Django and virtualenv together Issue 505 Contributed by Juan Ignacio Catalano e generic init scripts now automatically creates log and pid file directories Issue 545 Contributed by Chris Streeter 11 8 2 4 3 release date 2011 11 22 18 00 P M GMT by Ask Solem e Fixes module import typo in celeryctl Issue 538 Fix contributed by Chris Streeter 11 9 2 4 2 release date 2011 11 14 12 00 P M GMT by Ask Solem e Program module no longer uses relative imports so that itis possible to do python m celery bin name 174 Chapter 11 Change history Celery Documeniation Release 2 5 5 11 10 2 4 1 release date 2011 11 07 06 00 P M GMT by Ask Solem celeryctl inspect commands was missing output processes pool Decrease polling interval for less idle CPU usage processes pool MaybeEncodingError was not wrapped in ExceptionInfo Issue 524 celeryd would silence errors occuring after task consumer started logging
389. picky reader albeit a discouraged one if you can survive without doing it On to the code clickmuncher messaging py from celery messaging import establish_connection from kombu compat import Publisher Consumer from clickmuncher models import Click def send_increment_clicks for_url Send a message for incrementing the click count for an URL connection establish_connection publisher Publisher connection connection exchange clicks routing_key increment_click exchange_type direct publisher send for_url publisher close connection close 146 Chapier 8 Tutorials Celery Documeniation Release 2 5 5 def process_clicks Process all currently gathered clicks by saving them to the database connection establish_connection consumer Consumer connection connection queue clicks exchange clicks routing_key increment_click xchange_type direct clicks_for_url messages_for_url for message in consumer iterqueue url message body clicks_for_url url clicks_for_url get url 0 1 We We if url in messages_for_url messages_for_url url append message else messages_for_url url message one TE IN eT for eacl RL for url click_count in clicks_for_urls items Click objects increment_clicks url click_count t slicks has b een registered for Enis UR acknowledge th messag aCKNOWLE SSAGE m
390. port EventReceiver from celery messaging import establish_connection from celery events state import State from myapp import DumpCam def main state State with establish_connection as connection recv EventReceiver connection handlers state event with DumpCam state freq 1 0 recv capture limit timeout if name s main__ main Event Reference This list contains the events sent by the worker and their arguments Task Events e task sent uuid name args kwargs retries eta xpires Sent when a task message is published and the CELERY_SEND_TASK_SENT_EV enabled ENT setting is e task received uuid name args kwargs retries eta hostnam Sent when the worker receives a task e task started uuid hostname timestamp pid Sent just before the worker executes the task e task succeeded uuid result runtime hostname timestamp e timestamp 74 Chapter 2 User Guide Celery Documeniation Release 2 5 5 Sent if the task executed successfully Runtime is the time it took to execute the task using the pool Starting from the task is sent to the worker pool and ending when the pool result handler callback is called e task failed uuid exception traceback hostname timestamp Sent if the execution of the task failed e task revoked uuid Sent if the task has been revoked Note that this is likely to be sent b
391. pply async entry publisher None kwargs 350 Chapter 13 Internals Celery Documeniation Release 2 5 5 close connection get_schedule info install_default_entries data logger None Current logger max_interval 1 Maximum time to sleep between re checking the schedule maybe_due entry publisher None merge_inplace b publisher reserve entry schedule The schedule dict shelve send_task args kwargs set_schedule schedule setup_schedule should_sync sync sync_every 180 How often to sync the schedule 3 minutes by default tick Run a tick that is one iteration of the scheduler Executes all due tasks update_from_dict dict_ exception celery beat SchedulingError An error occured while scheduling a task class celery beat Service logger None max_interval None schedule_filename None sched uler_cls None app None get_scheduler lazy False scheduler scheduler_cls alias of PersistentScheduler start embedded_process False stop wait False sync 13 6 Internal Module Reference 351 Celery Documeniation Release 2 5 5 13 6 21 celery backends celery backends get_backend_cls args kwargs Get backe nd class by name alias 13 6 22 celery backends base celery backends base class celery backends base BaseBackend args kwargs Base backend class EXCEPTION_STATES frozenset FAILURE RETRY REVO
392. r any custom serialization methods that have been registered with kombu serialization registry Please see Serializers for more information Task backend The result store backend to use for this task Defaults to the CELERY_RESULT_BACKEND setting 2 2 Tasks 23 Celery Documeniation Release 2 5 5 Task acks_late If set to True messages for this task will be acknowledged after the task has been executed not just before which is the default behavior Note that this means the task may be executed twice if the worker crashes in the middle of execution which may be acceptable for some applications The global default can be overridden by the CELERY_ACKS_LATE setting Task track_started If True the task will report its status as started when the task is executed by a worker The default value is False as the normal behaviour is to not report that level of granularity Tasks are either pending finished or waiting to be retried Having a started status can be useful for when there are long running tasks and there is a need to report which task is currently running The host name and process id of the worker executing the task will be available in the state metadata e g result info pid The global default can be overridden by the CELERY_TRACK_STARTED setting See also The API reference for BaseTask Message and routing options Task queue
393. r making sure the world is how it should be If you have a task that re indexes a search engine and the search engine should only be re indexed at maximum every 5 minutes then it must be the tasks responsibility to assert that not the callers Another gotcha is Django model objects They shouldn t be passed on as arguments to tasks It s almost always better to re fetch the object from the database when the task is running instead as using old data may lead to race conditions Imagine the following scenario where you have an article and a task that automatically expands some abbreviations in it class Article models Model title models CharField body models TextField task def expand_abbreviations article article body replace MyCorp My Corporation article save First an author creates an article and saves it then the author clicks on a button that initiates the abbreviation task gt gt gt article Article objects get id 102 gt gt gt expand_abbreviations delay model_object Now the queue is very busy so the task won t be run for another 2 minutes In the meantime another author makes changes to the article so when the task is finally run the body of the article is reverted to the old version because the task had the old body in its argument Fixing the race condition is easy just use the article id instead and re fetch the article in the task body 34 Chapter 2 User Guide Celery Do
394. r more details celery utils patch ensure_process_aware_logger 13 6 51 celery utils serialization e celery utils serialization j celery utils serialization Utilities for safely pickling exceptions copyright 3 2009 2012 by Ask Solem license BSD see LICENSE for more details exception celery utils serialization UnpickleableExceptionWrapper exc_module exc_cls_name exc_args text None Wraps unpickleable exceptions Parameters e exc_module see exc_module e exc_cls_name see exc_cls_name 13 6 Internal Module Reference 383 Celery Documentation Release 2 5 5 e exc_args see exc_args Example gt gt gt try ae something_raising_unpickleable_exc gt gt gt except Exception e exc UnpickleableException e __class__ __module__ e __class__ __name__ e args pickle dumps exc exc_args None The arguments for the original exception exc_cls_name None The name of the original exception class exc_module None The module of the original exception classmethod from_exception exc restore celery utils serialization create_exception_cls name module parent None Dynamically create an exception class celery utils serialization find_nearest_pickleable_exception exc With an exception instance iterate over its super classes by mro and find the first super exception that is pickleable It does not go below Exception i e it skips Exc
395. r or day depending on the period of the timedelta If relative is true the frequency is not rounded and will be relative to the time when celerybeat was started 2 5 3 Crontab schedules If you want more control over when the task is executed for example a particular time of day or day of the week you can use the crontab schedule type from celery schedules import crontab CELERYBEAT_ SCHEDULE every monday morning task tasks add schedule crontab hour 7 minute 30 day_of_week 1 Merges T6 26 br The syntax of these crontab expressions are very flexible Some examples 2 5 Periodic Tasks 51 Celery Documentation Release 2 5 5 Example crontab crontab minute 0 hour 0 crontab minute 0 hour 3 crontab minute 0 hour 0 3 6 9 12 15 18 21 crontab minute 15 crontab day_of_week sunday crontab minute hour day_of_week sun crontab minute 10 hour 3 17 22 day_of_week thu fri crontab minute 0 hour 2 3 crontab minute 0 hour 5 crontab minute 0 hour 3 8 17 Meaning Execute every minute Execute daily at midnight Execute every three hours 3am 6am 9am noon 3pm 6pm 9pm Same as previous Execute every 15 minutes Execute every minute at Sundays Same as previous Execute every ten minutes but only between 3 4 am 5 6 pm and 10 11 pm on Thursdays
396. r the retried task e einfo Except ionInfo instance containing the traceback The return value of this handler is ignored BaseTask on_success retval task_id args kwargs Success handler Run by the worker if the task executes successfully Parameters e retval The return value of the task e task_id Unique id of the executed task e args Original arguments for the executed task e kwargs Original keyword arguments for the executed task The return value of this handler is ignored If you don t specify a connection one will automatically be established for you in that 12 6 celery task base 263 Celery Documentation Release 2 5 5 classmethod BaseTask retry args None kwargs None exc None throw True eta None countdown None max_retries None options Retry the task Parameters e args Positional arguments to retry with e kwargs Keyword arguments to retry with e exc Optional exception to raise instead of MaxRetriesExceededError when the max restart limit has been exceeded e countdown Time in seconds to delay the retry for e eta Explicit time and date to run the retry at must be a dat et ime instance e max_retries If set overrides the default retry limit e options Any extra options to pass on to meth apply_async e throw If this is False do not raise the RetryTaskError exception that tells the worker to mark
397. r username password User objects create username username password password Task options are added as arguments to task task serializer json def create_user username password User objects create username username password password 2 2 2 Context task request contains information and state related the currently executing task and must always contain the following attributes id The unique id of the executing task taskset The unique id of the taskset this task is a member of if any args Positional arguments kwargs Keyword arguments retries How many times the current task has been retried An integer starting at 0 is_eager Set to True if the task is executed locally in the client and not by a worker logfile The file the worker logs to See Logging loglevel The current log level used hostname Hostname of the worker instance executing the task delivery_info Additional message delivery information This is a mapping containing the exchange and rout ing key used to deliver this task Used by e g ret ry to resend the task to the same destina tion queue NOTE As some messaging backends don t have advanced routing capabilities you can t trust the availability of keys in this mapping Example Usage from celery task import task task def add x y print Executing task id r args sr kwargs Sr add request id add request args add request kwargs 2 2 3 Logging You ca
398. rators now works properly No longer depends on django so installing celery won t affect the preferred Django version installed Now works with PostgreSQL psycopg2 again by registering the PickledObject field celeryd Added detach option as an alias to daemon and it s the term used in the documentation from now on Make sure the pool and periodic task worker thread is terminated properly at exit So Ctrl C works again Now depends on python daemon Removed dependency to simplejson Cache Backend Re establishes connection for every task process if the Django cache backend is mem cached libmemcached Tyrant Backend Now re establishes the connection for every task executed 11 52 0 3 3 release date 2009 06 08 01 07 P M CET e The PeriodicWorkController now sleeps for 1 second between checking for periodic tasks to execute 11 53 0 3 2 release date 2009 06 08 01 07 PM CET e celeryd Added option discard Discard delete all waiting messages in the queue e celeryd The wakeup after option was not handled as a float 11 54 0 3 1 release date 2009 06 08 01 07 PM CET e The PeriodicTask worker is now running in its own thread instead of blocking the TaskController loop e Default QUEUE_WAKEUP_AFTER has been lowered to 0 7 was 0 3 11 55 0 3 0 release date 2009 06 08 12 41 P M CET 11 52 0 3 3 239 Celery Documentation Release 2 5 5 VERY IMPORTANT Pickle is now the encoder used for
399. re are several built in backends to choose from SQLAIchemy Django ORM Memcached Redis AMQP MongoDB Tokyo Tyrant and Redis or you can define your own No backend works well for every use case You should read about the strengths and weaknesses of each backend and choose the most appropriate for your needs See also Task result backend settings AMQP Result Backend The AMQP result backend is special as it does not actually store the states but rather sends them as messages This is an important difference as it means that a result can only be retrieved once If you have two processes waiting for the same result one of the processes will never receive the result Even with that limitation it is an excellent choice if you need to receive state changes in real time Using messaging means the client does not have to poll for new states There are several other pitfalls you should be aware of when using the AMQP backend 26 Chapter 2 User Guide Celery Documeniation Release 2 5 5 e Every new task creates a new queue on the server with thousands of tasks the broker may be overloaded with queues and this will affect performance in negative ways If you re using RabbitMQ then each queue will be a separate Erlang process so if you re planning to keep many results simultaneously you may have to increase the Erlang process limit and the maximum number of file descriptors your OS allows e Old results will
400. red in memory only and is lost if the server dies or restarts 2 or persistent default The message is persistent Which means the message is stored both in memory and on disk and therefore preserved if the server dies or restarts The default value is 2 persistent arguments Additional arguments to specify when the exchange is declared Message body delivery_mode None priority None content_type None con tent_encoding None properties None headers None Create message instance to be sent with publish Parameters e body Message body e delivery mode Set custom delivery mode Defaults to delivery_mode e priority Message priority 0 to 9 currently not supported by Rab bitMQ e content_type The messages content_type If content_type is set no serialization occurs as it is assumed this is either a binary object or you ve done your own serialization Leave blank if using built in serialization as our library properly sets content_type 358 Chapter 13 Internals Celery Documeniation Release 2 5 5 e content_encoding The character set in which this object is encoded Use binary if sending in raw binary objects Leave blank if using built in serialization as our library properly sets content_encoding e properties Message properties e headers Message headers PERSISTENT_DELIVERY_MODE 2 TRANSIENT_DELIVERY_MODE 1 attrs name None type None
401. red in the Kombu compression registry The default is to send uncompressed messages CELERY_TASK_RESULT_EXPIRES Time in seconds or a t imedelta object for when after stored task tombstones will be deleted A built in periodic task will delete the results after this time celery task backend_cleanup Note For the moment this only works with the amqp database cache redis and MongoDB backends When using the database or MongoDB backends celerybeat must be running for the results to be expired CELERY_MAX_CACHED_RESULTS Result backends caches ready results used by the client This is the total number of results to cache before older results are evicted The default is 5000 CELERY_TRACK_STARTED If True the task will report its status as started when the task is executed by a worker The default value is False as the normal behaviour is to not report that level of granularity Tasks are either pending finished or waiting to be retried Having a started state can be useful for when there are long running tasks and there is a need to report which task is currently running CELERY_TASK_SERIALIZER A string identifying the default serialization method to use Can be pickle default json yaml msgpack or any custom serialization methods that have been registered with kombu serialization registry See also Serializers CELERY_TASK_PUBLISH_RETRY New in version 2 2 Decides if publishing task messages
402. report an issue and to ensure a timely response is to use the issue tracker 1 Create a GitHub account You need to create a GitHub account to be able to create new issues and participate in the discussion 2 Determine if your bug is really a bug You should not file a bug if you are requesting support For that you can use the Mailing list or IRC 3 Make sure your bug hasn t already been reported Search through the appropriate Issue tracker If a bug like yours was found check if you have new information that could be reported to help the developers fix the bug 4 Collect information about the bug To have the best chance of having a bug fixed we need to be able to easily reproduce the conditions that caused it Most of the time this information will be from a Python traceback message though some bugs might be in design spelling or other errors on the website docs code If the error is from a Python traceback include it in the bug report We also need to know what platform you re running Windows OSX Linux etc the version of your Python inter preter and the version of Celery and related packages that you were running when the bug occurred 5 Submit the bug By default GitHub will email you to let you know when new comments have been made on your bug In the event you ve turned this feature off you should check back on occasion to ensure you don t miss any questions a developer trying to fix the bug might ask
403. rgument list followed by for example celerybeat l info celerybeat max_loop_interval 10 0 Now limits the number of frames in a traceback so that celeryd does not crash on maximum recursion limit exceeded exceptions Issue 615 The limit is set to the current recursion limit divided by 8 which is 125 by default To get or set the current recursion limit use sys getrecursionlimit and sys setrecursionlimit More information is now preserved in the pickleable traceback This has been added so that Sentry can show more details Contributed by Sean O Connor CentOS init script has been updated and should be more flexible Contributed by Andrew McFague MongoDB result backend now supports forget Contributed by Andrew McFague task retry now re raises the original exception keeping the original stack trace Suggested by ojii The uid argument to daemons now uses initgroups to set groups to all the groups the user is a member of Contributed by Lukasz Oles celeryctl Added she11 command The shell will have the current_app celery and all tasks automatically added to locals celeryctl Added migrate command The migrate command moves all tasks from one broker to another Note that this is experimental and you should have a backup of the data before proceeding Examples celeryctl migrate redis localhost amqp localhost celeryctl migrate amgqp localhost vl amqp localhost v2 python manage py c
404. rgv index 0 celery bin celeryct1 command fun name None celery bin celeryctl determine_exit_status ret class celery bin celeryct1 help app None no_color False run args kwargs usage command celery bin celeryctl indent s n 4 class celery bin celeryctl inspect app None no_color False choices scheduled 1 0 reserved 1 0 registered 1 0 active 1 0 cancel_consumer 1 0 active_queues 1 0 option_list lt Option at 0x5c213f8 app gt lt Option at Ox5acf950 b broker gt lt Option at Ox5acf998 loader gt lt C run args kwargs say direction title body show_body True usage command class celery bin celeryctl list_ app None no_color False args lt bindings gt list_bindings channel run what None _ kw celery bin celeryctl main class celery bin celeryct1l migrate app None no_color False on_migrate_task state body message run args kwargs usage command class celery bin celeryct1 purge app None no_color False run args kwargs class celery bin celeryct1l result app None no_color False args lt task_id gt option_list lt Option at 0x5c213f8 app gt lt Option at 0x5acf950 b broker gt lt Option at 0x5acf998 loader gt lt C run task_id args kwargs 12 36 celeryctl celery bin celeryctl 303 Celery Documentatio
405. rker Pool w autoscale None kwargs The pool component Describes how to initialize the worker pool and starts and stops the pool during worker startup shutdown Adds attributes eautoscale pool max_concurrency min_concurrency create w name pool namespace worker requires queues class celery worker Queues parent kwargs This component initializes the internal queues used by the worker create w name queues namespace worker class celery worker StateDB w kwargs This component sets up the workers state db if enabled create w name state db namespace worker class celery worker Timers parent kwargs This component initializes the internal timers used by the worker create w name timers namespace worker requires pool class celery worker WorkController loglevel None hostname None logger None ready_callback lt function noop at OxIcaf66S gt queues None app None kwargs Unmanaged worker instance CLOSE 2 RUN 1 TERMINATE 3 autoreloader_cls None autoscaler_cls None concurrency None consumer_cls None disable rate limits None 326 Chapter 13 Internals Celery Documeniation Release 2 5 5 eta_scheduler_cls None eta_scheduler_precision None force_execv None logfile None loglevel 40 max_tasks_per_child None mediator_cls None on_timer_error einfo on_
406. rker_init eWhat modules are imported to find tasks builtin_modules frozenset celery task cmdline _config_parser args namespace celery re_type lt _sre SRE_Pattern object at Ox1c9f990 gt extra_types json lt function loads at 0x1d12938 gt override_types dict json list json tuple json conf Loader configuration config_from_envvar variable_name silent False config _from_object obj silent False configured False error_envvar_not_set The environment variable r is not set nand as such the configuration could not be loade import_default_modules import_from_cwd module imp None package None import_module module package None import_task_module module init_worker init_worker_process mail mail_admins subject body fail_silently False sender None to None host None port None user None password None timeout None use_ssl False use_tls False now utc True on_process_cleanup This method is called after a task is executed on_task_init task_id task This method is called before a task is executed on_worker_ init This method is called when the worker celeryd starts on_worker_process_init This method is called when a child process starts override _backends worker initialized False 12 21 celery loaders base 285 Celery Documentation Release 2 5 5 12 22 celery registry e
407. rkers in real time by subscribing to toring events A real time web monitor is in development Serial Supports Pickle JSON YAML or easily defined custom schemes One task invocation ization can have a different scheme than another Trace Errors and tracebacks are stored and can be investigated after the fact backs UUID Every task has an UUID Universally Unique Identifier which is the task id used to query task status and return value Retries Tasks can be retried if they fail with configurable maximum number of retries and delays between each retry Task A Task set is a task consisting of several sub tasks You can find out how many or if all of Sets the sub tasks has been executed and even retrieve the results in order Progress bars anyone Made You can query status and results via URLs enabling the ability to poll task status using for Web Ajax Error Can be configured to send emails to the administrators when tasks fails Emails 1 1 5 Documentation Documentation for the production version can be found here http docs celeryproject org en latest and the documentation for the development version can be found here http celery github com celery 1 1 Introduction 5 Celery Documentation Release 2 5 5 1 1 6 Installation You can install Celery either via the Python Package Index PyPI or from source To install using pip pip install U Celery To install using easy_install
408. rl example com eta 2010 06 07 09 07 52 priority 0 request name tasks sleeptask id la7980ea 8b19 413e 91d2 0b74 3844c4a Targas 1 kwargs eta 2010 06 07 09 07 53 priority 0 request name tasks sleeptask id 49661b9a aa22 4120 94b7 9ee8031d219d args 2 kwargs Note that these are tasks with an eta countdown argument not periodic tasks Dump of reserved tasks Reserved tasks are tasks that has been received but is still waiting to be executed You can get a list of these using reserved gt gt gt i reserved workerl example com name tasks sleeptask id 32666e9b 809c 41fa 8e93 5ae0c80afbbt args 8 kwargs 2 4 Workers Guide 49 Celery Documentation Release 2 5 5 2 5 Periodic Tasks e Introduction e Entries Available Fields e Crontab schedules e Timezones e Starting celerybeat Using custom scheduler classes 2 5 1 Introduction celerybeat is a scheduler It kicks off tasks at regular intervals which are then executed by the worker nodes available in the cluster By default the entries are taken from the CELERYBEAT_SCHEDULE setting but custom stores can also be used like storing the entries in an SQL database You have to ensure only a single scheduler is running for a schedule at a time otherwise you would end up with dupl
409. rns Parameters e status Current task state e retval Task return value exception e task_id Unique id of the task e args Original arguments for the task that failed e kwargs Original keyword arguments for the task that failed e einfo ExceptionInfo instance containing the traceback if any The return value of this handler is ignored 30 Chapter 2 User Guide Celery Documeniation Release 2 5 5 on_failure self exc task_id args kwargs einfo This is run by the worker when the task fails Parameters e exc The exception raised by the task e task_id Unique id of the failed task e args Original arguments for the task that failed e kwargs Original keyword arguments for the task that failed e einfo ExceptionInfo instance containing the traceback The return value of this handler is ignored on_retry self exc task_id args kwargs einfo This is run by the worker when the task is to be retried Parameters e exc The exception sent to retry e task_id Unique id of the retried task e args Original arguments for the retried task e kwargs Original keyword arguments for the retried task e einfo ExceptionInfo instance containing the traceback The return value of this handler is ignored on_success self retval task_id args kwargs Run by the worker if the task executes successfully Parameters e retval The return
410. rocessing on FreeBSD isn t that easy but thanks to Viktor Petersson we now have a step to step guide http www playingwithwire com 2009 10 how to get celeryd to work on freebsd 7 2 37 Web based 3D animation software Indy Chang Liu at ThinkingCactus uses Celery to render animations asynchronously PDF http ojs pythonpapers org index php tppm article viewFile 105 122 140 Chapter 7 Community Resources Celery Documeniation Release 2 5 5 7 2 38 Queued Storage Backend for Django http stepsandnumbers com archive 2010 01 04 queued storage backend for django 7 2 39 RabbitMQ with Python and Ruby http www slideshare net hungryblank rabbitmq with python and ruby rupy 2009 7 2 News 141 Celery Documeniation Release 2 5 5 142 Chapter 7 Community Resources CHAPTER 8 Tutorials Release 2 5 Date February 04 2014 8 1 Using Celery with Redis Database as the messaging queue 8 1 1 Redis This section has been moved to Using Redis 8 1 2 SQLAIchemy This section has been moved to Using SQLAlchemy 8 1 3 Django Database This section has been moved to Using the Django Database 8 2 Debugging Tasks Remotely using pdb 8 2 1 Basics celery contrib rdb is an extended version of pdb that enables remote debugging of processes that does not have terminal access Example usage from celery contrib import rdb from celery task import task task def add x y result x y rdb set
411. roker connection to use if not set a connection will be established automatically connect_timeout Timeout for new connection if a custom connection is not provided e reply Wait for and return the reply e timeout Timeout in seconds to wait for the reply limit Limit number of replies Control rate_limit task_name rate_limit destination None kwargs Set rate limit for task by type Parameters e task_name Name of task to change rate limit for e rate_limit The rate limit as tasks per second or a rate limit string 00 m etc see celery task base Task rate_limit for more information 274 Chapter 12 API Reference Celery Documeniation Release 2 5 5 destination If set a list of the hosts to send the command to when empty broadcast to all workers connection Custom broker connection to use if not set a connection will be established automatically connect_timeout Timeout for new connection if a custom connection is not provided reply Wait for and return the reply timeout Timeout in seconds to wait for the reply limit Limit number of replies Control revoke task_id destination None terminate False signal SIGTERM kwargs Revoke a task by id If a task is revoked the workers will ignore the task and not execute it after all Parameters task_id Id of the task to revoke terminate Also terminate the process currently workin
412. ry bi n cel eryctl cel ery bi n cel eryd cel ery bi n cel eryd_multi cel n cel cel cel cel cel cel cel cel cel cel cel cel cel ery bi lery concu lery concu lery concu lery concu lery concu lery concu lery concu lery concu eryev rrency rrency base rrency eventlet rrency gevent rrency processes rrency processes pool rrency solo rrency threads lery contrib abortable lery contrib batches lery contrib migrate lery contrib rdb cel lery datas tructures ce ce ce ce ce ce ce ce lery db models lery db session Lery events lery events cursesmon lery events dumper lery events snapshot xecut lery events state 29 lery exceptions io ce ce ce ce ce ce ce ce ce ce ce ce ce ce ce ce ce ce ce ce ce ce ce ce ce ce ce ce ce ce ce ce lery Lery u Lery u Lery u Lery u Lery u Lery u Lery u Lery u Lery u Lery u lery loaders lery loaders app lery loaders base lery loaders default lery log lery platforms lery registry lery result lery routes lery schedules lery security lery security certificate lery security key lery security serialization CEE ei til til ti til tid
413. ry_info kwargs task_retries self request retries kwargs logfile self request logfile kwargs loglevel self request loglevel kwargs task_is_eager self request is_eager NEW self request args NEW self request kwargs In addition the following methods now automatically uses the current context so you don t have to pass kwargs manually anymore task retry task get_logger task update_state e Eventlet support This is great news for I O bound tasks To change pool implementations you use the P poo1 argument to celeryd or globally using the CELERYD_POOL setting This can be the full name of a class or one of the following aliases processes eventlet gevent For more information please see the Concurrency with Eventlet section in the User Guide Why not gevent 190 Chapter 11 Change history Celery Documeniation Release 2 5 5 For our first alternative concurrency implementation we have focused on Eventlet but there is also an experimental gevent pool available This is missing some features notably the ability to schedule ETA tasks Hopefully the gevent support will be feature complete by version 2 3 but this depends on user de mand and contributions e Python 2 4 support deprecated We re happy H H H H Hsad to announce that this is the last version to support Python 2 4 You are urged to make some noise if you re currently
414. ryev celery events snapshot evcam celery events snapshot Polaroid celery events EventReceiver celery events cursesmon evtop x celery events EventReceiver x celery events cursesmon CursesMonitor celery events dumper celery events EventReceiver e celery bin celeryctl celeryctl celery bin celeryctl Command e celery bin caqmadm AMQPAdmin e celery bin celerybeat BeatCommand celery apps beat Beat x celery beat Service celery beat Scheduler 13 6 Internal Module Reference Release 2 5 Date February 04 2014 13 6 1 celery abstract e celery abstract I celery abstract Implements components and boot steps copyright 3 2009 2012 by Ask Solem license BSD see LICENSE for more details 13 6 Internal Module Reference 323 Celery Documeniation Release 2 5 5 class celery abstract Component parent kwargs A component The __init___ method is called when the component is bound to a parent object and can as such be used to initialize attributes in the parent object at parent instantiation time abstract None if set the component will not be registered but can be used as a component base class create parent Create the component enabled True This provides the default for include_if include parent include_if parent An optional predicate that decided whether this component should be created instantiate qualname args kwargs last False This flag is
415. s RabbitMQ versions 2 1 0 or higher CELERY_TASK_ERROR_WHITELIST Deprecated since version 2 5 A white list of exceptions to send error emails for This option is pending deprecation and is scheduled for removal in version 3 0 CELERYD_LOG_FILE Deprecated since version 2 4 This option is deprecated and is scheduled for removal in version 3 0 Please use the logfile argument instead The default file name the worker daemon logs messages to Can be overridden using the logfile option to celeryd 106 Chapter 3 Configuration and defaults Celery Documeniation Release 2 5 5 The default is None stderr CELERYD_LOG_LEVEL Deprecated since version 2 4 This option is deprecated and is scheduled for removal in version 3 0 Please use the logleve1 argument instead Worker log level can be one of DEBUG INFO WARNING ERROR or CRITICAL Can also be set via the loglevel argument to celeryd See the logging module for more information CELERYBEAT_LOG_FILE Deprecated since version 2 4 This option is deprecated and is scheduled for removal in version 3 0 Please use the logfile argument instead The default file name to log messages to Can be overridden using the logfile option to celerybeat The default is None stderr CELERYBEAT_LOG_LEVEL Deprecated since version 2 4 This option is deprecated and is scheduled for removal in version 3 0 Please use the loglevel argument instead Loggi
416. s according to the run time see Routing Tasks Reserve one task at a time When using early acknowledgement default a prefetch multiplier of 1 means the worker will reserve at most one extra task for every active worker process When users ask if it s possible to disable prefetching of tasks often what they really want is to have a worker only reserve as many tasks as there are child processes But this is not possible without enabling late acknowledgements acknowledgements A task that has been started will be retried if the worker crashes mid execution so the task must be idempotent see also notes at Should I use retry or acks_late You can enable this behavior by using the following configuration options CELERY_ACKS_LATE CELERYD_PREFETCH MULTIPLIER 1 Rate Limits The system responsible for enforcing rate limits introduces some overhead so if you re not using rate limits it may be a good idea to disable them completely This will disable one thread and it won t spend as many CPU cycles when the queue is inactive Set the CELERY_DISABLE_RATE_LIMITS setting to disable the rate limit subsystem CELERY_DISABLE_RATE LIMITS 2 12 Concurrency Release 2 5 Date February 04 2014 2 12 1 Concurrency with Eventlet Introduction The Eventlet homepage describes it as A concurrent networking library for Python that allows you to
417. s for more information New BROKER_TRANSPORT_OPTIONS setting can be used to pass additional arguments to a particular broker transport celeryd worker_pidis now part of the request info as returned by broadcast commands TaskSet apply Taskset apply_async now accepts an optional taskset_id argument The taskset_id if any is now available in the Task request context SQLAIchemy result backend taskset_id and taskset_id columns now have a unique constraint Tables need to recreated for this to take affect Task Userguide Added section about choosing a result backend Removed unused attribute AsyncResult uuid 11 20 3 Fixes e multiprocessing Pool Fixes race condition when marking job with WorkerLostError Issue 268 The process may have published a result before it was terminated but we have no reliable way to detect that this is the case So we have to wait for 10 seconds before marking the result with WorkerLostError This gives the result handler a chance to retrieve the result e multiprocessing Pool Shutdown could hang if rate limits disabled 11 20 2 2 5 185 Celery Documeniation Release 2 5 5 There was a race condition when the MainThread was waiting for the pool semaphore to be released The ResultHandler now terminates after 5 seconds if there are unacked jobs but no worker processes left to start them it needs to timeout because there could still be an ack result that we haven t consum
418. s on all supported Python versions Building the documentation Verifying your contribution pyflakes amp PEP8 x API reference e Coding Style e Contacts Committers Ask Solem x Mher Movsisyan Steeve Morin Website x Mauro Rocco Jan Henrik Helmers Packages celery kombu billiard librabbitmq celerymon django celery cl cyme Deprecated e Release Procedure Updating the version number Releasing Updating bundles 120 Chapter 6 Contributing Celery Documeniation Release 2 5 5 6 1 Community Code of Conduct The goal is to maintain a diverse community that is pleasant for everyone That is why we would greatly appreciate it if everyone contributing to and interacting with the community also followed this Code of Conduct The Code of Conduct covers our behavior as members of the community in any forum mailing list wiki website Internet relay chat IRC public meeting or private correspondence The Code of Conduct is heavily based on the Ubuntu Code of Conduct and the Pylons Code of Conduct 6 1 1 Be considerate Your work will be used by other people and you in turn will depend on the work of others Any decision you take will affect users and colleagues and we expect you to take those consequences into account when making decisions Even if it s not obvious at the time our contributions to Ubuntu will impact the work of others For example chang
419. s the buffer after the function returns e EventReceiver capture Now supports a timeout keyword argument e celeryd The mediator thread is now disabled if CELERY_RATE_LIMITS is enabled and tasks are directly sent to the pool without going through the ready queue Optimization 11 30 3 Fixes e Pool Process timed out by TimeoutHandler must be joined by the Supervisor so don t remove it from the internal process list See issue 192 e TaskPublisher delay_task now supports exchange argument so exchange can be overridden when sending tasks in bulk using the same publisher 204 Chapter 11 Change history Celery Documeniation Release 2 5 5 See issue 187 e celeryd no longer marks tasks as revoked if CELERY_IGNORE_RESULT is enabled See issue 207 e AMQP Result backend Fixed bug with result get if CELERY_TRACK_STARTED enabled result get would stop consuming after receiving the STARTED state e Fixed bug where new processes created by the pool supervisor becomes stuck while reading from the task Queue See http bugs python org issue 10037 e Fixed timing issue when declaring the remote control command reply queue This issue could result in replies being lost but have now been fixed e Backward compatible LoggerAdapter implementation Now works for Python 2 4 Also added support for several new methods fatal makeRecord _log log isEnabledFor addHan
420. serializer To make sure that your exceptions are pickleable the exception MUST provide the original arguments it was instantiated with in its args attribute The simplest way to ensure this is to have the exception call Exception __init__ Let s look at some examples that work and one that doesn t class HttpError Exception pass class HttpError Exception def init s status_code status_code status_code class HttpError Exception 28 Chapter 2 User Guide Celery Documeniation Release 2 5 5 def init E Status_code status_code status_code Exception init__ self status_code So the rule is For any exception that supports custom arguments xargs Exception __init__ self xargs must be used There is no special support for keyword arguments so if you want to preserve keyword arguments when the exception is unpickled you have to pass them as regular args class HttpError Exception def init status_code headers 1e body 3s status_code status_code headers headers body body HttpError __init__ status_code headers body 2 2 9 Creating custom task classes All tasks inherit from the celery task Task class The task s body is its run method The following code task def add x y return x y will do roughly this behind the scenes task class AddTask Task def run self x y return x y add registry tasks AddTask na
421. ses pool ResultHandler outqueue get cache poll join_exited_workers putlock body class celery concurrency processes pool Supervisor pool body class celery concurrency processes pool TaskHandler taskqueue put outqueue pool body class celery concurrency processes pool ThreadPool processes None _ initializer None initargs class DummyProcess group None target None name None args kwargs exitcode start 344 Chapter 13 Internals Celery Documeniation Release 2 5 5 ThreadPool Process alias of DummyProcess class celery concurrency processes pool TimeoutHandler processes cache t_soft body t_hard exception celery concurrency processes pool WorkersJoined All workers have terminated celery concurrency processes pool celery concurrency processes pool celery concurrency processes pool celery concurrency processes pool celery concurrency processes pool error msg args kwargs Mapstar args safe_apply_callback fun args soft_timeout_sighandler signum frame worker inqueue outqueue initializer None initargs maxtasks None sentinel None 13 6 16 celery concurrency eventlett experimental class celery concurrency eventlet Schedule args kwargs clear enter entry eta None priority 0 queue class celery concurrency eventlet TaskPool args kwargs class Timer schedule None on_error None on_tick Non
422. side of Django for information about using this monitor if you re not using Django To use the Django admin monitor you need to do the following 1 Create the new database tables python manage py syncdb 200 Chapter 11 Change history Celery Documeniation Release 2 5 5 See also 2 Start the django celery snapshot camera python manage py celerycam 3 Open up the django admin to monitor your cluster The admin interface shows tasks worker nodes and even lets you perform some actions like revok ing and rate limiting tasks and shutting down worker nodes There s also a Debian init d script for ce leryev available see Running celeryd as a daemon for more information New command line arguments to celeryev c camera Snapshot camera class to use logfile f Log file loglevel 1 Log level maxrate r Shutter rate limit freq F Shutter frequency The camera argument is the name of a class used to take snapshots with It must support the interface defined by celery events snapshot Polaroid Shutter frequency controls how often the camera thread wakes up while the rate limit controls how often it will actually take a snapshot The rate limit can be an integer snapshots s or a rate limit string which has the same syntax as the task rate limit strings 200 m 10 s I h etc For the Django camera case this rate limit can be used
423. signals worker_process_init Sent inside the pool worker process at init e celeryd Q option Ability to specify list of queues to use disabling other configured queues For example if CELERY_QUEUES defines four queues image video data and default the following command would make celeryd only consume from the image and video queues celeryd Q image video e celeryd New return value for the revoke control command Now returns ok task Sid revoked instead of True e celeryd Can now enable disable events using remote control Example usage gt gt gt from celery task control import broadcast gt gt gt broadcast enable_events gt gt gt broadcast disable _events e Removed top level tests directory Test config now in celery tests config This means running the unit tests doesn t require any special setup celery tests __init__ now con figures the CELERY_CONFIG_MODULE and CELERY_LOADER environment variables so when nosetests imports that the unit test environment is all set up Before you run the tests you need to install the test requirements pip install r contrib requirements test txt Running all tests nosetests Specifying the tests to run nosetests celery tests test_task Producing HTML coverage nosetests with coverage3 The coverage output is then located in celery tests cover index html e celeryd New opti
424. sks and Executing Tasks 1 4 Resources 1 4 Resources 15 Celery Documentation Release 2 5 5 e Getting Help Mailing list IRC e Bug tracker e Wiki e Contributing e License 1 4 1 Getting Help Mailing list For discussions about the usage development and future of celery please join the celery users mailing list IRC Come chat with us on IRC The celery channel is located at the Freenode network 1 4 2 Bug tracker If you have any suggestions bug reports or annoyances please report them to our issue tracker at http github com celery celery issues 1 4 3 Wiki http wiki github com celery celery 1 4 4 Contributing Development of celery happens at Github http github com celery celery You are highly encouraged to participate in the development of celery If you don t like Github for some reason you re welcome to send regular patches Be sure to also read the Contributing to Celery section in the documentation 1 4 5 License This software is licensed under the New BSD License See the LICENSE file in the top distribution directory for the full license text 16 Chapter 1 Getting Started CHAPTER 2 User Guide Release 2 5 Date February 04 2014 2 1 Overview e Tasks e Workers e Monitoring e Routing e Ecosystem Kombu cyme celerymon JO4IOM 4sex401g Asajao Figure 2 1 Figure 1 Worker and broker nodes T
425. smethod AsyncResult task_id Get AsyncResult instance for this kind of task Parameters task_id Task id to get result for class ErrorMail task kwargs Defines how and when task error e mails should be sent Parameters task The task instance that raised the error subject and body are format strings which are passed a context containing the following keys name Name of the task UUID of the task eXC String representation of the exception eargs Positional arguments ekwargs Keyword arguments traceback String representation of the traceback ehostname Worker hostname should_send context exc Returns true or false depending on if a task error mail should be sent for this type of error exception BaseTask MaxRetriesExceededError The tasks max restart limit has been exceeded BaseTask Strategy celery worker strategy default Execution strategy used or the qualified name of one BaseTask abstract None If True the task is an abstract base class BaseTask accept_magic_kwargs False If disabled the worker will not forward magic keyword arguments Deprecated and scheduled for removal in v3 0 BaseTask acks_late False When enabled messages for this task will be acknowledged after the task has been executed and not just before which is the default behavior Please note that this means the task may be executed twice if the worker crashes mid execution which may be acceptable for some
426. spatcher args kwds 12 29 celery events state celery events state j 12 29 celery events state 293 Celery Documentation Release 2 5 5 12 29 1 celery events state This module implements a datastructure used to keep track of the state of a cluster of workers and the tasks it is working on by consuming events For every event consumed the state is updated so the state represents the state of the cluster at the time of the last event Snapshots celery events snapshot can be used to take pictures of this state at regular intervals to e g store that in a database copyright 3 2009 2012 by Ask Solem license BSD see LICENSE for more details class celery events state Element Base class for worker state elements celery events state HEARTBEAT_EXPIRE 150 Hartbeat expiry time in seconds The worker will be considered offline if no heartbeat is received within this time Default is 2 30 minutes class celery events state State callback None max_workers_in_memory 5000 max_tasks_in_memory 10000 Records clusters state alive_workers Returns a list of seemingly alive workers clear ready True clear_tasks ready True event event event_count 0 freeze while fun args kwargs get_or_create_task uuid Get or create task by uuid get_or_create_worker hostname kwargs Get or create worker by hostname itertasks limit None task_count 0 task_event type
427. ss e Using SQLAlchemy e Using the Django Database Using a database as a message queue is not recommended but can be sufficient for very small installations Celery can use the SQLAlchemy and Django ORM e and more In addition to the above there are several other transport implementations to choose from including Using CouchDB Using Beanstalk Using MongoDB and SQS There is a Transport Comparison in the Kombu documentation 1 3 2 Creating a simple task In this tutorial we are creating a simple task that adds two numbers Tasks are defined in normal Python modules By convention we will call our module tasks py and it looks like this file tasks py from celery task import task task def add x y return x y Behind the scenes the task decorator actually creates a class that inherits from Task The best practice is to only create custom task classes when you want to change generic behavior and use the decorator to define tasks See also The full documentation on how to create tasks and task classes is in the Tasks part of the user guide 1 3 3 Configuration Celery is configured by using a configuration module By default this module is called celeryconfig py The configuration module must either be in the current directory or on the Python path so that it can be imported You can also set a custom name for the configuration module by using the CELERY_CONF IG_MODULE environment variable Let s cr
428. ss or the name of the backend class to use Default is the value of the CELERY_R ESULT_BACK amgqp AMQP object or class name events Events object or class name log Log object or class name control Control object or class name END setting set_as_current Make this the global current app 245 Celery Documentation Release 2 5 5 main Name of the __main__ module Required for standalone scripts If set this will be used instead of __main__ when automatically generating task names amqp Sending receiving messages See AMOP backend Storing retrieving task state See BaseBackend loader Current loader conf Current configuration dict and attribute access control Controlling worker nodes See Control log Logging utilities See Logging config_from_object obj silent False Read configuration from object where object is either a object or the name of a module to import gt gt gt celery config_from_object myapp celeryconfig gt gt gt from myapp import celeryconfig gt gt gt celery config_from_object celeryconfig config_from_envvar variable_name silent False Read configuration from environment variable The value of the environment variable must be the name of a module to import gt gt gt os environ CELERY_CONFIG_MODULE myapp celeryconfig gt gt gt celery config_from_envvar CELERY_CONFIG_MODULE config_from_cmdl
429. sses TaskPool celery concurrency proc ses TaskPool Does not try to look up non string names gt gt gt from celery concurrency processes import TaskPool gt gt gt get_cls_by_name TaskPool is TaskPool True celery utils import_from_cwd module imp None package None Import module but make sure it finds modules located in the current directory Modules located in the current directory has precedence over modules located in sys path celery utils instantiate name args kwargs Instantiate class by name See get_cls_by_name celery utils is_iterable obj celery utils isatty fh celery utils lpmerge L R Left precedent dictionary merge Keeps values from J if the value in r is None celery utils mattrgetter attrs Like operator itemgetter but returns None on missing attributes instead of raising AttributeError celery utils maybe_reraise Reraise if an exception is currently being handled or return otherwise celery utils module_file module 378 Chapter 13 Internals Celery Documeniation Release 2 5 5 class celery utils mpromise fun args kwargs Memoized promise The function is only evaluated once every subsequent access will return the same value evaluated Set to to True after the promise has been evaluated evaluate evaluated False celery utils noop args kwargs No operation Takes any arguments keyword arguments and does nothing celery
430. stallation To do this use python to find the location of this module python gt gt gt import celery platform gt gt gt celery platform lt module celery platform from opt devel celery celery platform pyc gt Here the compiled module is in opt devel celery celery to remove the offending files do rm f opt devel celery celery platform py 11 30 2 News e Added support for expiration of AMQP results requires RabbitMQ 2 1 0 The new configuration option CELERY_AMOQP_TASK_RESULT_EXPIRES sets the expiry time in seconds can be int or float CE CE H ERY_AMQP_TASK_RESULT_EXPIRES 30 60 1ERY_AMOP_TASK_RESULT_EXPIRES 0 80 H e celeryev Event Snapshots If enabled celeryd sends messages about what the worker is doing These messages are called events The events are used by real time monitors to show what the cluster is doing but they are not very useful for monitoring over a longer period of time Snapshots lets you take pictures of the clusters state at regular intervals This can then be stored in a database to generate statistics with or even monitoring over longer time periods django celery now comes with a Celery monitor for the Django Admin interface To use this you need to run the django celery snapshot camera which stores snapshots to the database at configurable intervals See Using out
431. stead For example if you have from celery task schedules import crontab You should replace that with from celery schedules import crontab The module needs to be renamed because it must be possible to import schedules without importing the celery task module e The following functions have been deprecated and is scheduled for removal in version 2 3 celery execute apply_async Use task apply_async instead celery execute apply CG Jse task apply instead celery execute delay_task Use registry tasks name delay instead e Importing TaskSet from celery task base is now deprecated You should use gt gt gt from celery task import TaskSet instead 11 25 2 2 0 193 Celery Documeniation Release 2 5 5 e New remote control commands active_queues Returns the queue declarations a worker is currently consuming from e Added the ability to retry publishing the task message in the event of connection loss or failure This is disabled by default but can be enabled using the CELERY_TASK_PUBLISH_RETRY setting and tweaked by the CELERY_TASK_PUBLISH_RETRY_POLICY setting In addition retry and retry_policy keyword arguments have been added to Task apply_async Note Using the retry argument to apply_async requires you to handle the publisher connection manually e Periodic Task classes periodic_task PeriodicTask will not be deprecated as previously in
432. stop retrying BaseTask name None Name of the task BaseTask on_failure exc task_id args kwargs einfo Error handler This is run by the worker when the task fails Parameters e exc The exception raised by the task e task_id Unique id of the failed task e args Original arguments for the task that failed e kwargs Original keyword arguments for the task that failed e einfo ExceptionInfo instance containing the traceback The return value of this handler is ignored BaseTask on_retry exc task_id args kwargs einfo Retry handler This is run by the worker when the task is to be retried Parameters e exc The exception sent to retry e task_id Unique id of the retried task e args Original arguments for the retried task e kwargs Original keyword arguments for the retried task e einfo ExceptionInfo instance containing the traceback The return value of this handler is ignored BaseTask on_success retval task_id args kwargs Success handler Run by the worker if the task executes successfully Parameters e retval The return value of the task e task_id Unique id of the executed task e args Original arguments for the executed task e kwargs Original keyword arguments for the executed task The return value of this handler is ignored BaseTask priority None Default message priority A number between 0 to 9 where 0 is the highest Note
433. store backend as it does not use polling Raises celery exceptions TimeoutError if timeout is not None and the result does not arrive within timeout seconds If the remote call raised an exception then that exception will be re raised celery result BaseAsyncResult alias of AsyncResult class celery result EagerResult task_id ret_value state traceback None Result that we know has already been executed forget get timeout None propagate True kwargs ready result The tasks return value revoke state The tasks state status The tasks state traceback The traceback if the task failed wait timeout None propagate True kwargs class celery result ResultSet results app None kwargs Working with more than one result Parameters results List of result instances add result Add AsyncResult as a new member of the set 270 Chapter 12 API Reference Celery Documeniation Release 2 5 5 Does nothing if the result is already a member clear Remove all results from this set completed_count Task completion count Returns the number of tasks completed discard result Remove result from the set if it is a member If it is not a member do nothing failed Did any of the tasks fail Returns True if any of the tasks failed i e raised an exception forget Forget about and possible remove the result of all the tasks iter_native timeout None
434. stuck with Python 2 4 Complain to your package maintainers sysadmins and bosses tell them it s time to move on Apart from wanting to take advantage of with statements coroutines conditional expressions and enhanced try blocks the code base now contains so many 2 4 related hacks and workarounds it s no longer just a compromise but a sacrifice If it really isn t your choice and you don t have the option to upgrade to a newer version of Python you can just continue to use Celery 2 2 Important fixes can be backported for as long as there is interest e celeryd Now supports Autoscaling of child worker processes The autoscale option can be used to configure the minimum and maximum number of child worker processes autoscale AUTOSCALE Enable autoscaling by providing max_concurrency min_concurrency Example autoscale 10 3 always keep 3 processes but grow to 10 if necessary e Remote Debugging of Tasks celery contrib rdb is an extended version of pdb that enables remote debugging of processes that does not have terminal access Example usage from celery contrib import rdb from celery task import task task def add x y result x y rdb set_trace lt set breakpoint return result func celery contrib rdb set_trace sets a breakpoint at the current location and creates a socket you can telnet into to remotely debug your task The debugger may be started by multiple processes
435. sumer ttype kombu messaging Consumer Warning If you don t specify a connection one will automatically be established for you in that case you need to close this connection after use gt gt gt consumer get_consumer gt gt gt gt gt gt consumer close gt gt gt consumer connection close classmethod BaseTask get_logger loglevel None logfile None propagate False kwargs Get task aware logger object classmethod BaseTask get_publisher connection None exchange None con nect_timeout None exchange_type None options Get a celery task message publisher type TaskPublisher Warning If you don t specify a connection one will automatically be established for you in that case you need to close this connection after use gt gt gt publisher get_publisher gt gt gt i gt gt gt publisher connection close or used as a context gt gt gt with get_publisher as publisher BaseTask ignore_result False If enabled the worker will not store task state and return values for this task Defaults to the CELERY_IGNORE_RESULT setting BaseTask immediate False Request immediate delivery 252 Chapter 12 API Reference Celery Documeniation Release 2 5 5 BaseTask mandatory False Mandatory message routing BaseTask max_retries 3 Maximum number of retries before giving up If set to None it will never
436. t classmethod BaseTask delay args kwargs Star argument version of apply_async Does not support the extra options enabled by apply_async Parameters e args positional arguments passed on to the task e kwargs keyword arguments passed on to the task returns celery result AsyncResult BaseTask delivery_mode None Override the apps default delivery mode for this task Default is persistent but you can change this to transient which means messages will be lost if the broker is restarted Consult your broker manual for any additional delivery modes BaseTask error_whitelist List of exception types to send error emails for classmethod BaseTask establish_connection connect_timeout None Establish a connection to the message broker BaseTask exchange None Overrides the apps default exchange for this task BaseTask exchange_type None Overrides the apps default exchange type for this task 12 2 celery app task 251 Celery Documentation Release 2 5 5 BaseTask execute request pool loglevel logfile kwargs The method the worker calls to execute the task Parameters e request A Request e pool A task pool e loglevel Current loglevel logfile Name of the currently used logfile consumer The Consumer BaseTask expires None Default task expiry time classmethod BaseTask get_consumer connection None connect_timeout None Get message con
437. t be called as soon as the connection is re established You need to close this after use close Close the event dispatcher copy_buffer other disable 292 Chapter 12 API Reference Celery Documeniation Release 2 5 5 enable flush send type fields Send event Parameters e type Kind of event e fields Event arguments class celery events EventReceiver connection handlers None routing_key node_id None app None queue_prefix celeryev Capture events Parameters e connection Connection to the broker handlers Event handlers handlers is a dict of event types and their handlers the special handler captures all events that doesn t have a handler capture limit None timeout None wakeup True Open up a consumer capturing events This has to run in the main process and it will never stop unless forced via KeyboardInterrupt or SystemExit consumer args kwds Create event consumer drain_events kwargs handlers itercapture imit None timeout None wakeup True process type event Process the received event by dispatching it to the appropriate handler wakeup_workers channel None class celery events Events app None Dispatcher connection None hostname None enabled True channel None buffer_while_offline True Receiver connection handlers None routing_key node_id None State default_di
438. t_timeout 3 2 3 6 Routing options Celery uses the AMQP routing mechanisms to route tasks to different workers Messages tasks are sent to exchanges a queue binds to an exchange with a routing key Let s look at an example Let s pretend we have an application with lot of different tasks some process video others process images and some gather collective intelligence about its users Some of these tasks are more important so we want to make sure the high priority tasks get sent to dedicated nodes For the sake of this example we have a single exchange called tasks There are different types of exchanges each type interpreting the routing key in different ways implementing different messaging scenarios The most common types used with Celery are direct and topic e direct 40 Chapter 2 User Guide Celery Documentation Release 2 5 5 Matches the routing key exactly e topic In the topic exchange the routing key is made up of words separated by dots Words can be matched by the wild cards and where matches one exact word and matches one or many words For example stock matches the routing keys usd stock and euro stock db but not stock nasdaq We create three queues video image and lowpri that binds to the tasks exchange For the queues we use the following binding keys video video image image lowpri misc Now we can send our tasks to different worker machines by making the work
439. tarted Proxy objects now redirects __ doc___ and___ name___ so he lp obj works Internal timer timer2 now logs exceptions instead of swallowing them Issue 626 celeryctl shell can now be started with vent let or gevent options to apply their monkey patches 11 5 2 5 0 release date 2012 02 24 04 00 P M GMT by Ask Solem See What s new in Celery 2 5 Since the changelog has gained considerable size we decided to do things differently this time by having separate what s new documents for major version changes Bugfix releases will still be found in the changelog 11 6 2 4 5 release date 2011 12 02 05 00 PM GMT by Ask Solem e Periodic task interval schedules were accidentally rounded down resulting in some periodic tasks being executed early e Logging of humanized times in the celerybeat log is now more detailed e New Brokers section in the Getting Started part of the Documentation This replaces the old Using Celery with Redis Database as the messaging queue tutorial and adds documentation for MongoDB Beanstalk and CouchDB 11 4 2 5 1 173 Celery Documeniation Release 2 5 5 11 7 2 4 4 release date 2011 11 25 16 00 P M GMT by Ask Solem 11 7 1 Security Fixes e Security CELERYSA 0001 Daemons would set effective id s rather than real id s when the uid gid arguments to celeryd multi celeryd_detach celerybeat and celeryev were used This means privileges weren t pro
440. tegration has been moved to a separate package django celery e To upgrade you need to install the django celery module and change INSTALLED_APPS celery to INSTALLED_APPS djcelery e If you use mod_wsgi you need to add the following line to your wsgi file 11 34 2 0 0 211 Celery Documeniation Release 2 5 5 import os os environ CELERY_LOADER django e The following modules has been moved to django celery Module name Replace with celery models djcelery models celery managers djcelery managers celery views djcelery views celery urls djcelery urls celery management djcelery management celery loaders djangoapp djcelery loaders celery backends database djcelery backends database celery backends cache djcelery backends cache Importing djcelery will automatically setup Celery to use Django loader loader It does this by setting the CELERY_LOADER environment variable to django it won t change it if a loader is already set When the Django loader is used the database and cache result backend aliases will point to the djcelery backends instead of the built in backends and configuration will be read from the Django settings 11 34 3 Upgrading for others Database result backend The database result backend is now using SQLAIchemy instead of the Django ORM see Supported Databases for a table of supported databases The DATABASE_ settings h
441. tform 390 Chapter 13 Internals Celery Documeniation Release 2 5 5 update _d_ None sigmap Set signal handlers from a mapping celery platforms create_pidlock pidfile Create and verify pid file If the pid file already exists the program exits with an error message however if the process it refers to is not running anymore the pid file is deleted and the program continues The caller is responsible for releasing the lock before the program exits Returns PIDFile Example import atexit pidlock create_pidlock var run app pid acquire atexit register pidlock release celery platforms detached logfile None pidfile None uid None gid None umask 0 workdir None fake False opts Detach the current process in the background daemonize Parameters e logfile Optional log file The ability to write to this file will be verified before the process is detached e pidfile Optional pid file The pid file will not be created as this is the responsibility of the child But the process will exit if the pid lock exists and the pid written is still running e uid Optional user id or user name to change effective privileges to e gid Optional group id or group name to change effective privileges to e umask Optional umask that will be effective in the child process e workdir Optional new working directory e fake Don t actually detach intented for debugging purposes e
442. that is to use REST tasks instead of your tasks being functions they re URLs With this information you can even create simple web servers that enable preloading of code See User Guide Remote Tasks 9 3 Troubleshooting 9 3 1 MySQL is throwing deadlock errors what can do Answer MySQL has default isolation level set to REPEATABLE READ if you don t really need that set it to READ COMMITTED You can do that by adding the following to your my cnf mysqld transaction isolation READ COMMITTED For more information about InnoDB s transaction model see MySQL The InnoDB Transaction Model and Locking in the MySQL user manual Thanks to Honza Kral and Anton Tsigularov for this solution 9 3 2 celeryd is not doing anything just hanging Answer See MySQL is throwing deadlock errors what can I do or Why is Task delay apply just hanging 9 3 3 Task results aren t reliably returning Answer If you re using the database backend for results and in particular using MySQL see MySQL is throwing deadlock errors what can I do 9 3 4 Why is Task delay apply celeryd just hanging Answer There is a bug in some AMQP clients that will make it hang if it s not able to authenticate the current user the password doesn t match or the user does not have access to the virtual host specified Be sure to check your broker logs for RabbitMQ that is var log rabbitmq rabbit 1log on most systems it usually contains
443. the default queue named celery for historical reasons Now you can start server z to only process the feeds queue like this z celeryd Q feeds You can specify as many queues as you want so you can make this server process the default queue as well z celeryd Q feeds celery Changing the name of the default queue You can change the name of the default queue by using the following configuration CELERY_QUEUES default exchange default binding_key default CELERY_DEFAULT_QUEUE default 2 8 Routing Tasks 59 Celery Documentation Release 2 5 5 How the queues are defined The point with this feature is to hide the complex AMQP protocol for users with only basic needs However you may still be interested in how these queues are declared A queue named video will be created with the following settings exchange video exchange_type direct routing_key video The non AMQP backends like ghettog does not support exchanges so they require the exchange to have the same name as the queue Using this design ensures it will work for them as well Manual routing Say you have two servers x and y that handles regular tasks and one server z that only handles feed related tasks you can use this configuration CELERY_DEFAULT_QUEUE default CELERY_QUEUES default binding_key task
444. the task as being retried Note that this means the task will be marked as failed if the task raises an exception or successful if it returns Raises celery exceptions RetryTaskError To tell the worker that the task has been re sent for retry This always happens unless the throw keyword argument has been explicitly set to False and is considered normal operation Example gt gt gt task gt gt gt def tweet auth message twitter Twitter oauth auth try twitter post_status_update message except twitter FailWhale exc return tweet retry countdown 60 5 exc exc Although the task will never return above as retry raises an exception to notify the worker we use return in front of the retry to convey that the rest of the block will not be executed BaseTask run args kwargs The body of the task executed by workers classmethod BaseTask subtask args kwargs Returns subtask object for this task wrapping arguments and execution options for a single task invo cation BaseTask update_state task_id None state None meta None Update task state Parameters e task_id Id of the task to update e state New state str e meta State metadata dict class celery task base PeriodicTask A periodic task is a task that behaves like a cron job Results of periodic tasks are not stored by default 264 Chapter 12 API Reference Celery Documeniation Release 2 5 5 run_every REQUIRED Defines
445. timer_tick delay pool_cls None pool_putlocks None prefetch_multiplier None process_task request Process task by sending it to the pool of workers reload modules None reload False reloader None schedule_filename None scheduler_cls None send_events None start Starts the workers main loop state state_db None stop in_sighandler False Graceful shutdown of the worker server task_soft_time_limit None task_time_limit None terminate in_sighandler False Not so graceful shutdown of the worker server 13 6 3 celery worker consumer e celery worker consumer j celery worker consumer This module contains the component responsible for consuming messages from the broker processing the messages and keeping the broker connections up and running copyright 13 6 Internal Module Reference 327 Celery Documentation Release 2 5 5 class 3 2009 2012 by Ask Solem license BSD see LICENSE for more details start is an infinite loop which only iterates again if the connection is lost For each iteration at start or if the connection is lost it calls reset_connection and starts the consumer by calling consume_messages reset_connection clears the internal queues establishes a new connection to the broker sets up the task consumer QoS and the broadcast remote control command consumer Also if events are enabled it configures the event dispatcher and starts
446. to control how often the snapshots are written to the database and the frequency used to control how often the thread wakes up to check if there s anything new The rate limit is off by default which means it will take a snapshot for every frequency sec onds Django Admin Monitor and Snapshots e broadcast Added callback argument this can be used to process replies immediately as they arrive e celeryctl New command line utility to manage and inspect worker nodes apply tasks and inspect the results of tasks See also The celeryctl Management Utility section in the User Guide Some examples celeryctl apply tasks add a 2 2 countdown 10 celeryctl inspect active celeryctl inspect registered_tasks celeryctl inspect scheduled celeryctl inspect help celeryctl apply help NONONO wn e Added the ability to set an expiry date and time for tasks Example 11 30 2 1 0 201 Celery Documeniation Release 2 5 5 gt gt gt k expil 21 ninu from now gt gt gt task apply_async args kwargs expires 60 gt gt gt ls upport late gt gt gt task apply_async args kwargs xpires datetime now timedelta days 1 When a worker receives a task that has been expired it will be marked as revoked celery exceptions TaskRevokedError e Changed the way logging is configured We now configure the root logger instead of only configuring our custom logger In addition we don t
447. too frequent or you want to have higher precision then you can change this using the frequency argument This is a float describing how often in seconds it should wake up to check if there are any new events 2 9 Monitoring and Management Guide 69 Celery Documeniation Release 2 5 5 S python manage py celerycam frequency 3 0 The camera also supports rate limiting using the maxrate argument While the frequency controls how often the camera thread wakes up the rate limit controls how often it will actually take a snapshot The rate limits can be specified in seconds minutes or hours by appending s m or h to the value Example maxrate 100 m means hundred writes a minute The rate limit is off by default which means it will take a snapshot for every frequency seconds The events also expire after some time so the database doesn t fill up Successful tasks are deleted after 1 day failed tasks after 3 days and tasks in other states after 5 days Using outside of Django django celery also installs the djcelerymon program This can be used by non Django users and runs both a web server and a snapshot camera in the same process Installing Using pip pip install U django celery or using easy_install easy_install U django celery Running djcelerymon reads configuration from your Celery configuration module and sets up the Django environment using the same settings djcelerymon
448. ts there e Security Isn t using pickle a security concern Can messages be encrypted Is it safe to run celeryd as root e Brokers Why is RabbitMQ crashing Can I use Celery with Active MQ STOMP What features are not supported when not using an AMQP broker e Tasks How can I reuse the same connection when applying tasks Sudo ina subprocess returns None Why do workers delete tasks from the queue if they are unable to process them Can I execute a task by name How can I get the task id of the current task Can I specify a custom task_id Can I use decorators with tasks Can I use natural task ids How can I run a task once another task has finished Can I cancel the execution of a task Why aren t my remote control commands received by all workers Can I send some tasks to only some servers Can I change the interval of a periodic task at runtime Does celery support task priorities Should I use retry or acks_late Can I schedule tasks to execute at a specific time How do I shut down celeryd safely How do I run celeryd in the background on platform e Django What purpose does the database tables created by django celery have e Windows celeryd keeps spawning processes at startup The B beat option to celeryd doesn t work django celery can t find settings 150 Chapter 9 Frequently Asked Questions C
449. tting or the I include option This is an experimental feature intended for use in development only using auto reload in production is discouraged as the behavior of reloading a module in Python is undefined and may cause hard to diagnose bugs and crashes Celery uses the same approach as the auto reloader found in e g the Django runserver command When auto reload is enabled the worker starts an additional thread that watches for changes in the file system New modules are imported and already imported modules are reloaded whenever a change is detected and if the processes pool is used the child processes will finish the work they are doing and exit so that they can be replaced by fresh processes effectively reloading the code File system notification backends are pluggable and Celery comes with three implementations e inotify Linux Used if the pyinotify library is installed If you are running on Linux this is the recommended implementation to install the pyinotify library you have to run the following command pip install pyinotify e kqueue OS X BSD e stat The fallback implementation simply polls the files using st at and is very expensive You can force an implementation by setting the CELERYD_FSNOTIFY environment variable env CELERYD_FSNOTIFY stat celeryd l info autoreload Contributed by Mher Movsisyan 10 4 4 New CELERY_ANNOTATIONS setting This new setting enables th
450. ttings e tyrant Use Tokyo Tyrant to store the results See Tokyo Tyrant backend settings e amqp Send results back as AMQP messages See AMQP backend settings e cassandra Use Cassandra to store the results See Cassandra backend settings 3 2 Configuration Directives 89 Celery Documentation Release 2 5 5 CELERY_RESULT_SERIALIZER Result serialization format Default is pickle See Serializers for information about supported serialization formats 3 2 6 Database backend settings CELERY_RESULT_DBURI Please see Supported Databases for a table of supported databases To use this backend you need to configure it with an Connection String some examples include e filename CELERY_RESULT_DBURI sqlite celerydb sqlite SOL1 _RESULT_DBURI mysql scott tiger localhost foo CELERY_RESULT_DBURI postgresql scott tiger localhost mydatabase CELERY_RESULT_DBURI oracle scott tiger 127 0 0 1 1521 sidname See Connection String for more information about connection strings CELERY_RESULT_ENGINE_OPTIONS To specify additional SQLAIchemy database engine options you can use the CELERY_RESULT_ENGINE_OPTIONS setting y f r COTAITchemy LG ing Erom oGVLALcnemy hi FFL Tl x 3 CELERY_RESULT_ENGINE_OPTIONS echo True echo enables verbose Short lived sessions are disabled by default If enabl
451. u do In this tutorial we will send the individual clicks as messages using kombu and then process them later with a Celery periodic task Celery and Kombu are excellent in tandem and while this might not be the perfect example you ll at least see one example how of they can be used to solve a task 8 3 2 The model The model is simple Click has the URL as primary key and a number of clicks for that URL Its manager ClickMan ager implements the increment_clicks method which takes a URL and by how much to increment its count by clickmuncher models py from django db import models from django utils translation import ugettext_lazy as _ class ClickManager models Manager def increment_clicks for_url increment_by 1 Tncrement the click count for an URL gt gt gt Click objects increment_clicks http google com 10 nun click created get_or_create url for_url defaults click_count increment_by if not created click click_count increment_by click save return click click_count 8 3 Tutorial Creating a click counter using Kombu and celery 145 Celery Documeniation Release 2 5 5 class Click models Model url models URLField _ u URL verify_exists A click_count models PositiveIntegerField _ u click_count default 0 objects ClickManager class Meta verbose_name _ u URL clicks verbose_name_plural _ u URL clicks 8 3 3 Using Kombu to send clicks
452. uage and a PHP client The recommended message broker is RabbitMQ but support for Redis MongoDB Beanstalk Amazon SQS CouchDB and databases using SQLAIchemy or the Django ORM is also available Celery is easy to integrate with web frameworks some of which even have integration packages Django django celery Pyramid pyramid_celery Pylons celery pylons Flask flask celery web2py web2py celery 1 1 2 Overview This is a high level overview of the architecture The broker delivers tasks to the worker nodes A worker node is a networked machine running celeryd This can be one or more machines depending on the workload The result of the task can be stored for later retrieval called its tombstone 1 1 3 Example You probably want to see some code by now so here s an example task adding two numbers from celery task import task task def add x y return x y You can execute the task in the background or wait for it to finish gt gt gt result add delay 4 4 gt gt gt result wait wait for and return the result Simple 4 Chapter 1 Getting Started Celery Documeniation Release 2 5 5 1 1 4 Features Mes Supported brokers include RabbitMQ Redis Beanstalk MongoDB CouchDB and saging popular SQL databases Fault Excellent configurable error recovery when using RabbitMQ ensures your tasks are never tolerant lost Dis Runs on one or more machines Supp
453. ule sync class celery beat ScheduleEntry name None task None last_run_at None to tal_run_count None schedule None args kwargs options relative False An entry in the scheduler Parameters e name see name e schedule see schedule e args see args e kwargs see kwargs e options see options e last_run_at see last_run_at e total_run_count see total_run_count e relative Is the time relative to when the server starts args None Positional arguments to apply is_due See celery task base PeriodicTask is_due kwargs None Keyword arguments to apply last_run_at None The time and date of when this task was last scheduled name None The task name next last_run_at None Returns a new instance of the same class but with its date and count fields updated options None Task execution options schedule None The schedule run_every crontab total_run_count 0 Total number of times this task has been scheduled update other Update values from another entry Does only update editable fields task schedule args kwargs options class celery beat Scheduler schedule None logger None max_interval None app None Pub lisher None lazy False kwargs Scheduler for periodic tasks Parameters e schedule see schedule e logger see Logger e max_interval see max_interval Entry alias of ScheduleEntry add kwargs a
454. unksize None Equivalent of map builtin askPool Pool map_asyne func iterable chunksize None callback None Asynchronous equivalent of map builtin askPool Pool restart askPool Pool shrink n askPool Pool terminate TaskPool grow n 13 6 Internal Module Reference 341 Celery Documentation Release 2 5 5 TaskPool num_processes TaskPool on_start Run the task pool Will pre fork all workers so they re ready to accept tasks askPool on_stop Gracefully stop the pool askPool on_terminate Force terminate the pool askPool requires_mediator True askPool restart askPool shrink n askPool terminate_job pid signal None celery concurrency processes WORKER_SIGIGNORE frozenset SIGINT List of signals to ignore when a child process starts celery concurrency processes WORKER_SIGRESET frozenset SIGHUP SIGTERM SIGTTOU SIGTTIN lt List of signals to reset when a child process starts celery concurrency processes process_initializer app hostname Initializes the process so it can be used to process tasks 13 6 15 celery concurrency processes pool class celery concurrency processes pool ApplyResult cache callback ac cept_callback None time out_callback None er ror_callback None soft_timeout None timeout None lost_worker_timeout 10 0 accepted get timeout None ready
455. up the heartbeat thread Finally it can consume messages consume_messages is simply an infinite loop waiting for events on the AMQP channels Both the task consumer and the broadcast consumer uses the same callback receive_message So for each message received the receive_message method is called this checks the payload of the message for either a task key or a control key If the message is a task it verifies the validity of the message converts it to a celery worker job Request and sends it to on_task If the message is a control command the message is passed to on_cont rol which in turn dispatches the control command using the control dispatcher It also tries to handle malformed or invalid messages properly so the worker doesn t choke on them and die Any invalid messages are acknowledged immediately and logged so the message is not resent again and again If the task has an ETA countdown the task is moved to the eta_schedule so the timer2 Timer can schedule it at its deadline Tasks without an eta are moved immediately to the ready_queue so they can be picked up by the Mediator to be sent to the pool When a task with an ETA is received the QoS prefetch count is also incremented so another message can be reserved When the ETA is met the prefetch count is decremented again though this cannot happen immediately because amgqplib doesn t support doing broker requests across threads Instead the current pre
456. urn the original datetime celery utils timeutils humanize_seconds secs prefix Show seconds in human form e g 60 is 1 minute 7200 is 2 hours celery utils timeutils maybe_iso8601 dt Either datetime str gt datetime or None gt None celery utils timeutils maybe_timedelta delta Coerces integer to timedelta if delta is an integer celery utils timeutils rate rate Parses rate strings such as J00 m or 2 h and converts them to seconds celery utils timeutils remaining start ends_in now None relative False Calculate the remaining time for a start date and a timedelta e g how many seconds left for 30 seconds after start Parameters e start Start datetime e ends_in The end delta as at imedelta 13 6 Internal Module Reference 381 Celery Documentation Release 2 5 5 e relative If enabled the end time will be calculated using delta_resolution i e rounded to the resolution of ends_in now datetime utcnow Function returning the current time and date defaults to celery utils timeutils timedelta_seconds delta Convert datetime timedelta to seconds Doesn t account for negative values celery utils timeutils weekday name Return the position of a weekday 0 7 where 0 is Sunday Example gt gt gt weekday sunday weekday sun weekday mon C l 13 6 48 celery utils encoding celery utils en
457. urses Monitor New in version 2 0 celeryev is a simple curses monitor displaying task and worker history You can inspect the result and traceback of tasks and it also supports some management commands like rate limiting and shutting down workers o_o celeryev 1 1 1 UUID bed79a28 3819 4904 975 Workers online casper local SebSa7aae2d5 2599b117 3c10 45383 8544 2e63b284c96F 7a 7fccl 7a13 4878 82a6 738673e4c3d9 75486d0d aae4 4129 bc55 febaa2abed3 e47e2069 a2bf 4af3 a93d c3ef96Ffdl2c 3a7a6759 7fa8 48ec 9F89 b222acd3b49F 1 feclb6 6996 41 f9 a337 989adec5183d fda219d3 c24b 492c b948 9F 9b1945e8d 627428a6 a9ed 4c3b ad64 a869b582e068 872052d0 71b6 4287 a24d d6 fdaGe8ebc c8d a21e aac2 4f3a 90d6 fee3b94caaca 1c9d67d8 b8f 4fd 8d30 e72694526dF3 6b179F86 4be5 4b e a81b e25525c3a02a c 2ffdid 36a8 4 c4 a5a1 SaedfcbaSeeb tasks sleeptask casper local 3795b272 b5e4 429e 84e3 583d8e02261b tasks sleeptask casper local 641 ee9b Gea7 4fF8 b40d 4ca023038fel tasks sleeptask casper local 6d1 4daf2 5025 48e38 b445 ca4b9fcc9369 tasks sleeptask casper local Info events 43 tasks 2 workers 1 1 Keys j up k down i info t traceback r result c revoke c quit TASK WORKER 63aa2f21 433e 4cae 8882 9FFFFc2cO9d6 tasks sleeptask casper local f cca35b5 8b52 49a4 a79e 31 a 747a tasks sleeptask casper local tasks sleeptask casper loca tasks sleeptask casper local tasks sleeptask casper local tasks sleeptask casper local tasks sleeptask casper
458. utils padlist container size default None Pad list with default elements Examples gt gt gt first last city padlist George Costanza NYC 3 George Costanza NYC gt gt gt first last city padlist George Costanza 3 George Costanza ne gt gt gt first last city planet padlist George Costanza NYC 4 default Earth George Costanza NYC Earth celery utils pluralize n text suffix s celery utils qualname obj celery utils reload_from_cewd module reloader None celery utils textindent t indent 0 Indent text celery utils truncate_text text maxlen 128 suffix Truncates text to a maximum number of characters celery utils unigq it celery utils warn_deprecated description None deprecation None removal None alterna tive None 13 6 45 celery utils functional celery utils functional Utilities for functions copyright 3 2009 2012 by Ask Solem license BSD see LICENSE for more details e celery utils functional j 13 6 Internal Module Reference 379 Celery Documentation Release 2 5 5 celery utils functional maybe_list l celery utils functional memoize maxsize None Cache lt class cel ery datastructures LRUCache at 0x1cae8 amp 70 gt 13 6 46 celery utils term e celery utils term j celery utils term Terminals and colors copyright 3 2009 20
459. value of the task e task_id Unique id of the executed task e args Original arguments for the executed task e kwargs Original keyword arguments for the executed task The return value of this handler is ignored on_retry 2 2 10 How it works Here comes the technical details this part isn t something you need to know but you may be interested All defined tasks are listed in a registry The registry contains a list of task names and their task classes You can investigate this registry yourself gt gt gt from celery import registry gt gt gt from celery import task gt gt gt registry tasks celery 2 2 Tasks 31 Celery Documeniation Release 2 5 5 y execute e_ remote regular gt ery map_async regular gt lt Task celery ping regular gt This is the list of tasks built in to celery Note that we had to import celery task first for these to show up This is because the tasks will only be registered when the module they are defined in is imported The default loader imports any modules listed in the CELERY_IMPORTS setting The entity responsible for registering your task in the registry is a meta class TaskType This is the default meta class for BaseTask If you want to register your task manually you can mark the task as abstract class MyTask Task abstract This way the task won t be registered but any task inheriting from it will be
460. vents on disk may be very expensive A sequence of events describes the cluster state in that time period by taking periodic snapshots of this state we can keep all history but still only periodically write it to disk To take snapshots you need a Camera class with this you can define what should happen every time the state is captured You can write it to a database send it by email or something else entirely celeryev is then used to take snapshots with the camera for example if you want to capture state every 2 seconds using the camera myapp Camera you run celeryev with the following arguments S celeryev c myapp Camera frequency 2 0 Custom Camera Here is an example camera dumping the snapshot to screen 2 9 Monitoring and Management Guide 73 Celery Documeniation Release 2 5 5 from pprint import pformat from celery events snapshot import Polaroid class DumpCam Polaroid def on_shutter self state if not state event_count return print Workers s pformat state workers indent 4 print Tasks ss pformat state tasks indent 4 print Total s events s tasks state event_count state task_count See the API reference for celery events state to read more about state objects Now you can use this cam with celeryev by specifying it with the c option celeryev c myapp DumpCam frequency 2 0 Or you can use it programmatically like this from celery events im
461. very_mode and the CELERY_DEFAULT_DELIVERY_MODE setting These can be used to mark messages non persistent i e so they are lost if the broker is restarted e Now have our own ImproperlyConfigured exception instead of using the Django one e Improvements to the Debian init scripts Shows an error if the program is not executable Does not modify CELERYD when using django with virtualenv 11 41 1 0 0 release date 2010 02 10 04 00 P M CET 11 41 1 Backward incompatible changes e Celery does not support detaching anymore so you have to use the tools available on your platform or something like Supervisord to make celeryd celerybeat celerymon into background processes We ve had too many problems with celeryd daemonizing itself so it was decided it has to be removed Example startup scripts has been added to contrib Debian Ubuntu start stop daemon contrib debian init d celeryd contrib debian init d celerybeat Mac OS X launchd contrib mac org celeryq celeryd plist _contrib mac org celeryq celerybeat plist con trib mac org celeryq celerymon plist Supervisord http supervisord org contrib supervisord supervisord conf In addition to detach the following program arguments has been removed uid gid workdir chroot pidfile umask All good daemonization tools should support equivalent functionality so don t worry Also the following configuration keys has been removed CE
462. when selecting what classes to include but often it s better to add one too many predicting what users need to override is hard this has saved us from many a monkey patch Example class Worker Consumer Consumer def init s connection consumer_cls N ys Consumer consumer_cls or Consumer 13 1 Contributors Guide to the Code 313 Celery Documentation Release 2 5 5 def do_work ja with lf Consumer lf connection as consumer connection drain_events 13 1 3 Applications vs single mode In the beginning Celery was developed for Django simply because this enabled us get the project started quickly while also having a large potential user base In Django there is a global settings object so multiple Django projects can t co exist in the same process space this later posed a problem for using Celery with frameworks that doesn t have this limitation Therefore the app concept was introduced When using apps you use celery objects instead of importing things from celery submodules this sadly also means that Celery essentially has two API s Here s an example using Celery in single mode from celery task import task from celery task control import inspect from models import CeleryStats task def write_stats_to_db stats inspect stats timeout 1 for node_name reply in stats CeleryStats objects update_stat node_name stats and here s the same using Celery app o
463. which sets the state of the underlying Task to ABORTED abort Set the state of the task to ABORTED Abortable tasks monitor their state at regular intervals and terminate execution if so Be aware that invoking this method does not guarantee when the task will be aborted or even if the task will be aborted at all is_aborted Returns True if the task is being aborted class celery contrib abortable AbortableTask A celery task that serves as a base class for all Task s that support aborting during execution All subclasses of AbortableTask must call the is_aborted method periodically and act accordingly when the call evaluates to True classmethod AsyncResult task_id Returns the accompanying AbortableAsyncResult instance is_aborted kwargs Checks against the backend whether this Abort ableAsyncResult is ABORTED Always returns False incase the task_id parameter refers to a regular non abortable Task Be aware that invoking this method will cause a hit in the backend for example a database query so find a good balance between calling it regularly for responsiveness but not too often for performance name celery contrib abortable AbortableTask 12 25 celery contrib batches Collect messages and processes them as a list Example A click counter that flushes the buffer every 100 messages and every 10 seconds from celery task import task from celery contrib batches import Batches
464. without passing an explicit app instance This is achieved by having all app dependent objects use default_app if the app instance is missing from celery app import app_or_default class SomeClass J3 def init app app app_or_default app The problem with this approach is that there is a chance that the app instance is lost along the way and everything seems to be working normally Testing app instance leaks is hard The environment variable CELERY_TRACE_APP can be used when this is enabled celery app app_or_default will raise an exception whenever it has to go back to the default app instance App Dependency Tree app celery loaders base BaseLoader celery backends base BaseBackend app TaskSet celery task sets TaskSet app TaskSet app TaskSetResult x celery result TaskSetResult app TaskSetResult e app AsyncResult celery result BaseAsyncResult celery result AsyncResult e celery bin celeryd WorkerCommand celery apps worker Worker x celery worker WorkerController celery worker consumer Consumer celery worker job TaskRequest celery events EventDispatcher celery worker control ControlDispatch celery woker control registry Panel celery pidbox BroadcastPublisher celery pidbox BroadcastConsumer 322 Chapter 13 Internals Celery Documeniation Release 2 5 5 celery worker controllers Mediator celery beat EmbeddedService celery bin celeryev run_cele
465. wledged messages on the specified channel Parameters requeue By default the messages will be redelivered to the original re cipient With requeue set to true the server will attempt to requeue the message potentially then delivering it to an alternative subscriber register_callback callback Register a new callback to be called when a message is received The signature of the callback needs to accept two arguments body message which is the decoded message body and the Message instance a subclass of Message revive channel Revive consumer after connection loss class AMOPBackend Exchange name type channel None kwargs An Exchange declaration Parameters e name See name e type See type e channel See channel e durable See durable e auto_delete See auto_delete e delivery_mode See delivery_mode e arguments See arguments name Name of the exchange Default is no name the default exchange type AMQP defines four default exchange types routing algorithms that covers most of the common messaging use cases An AMQP broker can also define additional exchange types so see your broker manual for more information about available exchange types edirect default Direct match between the routing key in the message and the rout ing criteria used when a queue is bound to this exchange topic Wildcard match between the routing key and the routing pattern specified in the exch
466. works best for you as this varies based on application work load task run times and other factors 2 4 5 Persistent revokes Revoking tasks works by sending a broadcast message to all the workers the workers then keep a list of revoked tasks in memory If you want tasks to remain revoked after worker restart you need to specify a file for these to be stored in either by using the statedb argument to celeryd or the CELERYD_STATE_DB setting See CELERYD_STATE_DB for more information 2 4 6 Time limits New in version 2 0 A single task can potentially run forever if you have lots of tasks waiting for some event that will never happen you will block the worker from processing new tasks indefinitely The best way to defend against this scenario happening is enabling time limits The time limit time limit is the maximum number of seconds a task may run before the process executing it is terminated and replaced by a new process You can also enable a soft time limit soft time limit this raises an exception the task can catch to clean up before the hard time limit kills it 2 4 Workers Guide 43 Celery Documeniation Release 2 5 5 from celery task import task from celery exceptions import SoftTimeLimitExceeded task def mytask try do_work except SoftTimeLimitExceeded clean_up_in_a_hurry Time limits can also be set using the CELERYD_TASK_TIME_LIMIT CELERY
467. y also called binding key The interpretation of the routing key depends on the Exchange type edirect exchange Matches if the routing key property of the message and the rout ing_key attribute are identical efanout exchange Always matches even if the binding does not have a key topic exchange Matches the routing key property of the message by a primitive pattern matching scheme The message routing key then consists of words separated by dots like domain names and two special characters are available star and hash The star matches any word and the hash matches zero or more words For example stock matches the routing keys usd stock and eur stock db but not stock nasdaq channel The channel the Queue is bound to if bound durable Durable queues remain active when a server restarts Non durable queues transient queues are purged if when a server restarts Note that durable queues do not necessarily hold persistent mes sages although it does not make sense to send persistent messages to a transient queue Default is True 13 6 Internal Module Reference 361 Celery Documentation Release 2 5 5 exclusive Exclusive queues may only be consumed from by the current connection Setting the exclusive flag always implies auto delete Default is False auto_delete If set the queue is deleted when all consumers have finished using it Last co
468. y certificate FSCertStore path File system certificate store 13 6 Internal Module Reference 367 Celery Documentation Release 2 5 5 13 6 34 celery security key class celery security key PrivateKey key sign data digest sign string containing data 13 6 35 celery security serialization class celery security serialization SecureSerializer key None cert None cert_store None digest shal serializer json deserialize data deserialize data structure from string serialize data serialize data structure into string celery security serialization b6 4decode s celery security serialization b64encode s celery security serialization register_auth key None cert None store None di gest shal serializer json register security serializer 13 6 36 celery datastructures Custom types and data structures copyright 3 2009 2012 by Ask Solem license BSD see LICENSE for more details e AttributeDict e DictAttribute e ConfigurationView e ExceptionInfo e LimitedSet e LRUCache AttributeDict class celery datastructures AttributeDict Dict subclass with attribute access class celery datastructures AttributeDictMixin Adds attribute access to mappings d key gt d key 368 Chapter 13 Internals Celery Documeniation Release 2 5 5 DictAttribute class celery datastructures DictAttribute obj Dict interface to attributes obj k gt ob
469. y more than one worker e task retried uuid exception traceback hostname timestamp Sent if the task failed but will be retried in the future Worker Events e worker online hostname timestamp sw_ident sw_ver Sw_sys The worker has connected to the broker and is online sw_ident Name of worker software e g celeryd sw_ver Software version e g 2 2 0 sw_sys Operating System e g Linux Windows Darwin e worker heartbeat hostname timestamp sw_ident sw_ver sw_sys Sent every minute if the worker has not sent a heartbeat in 2 minutes it is considered to be offline e worker offline hostname timestamp sw_ident sw_ver sSw_sys The worker has disconnected from the broker 2 10 Security e Introduction e Areas of Concern Broker Client Worker e Serializers e Message Signing e Intrusion Detection Logs Tripwire 2 10 1 Introduction While Celery is written with security in mind it should be treated as an unsafe component Depending on your Security Policy there are various steps you can take to make your Celery installation more secure 2 10 Security 75 Celery Documentation Release 2 5 5 2 10 2 Areas of Concern Broker It is imperative that the broker is guarded from unwanted access especially if it is publically accesible By default workers trust that the data they get from the broker has not been tampered with See Message Signing for
470. yd The broadcast consumer is now closed if the connection is reset celeryd Now properly handles errors occurring while trying to acknowledge the message TaskRequest on_failure now encodes traceback using the current filesystem encoding Issue 286 EagerResult can now be pickled Issue 288 11 26 2 Documentation Adding Contributing Added Optimizing Added Security section to the FAQ 11 27 2 1 3 release date 2010 11 09 05 00 P M CEST Fixed deadlocks in timer2 which could lead to djcelerymon celeryev c hanging EventReceiver now sends heartbeat request to find workers This means celeryev and friends finds workers immediately at startup celeryev cursesmon Set screen_delay to 10ms so the screen refreshes more often Fixed pickling errors when pickling AsyncResul1t on older Python versions celeryd prefetch count was decremented by eta tasks even if there were no active prefetch limits 11 28 2 1 2 release data TBA 11 27 2 1 3 197 Celery Documentation Release 2 5 5 11 28 1 Fixes celeryd Now sends the task retried event for retried tasks celeryd Now honors ignore result for WorkerLostError and timeout errors celerybeat Fixed UnboundLocalError in celerybeat logging when using logging setup signals celeryd All log messages now includes exc_info 11 29 2 1 1 release date 2010 10 14 02 00 PM CEST 11 29 1 Fixes Now working on Windows again Removed dependency on the pwd grp modules

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