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Getting Started Guide - Community RTI Connext Users

1. sessseessesssssississesssrtissisresssesiesessesntesieriesennnestenieseesnesnes 4 2 4 1 1 When to Set the Discovery Peers ssssssssssessessersisrissesstenissississteniententessnsnenteneeseess 4 3 4 1 2 How to Set Your Discovery Peers cceccccseseesesesseseseseseseesecseeseseecseseeseeseeensees 4 3 4 2 Customizing Behavior QoS Configuration cece ceeescecesseseeneseceseneeeneseseeees 4 4 4 3 Compact Type Safe Data Programming with Data Types cccccccsseeetetetesesteteteneees 4 7 4 3 1 Using Built in Types secs civics deee i e ai i 4 10 4 3 2 Using Types Defined at Compile Time s sesssssssissssssessssisstsssesiesisstssserieseessessenens 4 11 4 3 3 Running with Dynamic Types se ssesssssessississsssissiestestsssessententisrnsnestentesresseneernt 4 19 5 Design Patterns for Rapid Development 5 1 Building and Running the Code Examples ccccccceccsssesescceeseneecsceeseseeceeeseneseseeenenes 5 2 5 2 Subscribing Only to Relevant Data cess eceeeeececeeeeseecsssseeesenesesesenesensseeeeees 5 3 5 2 1 Content Based Filtering rossini erino AE E EER EERE 5 5 5 2 2 Lifespan and History Depth ou eiie nioe aaiae aaas esis heee aae aei EE aeae 5 7 5 2 3 Time Based Filtern ginsis inate e EE E E dads 5 12 5 3 Accessing Historical Data when Joining the Network sssserssssssssssssterstesssesneentsessesnee 5 14 5 3 1 implementation ypssnngonipsnen a a a e a aa 5 15 5 3 2 Running amp Verifying ess
2. Remember that there is a strong analogy between DDS and relational Next we will change the history depth and lifespan duration in the file USER_QOS_PROFILES xml to see how the example s output changes Set the history depth to one Run the example again with the content based filter shown here in the Java example gt run sh sub f key CNN OR key Reuters You will only see articles from CNN and Reuters and only the last value published for each as of the end of the two second polling period Now set the history depth to 10 and decrease the lifespan to three seconds With these settings and at the rates used by this example the lifespan will always take effect before the history depth Run the example again this time without a content filter Notice how the subscribing application sees all of the data that was publishing during the last two second period as well as the data that was published in the latter half of the previous period Reduce the lifespan again this time to one second If you run the example now you will see no cached articles at all Do you understand why The subscribing application s polling period is two seconds so by the time the next poll comes everything seen the previous time has expired Subscribing Only to Relevant Data Figure 5 3 Using History and Lifespan Availoble articles as of 10 02 48 AM Available 10 02 47 AM From Reuters 10 02 47 AM From ONN 10 02 47 AM Fro
3. As with the Hello World example Java users should use the build and run command scripts in the directory Subscribing Only to Relevant Data 5 2 NDDSHOME example JAVA News Non Java Windows developers will find the necessary Microsoft Visual Studio solution files in the subdirectory NDDSHOME example lt language gt News win32 Appropriate makefiles for building the C C or Ada examples on UNIX platforms are located in the subdirectory NDDSHOME example lt language gt News make The News example combines the publisher and subscriber in a single program which is run from the NDDSHOME example lt language gt News directory with the argument pub or sub to select the desired behavior When running with default arguments you should see output similar to that shown in Figure 5 1 To see additional command line options run the program without any arguments Both the publishing application and the subscribing application operate in a periodic fashion l The publishing application writes articles from different news outlets at different rates Each of these articles is numbered consecutively with respect to its news outlet Every two seconds the publisher prints a summary of what it wrote in the previous period L The subscribing application polls the cache of its DataReader every two seconds and prints the data it finds there Many real world applications will choose to process data as soon as it arrives rather than po
4. merated durability kind For more information about this QoS policy consult the online API documentation Open ReadMe html and select the API documentation for your language then select Modules DDS API Reference Infrastructure QoS Policies For Ada open doc html api_ada index html and select Infrastructure Module DDSQosTypesModule 1 Ada support requires a separate add on product Ada 2005 Language Support for RTI Data Distribution Service 5 15 juowidojeasg pidpy 10 SUJ HOd UBISseq S 5 3 2 5 16 You can specify the QoS policies either in your application code or in one or more XML files Both mechanisms are functionally equivalent the News example uses the XML mechanism For more information see the chapter on Configuring QoS with XML in the RTI Data Distribution Service User s Manual Here is an example of how to configure the Durability QoS policy in a QoS profile lt durability gt lt kind gt TRANSIENT_ LOCAL DURABILITY QOS lt kind gt lt durability gt You can see this in the News example provided for C C Java and Ada in the file USER_QOS_PROFILES xml The above configuration indicates that the DataWriter should maintain data it has pub lished on behalf of later joining DataReaders and that DataReaders should expect to receive historical data when they join the network However if a DataWriter starts up publishes some data and then shuts down a DataReader that subsequen
5. Professional Edition Getting Started Guide for details If you are installing RTI Data Distribution Service independently not part of RTI Profes sional Edition the distribution is packaged in two or more tar gz files a host archive that contains documentation header files and other files you need for development and one or more target archives containing the libraries and other files you need for deployment Unpack them as described below You do not need to be logged in as root during installation 1 Make sure you have GNU s version of the tar utility which handles long file names On Linux systems this is the default tar executable On Solaris systems use gtar 2 Create a directory for RTI Data Distribution Service We will assume that you want to install under opt rti you may replace references to opt rti with the direc tory of your choice 3 Move the downloaded file s into your newly created directory We assume your distribution file is named rtidds45x i86Linux2 6gcc3 4 3 tar gz Your filename will be different depending on your architecture the x represents a release spe cific letter Installing RTI Data Distribution Service 4 Extract the host distribution first from the uncompressed files For example gunzip rtidds45x i86Linux2 6gcc3 4 3 tar gz gtar xvf rtidds45x i86Linux2 6gcc3 4 3 tar Repeat this step as necessary for your target archive files The names of these files will differ based on th
6. they need to discover each other By default RTI Data Distribution Service applications discover each other using shared memory or UDP loopback if they are on the same host or using multicast if they are on different hosts Therefore to run an application on two or more computers using multicast or on a single computer with a network connection no changes are needed They will dis cover each other automatically The chapter on Discovery in the RTI Data Distribution Service User s Manual describes the process in more detail If you want to use computers that do not support multicast or you need to use unicast for some other reason or if you want to run on a single computer that does not have a network connection in which case your operating system may have disabled your net work stack there is a simple way to control the discovery process you won t even have to recompile Application discovery can be configured through the NDDS_DISCOVERY_PEERS environment variable or in your QoS configuration file 1 With the exception of LynxOS On LynxOS systems multicast is not used for discovery by default unless NDDS_DISCOVERY_PEERS is set Automatic Application Discovery 4 1 1 When fo Set the Discovery Peers There are only a few situations in which you must set the discovery peers In the following replace N with the number of RTI Data Distribution Service applica tions you want to run 1 If you cannot use multicas
7. Data Distribution Service 5 7 juowidojeasg pidpy 10 SU1 Od UBISEg S Figure 5 2 Using a Content based Filter gt A A HORo Terminal ssh 60x45 T Terminal ssh 60x45 gt run sh pub d 13 gt run sh sub d 13 f key CNN OR key Reuters News Example Application News Example Application Copyright 2009 Real Time Innovations Inc Copyright 2009 Real Time Innovations Inc Articles published in Last period as of 10 02 49 AM Available articles as of 10 02 48 AM From Reuters Lorem ipsum 1 10 02 47 AM From Reuters Lorem ipsum 1 From AP Lorem ipsum 1 10 02 47 AM From CNN Lorem ipsum 1 From CNN Lorem ipsum 1 10 02 47 AM From Reuters Lorem ipsum 2 From Bloomberg Lorem ipsum 1 10 02 47 AM From Reuters Lorem ipsum 3 From NY Times Lorem ipsum 1 10 02 47 AM From Reuters Lorem ipsum 4 From Economist Lorem ipsum 1 10 02 47 AM From CNN Lorem ipsum 2 From Reuters Lorem ipsum 2 10 02 48 AM From Reuters Lorem ipsum 5 From Reuters Lorem ipsum 3 Available articles as of 10 02 50 AM From AP Lorem ipsum 2 10 02 47 AM From CNN Lorem ipsum 1 cached From Reuters Lorem ipsum 4 10 02 47 AM From CNN Lorem ipsum 2 cached From CNN Lorem ipsum 2 10 02 48 AM From Reuters Lorem ipsum 6 From Reuters Lorem ipsum 5 10 02 48 AM From Reuters
8. Investment ROI analysis is outside the scope of this document with RTI Data Distribution Service you get a rich set of high performance networking features by just turning on configuration parameters and often without writing a single line of additional code RTI has decades of experience with hundreds of applications This effort created an integrated and time tested architecture that seamlessly provides the flexibility you need to succeed now and grow into the future Many features require fundamental support in the core of the middleware and cannot just be cobbled onto an existing framework It would take many man years of effort to duplicate even a small subset of the functionality to the same level of stability and reliability as delivered by RTI For example some of the middleware functionality that your application can get by just enabling configuration parameter include L Tuning reliable behavior for multicast lossy and high latency networks L Supporting high data availability by enabling redundant data sources for example keep receiving data from source A If source A stops publish ing then start receiving data from source B and providing notifications when application enter or leave the network L Optimizing network and system resources for transmission of periodic data by supporting time based filtering of data example receive a sam ple no more than once per second and deadlines example expect
9. It requires no special server software or hardware Messaging Messaging Application Application Traditional message oriented middleware implementations require a broker to forward every message increasing latency and decreasing determinism and fault tolerance RTI s unique peer to peer architecture eliminates bottlenecks and single points of failure 1 For up to date performance benchmarks visit RTI on the web at http www rti com products dds benchmarks cpp linux html Why Choose RTI Data Distribution Service The design also delivers high reliability and availability with automatic failover config urable retries and support redundant publishers subscribers networks and more Publishers and subscribers can start in any order and enter and leave the network at any time the middleware will connect and disconnect them automatically RTI Data Dis tribution Service provides fine grained control over failure behavior and recovery as well as detailed status notifications to allow applications to react to situations such as missed delivery deadlines dropped connections and slow or unresponsive nodes The User s Manual has details on these and all other capabilities This guide only pro vides an overview Reduce Cost through Ease of Use and Simplified Deployment RTI Data Distribution Service helps keep development and deployment costs low by I Increasing developer productivity Easy to use standards compliant DD
10. Language Support for RTI Data Distribution Service Building and Running Hello World Hello vs2005 Microsoft Visual Studio File Edit Yiew Project Build Debug Tools Window Community Help gt Release gt Win32 Solution Explorer HelloPubli HelloSubscriber cpp HelloPublisher cpp amp a A E Unknown Scope a Solution Hello vs2005 2 projects EL PPAR RAAA AREA AERA AAA AAA A AAA ATA A ATTRA AAT ERATE EF HelloPublisher ic Copyright Real Time Innovations C HelloPublisher cpp jt A HelloSubscriber j Permission to modify and use for inte Ctt iber r zti HelloSubscriber PR This software is nrovided as is without wa C on UNIX based Systems To build the example applications 1 From your command shell go to NDDSHOME example CPP Hello_simple 2 Type gt gmake f make Makefile lt architecture gt where lt architecture gt is one of the supported architectures see the contents of the make directory for a list of available architectures If you do not see a makefile for your architecture please refer to Section 4 3 2 1 to learn how to generate a makefile or project files for your platform This command will build a release executable To build a debug version instead type gt gmake f make Makefile lt architecture gt DEBUG 1 Java Java on Windows Systems To build the example applications 1 From your command shell go
11. Module Lifespan and History Depth One of the most common ways to reduce data is to indicate for how long a data sample remains valid once it has been sent You can indicate such a contract in one or both of two ways in terms of a number of samples to retain the history depth and the elapsed time period during which a sample should be retained the lifespan For example you may be interested in only the most recent data value the so called last values or in all data that has been sent during the last second The history depth and lifespan which can be specified declaratively with QoS policies see below apply both to durable historical data sent to late joining subscribing appli cations as well as to current subscribing applications For example suppose a subscrib ing application has set history depth 2 indicating that it is only interested in the last two samples A publishing application sends four data samples in close succession and the middleware on the subscribing side receives them before the application chooses to read them from the middleware When the subscribing application does eventually call DataReader read it will see only samples 3 and 4 samples 1 and 2 will already have been overwritten If an application specifies both a finite history depth and a finite lifes pan whichever limit is reached first will take effect 1 Ada support requires a separate add on product Ada 2005 Language Support for RTI
12. Section 6 5 2 3 but is beyond the scope of this document 6 5 SOUDWJOLeg YIH 10 SUI HOd UBIseg 9 6 2 1 6 2 1 1 6 6 Implementation There are many variables to consider and finding the optimum values to the queue size and the right policy for the buffers depends on the type of data being exchanged the rate of which the data is written the nature of the communication between nodes and various other factors The RTI Data Distribution Service User s Manual dedicates an entire chapter to the reli ability protocol providing details on choosing the correct values for the QoS based on the system configuration For more information refer to Chapter 10 in the User s Man ual The following sections highlight the key QoS settings needed to achieve strict reliability In the reliable xml QoS profile file you will find many other settings besides the ones described here A detailed description of these QoS is outside the scope of this docu ment and for further information refers to the comments in the QoS profile and in the RTI Data Distribution Service User s Manual Enable Reliable Communication The QoS that control the kind of communication is the Reliability QoS of the DataWriter and DataReader lt datawriter_qos gt lt reliability gt lt kind gt RELIABLE_ RELIABILITY _QOS lt kind gt lt max_blocking_time gt lt sec gt 5 lt sec gt lt nanosec gt 0 lt nanosec gt lt max_blocking_time lt reliab
13. based application Then we ll take a step back to learn about the general concepts in the middleware and show how they are applied in the example application you ran This chapter includes E Building and Running Hello World LJ Data Distribution Service DDS 101 Next Chapter gt Chapter 4 Capabilities and Performance Building and Running Hello World Let s start by compiling and running Hello World a basic program that publishes infor mation over the network For now do not worry about understanding the code we start covering it in Chapter 4 Capabilities and Performance Use the following instructions to run your first middle ware program using RTI Data Distribution Service 3 1 PHOM OIISH 3 1 1 3 1 1 1 3 2 Step 1 Set Up the Environment There are a few things to take care of before you start working with the example code Set Up the Environment on Your Development Machine a Set the NDDSHOME environment variable Set the environment variable NDDSHOME to the RTI Data Distribution Service install directory RTI Data Distribution Service itself does not require that you set this environment variable It is used in the scripts used to build and run the example code because it is a simple way to locate the install directory You may or may not choose to use the same mechanism when you create scripts to build and or run your own applications e On UNIX based systems This location
14. for RTI Data Distribution Service 5 13 juowidojeasg pidpy 10 SUJ HOd UBISseq S 5 2 3 2 Running amp Verifying Figure 5 4 shows some of the output after activating the filter Figure 5 4 Using a Time based Filter a NOO Terminal ssh 60x45 rean AM From Economist loren ipsum 3 11 02 31 el Pe Reuters Loren ipsum 1 Ava cached Article 1 sent at 31 om A orem ipsum 1 cached 11 02 31 a From CNN Lorem ipsum 1 cached lt Article 1 sent at 31 702 rom Bloomberg orem ipsum 1 cached 11 02 31 i From NY Times Lorem Sea 1 Ccached FE me 2 aoe Article 6 sent at 32 ot o a sin Reuters lorem ipsum 6 cached Articles 2 5 filtered psum s cached Article 3 sent at 32 Lorem ipsum 3 cached lt Article 2 filtered 11 02 32 AM From CNN Because you set the time based filter to one second you will not see more than two updates for any single news outlet in any given period because the period is two sec onds long 5 3 Accessing Historical Data when Joining the Network In Section 5 2 you learned how to specify which data on the network is of interest to your application The same QoS parameters can also apply to late joining subscribers applications that subscribe to a topic after some amount of data has already been pub lished on that topic This concept storing sent data with
15. may be opt rti ndds 4 5x e On Windows systems This location may be C Program Files RTI ndds 4 5x The installer gave you the option to set this environment variable automati cally as part of the installation process If you have multiple versions of RTI Data Distribution Service installed As men tioned above RTI Data Distribution Service does not require that you have the environment variable NDDSHOME set at run time However if it is set the middleware will use it to load certain configuration files Additionally you may have previously set your path based on the value of that variable Therefore if you have NDDSHOME set be sure it is pointing to the right copy of RTI Data Distribution Service Update your path Add RTI Data Distribution Service s scripts directory to your path This will allow you to run some of the simple command line utilities included in your distribu tion without typing the full path to the executable e On UNIX based systems Add the directory to your PATH environment vari able e On Windows systems Add the directory to your Path environment variable The installer gave you the option to set this environment variable automati cally as part of the installation process If you will be using the separate add on product Ada 2005 Language Support for RTI Data Distribution Service Add NDDSHOME lib gnat to your ADA_PROJECT_PATH environment vari able This directory contains Ada project fi
16. mix and match them these approaches interoperate with each other and across programming languages and platforms So your options are I Use the built in types If a message is simply a string or a buffer of bytes you can use RT s built in types described in Using Built in Types Section 4 3 1 Define a type at compile time using a language independent description lan guage and the RTI code generator rtiddsgen as described in Using Types Defined at Compile Time Section 4 3 2 This approach offers the strongest compile time type safety Whereas in house middleware implementation teams often define data formats in word processing or spreadsheet documents and translate those formats into application code by hand RTI relies on standard type definition formats that are both human and machine readable and generates code in compliance with open international standards The code generator accepts data type definitions in a number of formats to make it easy integrate RTI Data Distribution Service with your development processes and IT infrastructure e OMG IDL This format is a standard component of both the DDS and CORBA specifications It describes data types with a C like syntax This format is described in Chapter 3 of the User s Manual 4 9 SOUDUWIO Ied PUD s yi qodo vy 4 3 1 4 10 e XML schema XSD whether independent or embedded in a WSDL file XSD may be the format of choice for those using RTI Data Distr
17. persistence service shut down or fail the durable data they were maintaining will be lost This level of durability provides a higher level of fault tolerance and availability than does transient local durability without the performance or management overhead of a database I Persistent Data that has been sent may be relevant to late joining subscribers and will be stored externally to the DataWriter that produced that data in a relational database This level of durability requires one or more instances of the RTI Persis tence Service on your network It provides the greatest degree of assurance for your most critical data streams because even if all data writers and all persis tence server instances fail your data can nevertheless be restored and made available to subscribers when you restart the persistence service As you can see the level of durability indicates not only whether historical data will be made available to late joining subscribers it also indicates the level of fault tolerance with which that data will be made available Learn more about durability including the RTI Persistence Service by reading the chapter on Mechanisms for Achieving Information Durability and Persistence in the RTI Data Distribution Service User s Manual Implementation To configure data durability use the Durability QoS policy on your DataReader and or DataWriter The degrees of durability described in Section 5 3 are represented as an enu
18. publishing application Java As described above you should have already set your path appropriately so that the example application can load the native libraries on which RTI Data Dis tribution Service depends If you have not you can set the variable RTILEXAMPLE_ARCH in your command shell e g to i86Win32jdk or i86Linux2 6gcc4 1 1 jdk and the example launch scripts will use it to set your path for you L On a Windows system From a different command shell go to NDDSHOME example JAVA Hello_simple and type gt runPub I On a UNIX based system From a different command shell go to NDDSHOME example J AVA Hello_simple and type gt runPub sh Ada To start the publishing application Ada L On a UNIX based system From a different command shell go to example ADA Hello_simple and type gt objs lt architecture gt hellopublisher 1 Ada support requires a separate add on product Ada 2005 Language Support for RTI Data Distribution Service 3 10 Data Distribution Service DDS 101 Where lt architecture gt is one of the supported architectures see the contents of the make directory for a list of available architectures For example the architecture name corresponding to Red Hat Enterprise Linux 5 5 is i86Linux2 6gcc4 1 2 If you typed Hello World in the publishing application you should see output similar to the following lo x RTI ndas 4 4c examp le CPP Hel lo_simp e gt 0
19. read take one instance at a time For more information about keys and instances see Section 2 2 2 Samples Instances and Keys in the RTI Data Distribution Service User s Manual 1 Ada support requires a separate add on product Ada 2005 Language Support for RTI Data Distribution Service 5 17 juowidojeasg pidpy 10 SUJ HOd UBISeq S 5 4 1 Implementation The call to read looks like this in C DDS_ReturnCode_t result _reader gt read CH articles 111 in data here articleInfos fill in parallel meta data here DDS_LENGTH_UNLIMITED any articles DDS_ANY_SAMPLE_ STATE DDS_ANY_VIEW_STATE DDS_ANY_INSTANCE_STATE if result DDS_RETCODE_NO_DATA nothing to read go back to sleep if result DDS RETCODE OK an error occurred stop reading throw std runtime_error A read error occurred result Process data _reader gt return_loan articles articleInfos It looks like this in Java Tew Java _reader read articles 111 in data here articleInfos fill in parallel meta data here ResourceLimitsQosPolicy LENGTH_ UNLIMITED any articles SampleStateKind ANY_SAMPLE_ STATE ViewStateKind ANY_VIEW_STATE InstanceStateKind ANY_INSTANCE_STATE Process data catch RETCODE_NO_DATA noData nothing to read go back to sleep catch RETCODE_ ERROR ex an error occurred stop reading throw ex Herina linya _read
20. see the content of the make directory for a list of available architectures For example the architecture name corresponding to Red Hat Enterprise Linux 5 5 is i86Linux2 6gcc4 1 2 3 1 4 Step 4 Start the Publisher RTI Data Distribution Service interoperates across all of the programming languages it supports so you can choose whether to run the publisher in the same language you chose for the subscriber or a different language 1 Ada support requires a separate add on product Ada 2005 Language Support for RTI Data Distribution Service 3 9 PHOM OIISH am C To start the publishing application L On a Windows system From a different command shell go to NDDSHOME example CPP Hello_simple and type gt objs lt architecture gt HelloPublisher exe where lt architecture gt is one of the supported architectures see the contents of the win32 directory for a list of available architectures For example the Windows architecture name corresponding to 32 bit Visual Studio 2005 is i86Win32VS2005 J On a UNIX based system From a different command shell go to NDDSHOME example CPP Hello_simple and type gt objs lt architecture gt HelloPublisher where lt architecture gt is one of the supported architectures see the contents of the make directory for a list of available architectures For example the architecture name corresponding to Red Hat Enterprise Linux 5 is i86Linux2 6gcc4 1 1 Java To start the
21. sup port rtiicom Navigate to Code Examples and search for Asynchronous Publication 1 FlowControllers are not supported when using Ada 2005 Language Support for RTI Data Distribution Ser vice 6 17 SOUDWJOLed YIH 10 SUI HOd UBIseg 9 6 4 1 2 6 4 1 3 Acknowledge and Repair Efficiently Piggyback heartbeat with each sample A DataWriter sends heartbeats meta data messages announcing available data and requesting acknowledgement in two ways periodically and piggybacked into application data packets Piggybacking heartbeats aggressively ensures that the middleware will detect packet losses early while allowing you to limit the number of extraneous network sends related to periodic heartbeats lt datawriter_qos gt lt resource_limits gt lt Used to configure piggybacks w o batching gt lt max_samples gt 20 lt An arbitrary finite size gt lt max_samples gt lt resource_limits gt lt writer_resource_limits gt lt Used to configure piggybacks w batching see below gt lt max_batches gt 20 lt An arbitrary finite size gt lt max_batches gt lt writer_resource_limits gt lt protocol gt lt rtps_reliable_writer gt lt heartbeats_per_max_samples gt 20 lt Set same as max_samples gt lt heartbeats_per_max_samples gt lt rtps_reliable_ writer gt lt protocol gt lt datawriter_qos gt The heartbeats_per_max_samples parameter controls ho
22. the current version of RTI Data Distribution Service If you are upgrading from a previous version read this document first l Release Notes and Platform Notes RTII_DDS_ReleaseNotes pdf and RTI_DDS_PlatformNotes pdf These documents provide system requirements compatibility and other platform specific information about the product includ ing specific information required to build your applications using RTI Data Distri bution Service such as compiler flags and libraries L User s Manual RTI_DDS_UsersManual pdf This document describes the fea tures of the product and how to use them It is organized around the structure of the DDS APIs and certain common high level tasks uoljojueWUNDOGg SIQDIIDAY Z L API Documentation ReadMe html RTI_DDS_ApiReference lt Language gt pdf This extensively cross referenced documentation available both in HTML and printable PDF formats is your in depth reference to every operation and configu ration parameter in the middleware Even experienced RTI Data Distribution Ser vice developers will often consult this information The Programming How To s available from the main page for C C Java and NET provide example code These are hyperlinked code snippets to the full API documentation and provide a good place to begin learning the APIs Start by reviewing the Publication Example and Subscription Example which provide step by step examples of how to send and receive data wit
23. to NDDSHOME example JAVA Hello_simple 2 Lype gt build PHOM OII H E Java on UNIX based Systems To build the example applications 1 From your command shell go to NDDSHOME example J AVA Hello_simple 2 Type gt build sh Cada Ada on UNIX based Systems To build the example applications 1 From your command shell go to NDDSHOME example ADA Hello_simple 2 Type gt gmake f make Makefile lt architecture gt where lt architecture gt is one of the supported architectures see the contents of the make directory for a list of available architectures If you do not see a makefile for your architecture please refer to Section 4 3 2 1 to learn how to generate a make file or project files for your platform This command will build a release execut able To build a debug version instead gt gmake f make Makefile lt architecture gt DEBUG 1 3 1 3 Step 3 Start the Subscriber C To start the subscribing application On a Windows system From your command shell go to NDDSHOME example CPP Hello_simple and type gt objs lt architecture gt HelloSubscriber exe where lt architecture gt is one of the supported architectures see the contents of the win32 directory for a list of available architectures For example the Windows architecture name corresponding to 32 bit Visual Studio 2005 is i86Win32VS2005 L On a UNIX based system From your command shell go to NDDSHOM
24. will see the throughput more closely approach the theoretical throughput of your network By batching multiple data samples into a single network packet as the high throughput example QoS profile does you should be able to saturate a gigabit Ethernet network with samples sizes as small as 100 200 bytes Without batching samples you should be able to saturate the network with samples of a few kilo bytes The difference is due to the performance limitations of the network trans port enterprise class platforms with commodity Ethernet interfaces can typically execute tens of thousands of send s per second In contrast saturating a high throughput network link with data sizes of less than a kilobyte requires hundreds of thousands of samples per second Is this the best possible performance The performance of an application depends heavily on the operating system the net work and how it configures and uses the middleware This example is just a starting point tuning is important for a production application RTI can help you get the most out of your platform and the middleware To get a sense for how an application s behavior changes with different QoS contracts try the other provided example QoS profiles and see how the printed results change Reliable Messaging Packets sent by a middleware may be lost by the physical network or dropped by rout ers Switches and even the operating system of the subscribing applications when bu
25. 1 6 Windows XP Pentium This process is commonly called serialization deserializa tion or marshalling demarshalling Messaging products have typically taken one of two approaches to this problem I Do nothing With this approach the middleware does not provide any help and user code must take into account memory layout differences when sending mes sages from one platform to another The middleware treats messages as an opaque buffer of bytes The JMS BytesMessage is an example of this approach 4 7 SOUDUWNOLISd PUD s yi qodo vy L Send everything every time Self describing messages are at the opposite extreme and embed full reflective information including data types and field names with each message The JMS MapMessage and the messages in TIBCO Rendezvous are examples of this approach The do nothing approach is lightweight on its surface but forces you the user of the middleware API to consider all data encoding alignment and padding issues The send everything alternative results in large amounts of redundant information being sent with every packet impacting performance Figure 4 1 Self Describing Messages vs Type Definitions Self Describing Messages Automatic Discovery type string Symbol text Price float SSS Oe kx Network RTI Data Distribution Service exchanges data type definitions such as field names and types once at application start up time This increases perfo
26. 1 second which makes such a connection unsuitable for applications or mid dleware tuned for low latency real time behavior In addition satellite links typically have lower bandwidth with near symmetric connection throughput of around 250 500 Kb s and an advertised loss of approximately 3 of network packets Of course the throughput numbers will vary based on the modem and the satellite service In light of 6 13 SOUDWWIOLeg YIH 10 SUI HOd UBIseg 9 6 4 1 6 4 1 1 6 14 these facts a distributed application needs to tune the middleware differently when sending data over such networks RTI Data Distribution Service is capable of maintaining liveliness and application level QoS even in the presence of sporadic connectivity and packet loss at the transport level an important benefit in mobile or otherwise unreliable networks It accomplishes this by implementing a reliable protocol that not only sequences and acknowledges applica tion level messages but also monitors the liveliness of the link Perhaps most impor tantly it allows your application to fine tune the behavior of this protocol to match the characteristics of your network Without this latter capability communication parame ters optimized for more performant networks could cause communication to break down or experience unacceptable blocking times a common problem in TCP based solutions Implementation When designing a system that demands reliability over
27. 19 SOUDUNOLISd PUD SseIIIGodDd y 4 20 Chapter 5 Design Patterns for Rapid Development In this chapter you will learn how to implement some common functional design pat terns As you have learned one of the advantages to using RTI Data Distribution Service is that you can achieve significantly different functionality without changing your application code simply by updating the XML based Quality of Service QoS parame ters In this chapter we will look at a simple newspaper example to illustrate these design patterns Newspaper distribution has long been a canonical example of publish sub scribe communication because it provides a simple metaphor for real world problems in a variety of industries A radar tracking system and a market data distribution system share many features with the news subscriptions we are all familiar with many to many publish subscribe communication with certain quality of service requirements 5 1 juowidoyjeasg pidpy 10 suleyjog uBIseq S 5 1 5 2 In a newspaper scenario provided in an example called News example for all lan guages a news publishing application distributes articles from a variety of news out lets CNN Bloomberg etc on a periodic basis However the period differs from outlet to outlet One or more news subscribers poll for available articles also on a peri odic basis and print out their contents Once published articles remain available for a perio
28. AM 10 02 50 AM From Reuters Lorem ipsum 16 From Reuters Lorem ipsum 12 10 02 50 AM From CNN Lorem ipsum 6 2 2 1 5 8 Publishing Application Implementation Subscribing Application History depth is part of the History QoS policy The lifespan is specified with the Lifes pan QoS policy The History QoS policy applies independently to both the DataReader and the DataWriter the values specified on both sides of the communication need not agree The Lifespan QoS policy is specified only on the DataWriter but it is enforced on both sides the DataReader will enforce the lifespan indicated by each DataWriter it discovers for each sample it receives from that DataWriter For more information about these QoS policies consult the online API documentation Open ReadMe html and select the API documentation for your language then select Modules DDS API Reference Infrastructure QoS Policies For Ada open doc html api_ada index html and select Infrastructure Module DDSQosTypesModule 1 Ada support requires a separate add on product Ada 2005 Language Support for RTI Data Distribution Service Subscribing Only to Relevant Data 5 2 2 1 1 You can specify these QoS policies either in your application code or in one or more XML files Both mechanisms are functionally equivalent the News example provided for C C Java and Ada uses XML files For more information about this mechanism see the cha
29. Current Throughput start sampLes sampLes samples smpls sec Ismpls sec Mbps 1 3984 3984 00 3984 00 31 09 2 8112 4056 00 4128 00 32 22 3 12096 4932 08 3984 00 31 09 4 16128 4932 08 4932 20 31 47 5 20112 4022 40 3984 00 31 09 6 24144 4 4024 00 4932 08 31 47 7 28176 4925 14 4932 08 31 47 8 32160 4020 00 3984 00 31 09 9 36432 4048 00 4272 08 33 34 10 42800 4080 00 4368 00 34 09 11 45168 4106 18 4368 00 34 09 12 49536 4128 00 4368 00 34 09 13 53904 4146 46 4368 00 34 09 14 58272 4162 29 4368 00 34 09 15 62304 4153 68 4032 08 31 47 16 66288 d 4143 08 3984 00 31 09 17 70320 4136 47 4032 00 31 47 You can find the source for the Hello_builtin example for Java in NDDSHOME example JAVA Hello_builtin the equivalent source code in other supported languages is in the directories NDDSHOME example lt language gt The Hello_idl and Hello_dynamic examples are in parallel directories under NDDSHOME example lt language gt The examples perform these steps 1 Parse their command line arguments 2 Check if the Quality of Service QoS file can be located The XML file that sets the Quality of Service QoS parameters is either loaded from the file USER_QOS_PROFILES xml in the current directory of the pro gram or from the environment variable NDDS_QOS_PROFILES For more Building and Running the Code Examples information on how to use QoS profiles see the ch
30. DataWriter level deadline specified inside the file s datareader_qos or datawriter_qos elements respectively possibly because you previously modified the configuration in Section 5 2 3 it is overriding the topic level configuration Be careful that you don t modify a deadline specification that will only be overridden later and not take effect You will see output similar to Figure 5 5 Figure 5 5 Using a Shorter Deadline QOO Terminal ssh 60x9 11 22 41 AM From AP lorem ipsum 39 11 22 41 AM From Bloomberg lorem ipsum 20 gt Callback requested deadline missed Economist gt Callback requested deadline missed NY Times gt Callback requested deadline missed Economist gt Callback requested deadline missed NY Times 0 Available articles as of 11 22 43 AM 4 11 22 37 AM From CNN Lorem ipsum 20 cached w 11 22 38 AM From CNN Lorem ipsum 21 cached 5 26 Chapter 6 Design Patterns for High Performance In this chapter you will learn how to implement some common performance oriented design patterns As you have learned one of the advantages to using RTI Data Distribu tion Service is that you can easily tune your application without changing its code sim ply by updating the XML based Quality of Service QoS parameters We will build on the examples used in Building and Running Hello World Section 3 1 to demonstrate the different use cases The example applications Hello_bui
31. Distribution Service 3 2 PHOM OIISH E You can create a Topic with the following C code CH topic participant gt create_topic Hello World Topic name DDSStringTypeSupport get_type_name Type name DDS_TOPIC_QOS_DEFAULT Topic Qos NULL elie site Tro DDS_STATUS_MASK_NONE Besides the new Topic s name and type an application specifies three things I A suggested set of QoS for DataReaders and DataWriters for this Topic I A listener and listener mask that indicate which events the application wishes to be notified of if any In this case the Topic s type is a simple string a type that is built into the middleware Let s see the same logic in Java Topic topic participant create_topic Java Hello World StringTypeSupport get_type_name DomainParticipant TOPIC_QOS_DEFAULT QoS raed AL Listener StatusKind STATUS_MASK_NONE In Ada it looks like this Ada topic participant Create_Topic DDS To_DDS_Builtin_String Hello World Topic name DDSStringTypeSupport Get_Type Name Type name DDS DomainParticipant TOPIC_QOS_DEFAULT Topic QoS null Listener DDS STATUS_MASK_NONE 1 Ada support requires a separate add on product Ada 2005 Language Support for RTI Data Distribution Service 3 22 Data Distribution Service DDS 101 3 2 6 Keys and Samples The data values associated with a Topic can change
32. E example CPP Hello_simple and type gt objs lt architecture gt HelloSubscriber 1 Ada support requires a separate add on product Ada 2005 Language Support for RTI Data Distribution Service 3 8 Building and Running Hello World where lt architecture gt is one of the supported architectures see the contents of the make directory for a list of available architectures For example the architecture name corresponding to Red Hat Enterprise Linux 5 is i86Linux2 6gcc4 1 1 Java To start the subscribing application Java As described above you should have already set your path appropriately so that the example application can load the native libraries on which RTI Data Dis tribution Service depends If you have not you can set the variable RTILEXAMPLE_ARCH in your command shell e g to i86Win32jdk or i86Linux2 6gcc4 1 1 jdk and the example launch scripts will use it to set your path for you fi On a Windows system From your command shell go to NDDSHOME example JAVA Hello_simple and type gt runSub L On a UNIX based system From your command shell go to NDDSHOME example J AVA Hello_simple and type gt runSub sh Ada To start the subscribing application Ada L On a UNIX based system From your command shell go to NDDSHOME example ADA Hello_simple and type gt objs lt architecture gt hellosubscriber Where lt architecture gt is one of the supported architectures
33. Lorem ipsum 7 From AP Lorem ipsum 3 10 02 48 AM From CNN Lorem ipsum 3 From Bloomberg Lorem ipsum 2 10 02 48 AM From Reuters Lorem ipsum 8 From Reuters Lorem ipsum 6 10 02 48 AM From Reuters Lorem ipsum 9 From NY Times Lorem ipsum 2 10 02 49 AM From Reuters Lorem ipsum 10 From Reuters Lorem ipsum 7 10 02 49 AM From CNN Lorem ipsum 4 From AP Lorem ipsum 4 10 02 49 AM From Reuters Lorem ipsum 11 From CNN Lorem ipsum 3 10 02 49 AM From Reuters Lorem ipsum 12 From Economist Lorem ipsum 2 10 02 49 AM From Reuters Lorem ipsum 13 From Reuters Lorem ipsum 8 10 02 49 AM From CNN Lorem ipsum 5 From Reuters Lorem ipsum 9 10 02 49 AM From Reuters Lorem ipsum 14 From AP Lorem ipsum 5 10 02 50 AM From Reuters Lorem ipsum 15 From Bloomberg Lorem ipsum 3 0 Available articles as of 10 02 52 AM From Reuters Lorem ipsum 10 10 02 47 AM From CNN Lorem ipsum 1 cached From CNN Lorem ipsum 4 10 02 47 AM From CNN Lorem ipsum 2 cached From Reuters Lorem ipsum 11 10 02 48 AM From CNN Lorem ipsum 3 cached From AP Lorem ipsum 6 10 02 49 AM From CNN Lorem ipsum 4 cached From NY Times Lorem ipsum 3 10 02 49 AM From CNN Lorem ipsum 5 cached Articles published in Last period as of 10 02 51
34. ORY_QOS lt kind gt lt history gt lt datawriter_qos gt lt datareader_qos gt lt history gt lt kind gt KEEP_ALL_HISTORY_QOS lt kind gt lt history gt lt datareader_qos gt The above section of the QoS profile tells RTI to use the policy KEEP_ALL for both DataReader and DataWriter 6 7 SOUDWJOLeg YIH 10 SUI HOd UBIseg 9 6 2 1 3 6 8 Controlling Middleware Resources With the ResourceLimits QosPolicy you have full control over the amount of memory used by the middleware In the example below we specify that both the reader and writer will store up to 10 samples if you use a History kind of KEEP_LAST the values specified here must be consistent with the value specified in the History s depth lt datawriter_qos gt lt resource_limits gt lt max_samples gt 10 lt max_samples gt lt resource_limits gt lt datawriter_qos gt lt datareader_qos gt lt resource_limits gt lt max_samples gt 2 lt max_samples gt lt resource_limits gt lt datareader_qos gt The above section tells RTI to allocate a buffer of 10 samples for the DataWriter and 2 for the DataReader If you do not specify any value for max_samples the default behavior is for the middleware to allocate as much space as it needs One important function of the Resource Limits policy when used in conjunction with the Reliability and History policies is to govern how far ahead of its DataReaders a DataWriter may
35. RTI Data Distribution Service Core Libraries and Utilities Getting Started Guide Version 4 5 This Guide describes how to download and install RTI Data Distribution Service It also lays out the core value and concepts behind the product and takes you step by step through the creation of a simple example application Developers new to RTI should read this document RTO The Global Leader in DDS 2004 2011 Real Time Innovations Inc All rights reserved Printed in U S A First gaa 3 re T4 October 2011 Trademarks Real Time Innovations and RTI are registered trademarks of Real Time Innovations Inc All other trademarks used in this document are the property of their respective owners Copy and Use Restrictions No part of this publication may be reproduced stored in a retrieval system or transmitted in any form including electronic mechanical photocopy and facsimile without the prior written permission of Real Time Innovations Inc The software described in this document is furnished under and subject to the RTI software license agreement The software may be used or copied only under the terms of the license agreement Technical Support Real Time Innovations Inc 385 Moffett Park Drive Sunnyvale CA 94089 Phone 408 990 7444 Email support rti com Website https support rti com Contents 1 Welcome to RTI Data Distribution Service 1 1 1 2 Why Choose RTI Data Distribution Service ccccc
36. Reader This QoS policy affects the Reliability and Durability QoS policies When a DataWriter sends data or a DataReader receives data the data sent or received is stored in a cache whose contents are controlled by the History QosPolicy The History QosPolicy can tell the middleware to store all of the data that was sent or received or only store the last n values sent or received If the History QosPolicy is set to keep the last n values only then after n values have been sent or received any new data will overwrite the oldest data in the queue The queue thus acts like a circular buffer of length n This QoS policy interacts with the Reliability QosPolicy by controlling whether or not the middleware guarantees that a all of the data sent is received using the KEEP_ALL setting of the History QosPolicy or b that only the last n data values sent are received a reduced level of reliability using the KEEP_LAST set ting of the History QosPolicy See the Reliability QosPolicy for more informa tion Also the amount of data sent to new DataReaders whose Durability QosPolicy see below is set to receive previously published data is controlled by the His tory QosPolicy 4 5 SOUDUWNOLISd PUD s yi qodo vy LL Lifespan Specifies how long the middleware should consider data sent by a user application to be valid The middleware attaches timestamps to all data sent and received When you specify a finite Lifespan for your da
37. S APIs get your code running quickly DDS is the established middleware standard for real time publish subscribe communication in the defense industry and is expanding rapidly in utilities transportation intelligence finance and other commercial industries LJ Simplifying deployment RTI Data Distribution Service automatically discovers connections so you don t need to configure or manage server machines or pro cesses This translates into faster turnaround and lower overhead for your deployment and administration needs L Reducing hardware costs Traditional messaging products require dedicated servers or acceleration hardware in order to host brokers The extreme efficiency and reduced overhead of RTI s implementation on the other hand allows you to achieve the same performance using standard off the shelf hardware with fewer machines than the competition Ensure Success with Unmatched Flexibility Out of the box RTI is configured to achieve simple data communications However when you need it RTI provides a high degree of fine grained low level control over the middleware including L The volume of meta traffic sent to assure reliability L The frequencies and time outs associated with all events within the middleware L The amount of memory consumed including the policies under which addi tional memory may be allocated by the middleware QWOTIOM L RTI s unique and powerful Quality of Service QoS policies can b
38. The News example does not actually install a DataWriterListener See the section on requested deadlines below the DataWriterListener works in a way that s parallel to the DataReaderListener Requested Deadlines The DataReader declares that it expects to receive at least one data sample of each instance within a given period using the Deadline QoS policy See the example XML configuration above If the declared deadline period elapses since the DataReader received the last sample of some instance that reader s listener if any will be invoked The listener s on_requested_deadline_missed will receive a call informing the application of the missed deadline To install a DataReaderListener in C DDSDataReader reader participant gt create_datareader aie EGIL DDS_DATAREADER_QOS_DEFAULT amp _listener listener DDS_STATUS_MASK ALL all callbacks reader NULL throw std runtime_error Unable to create DataReader In Java it looks like this DataReader reader participant create_datareader aie topic Subscriber DATAR EADER_QOS_ DEFAULT new ArticleDeliveryStatusListener listener StatusKind STATUS_ MASK ALL reader null all callbacks throw new IllegalStateException Unable to create DataReader 5 23 juowidojeasg pidpy 10 SUJ HOd UBISeq S And in Ada readerListener ArticleDeliveryStatusListener Ref_Access begin rea
39. UDUWHO ed PUD s yi qodo vy In this second publishing command window you should see Writing HelloWorld count 0 Writing HelloWorld count 1 Writing HelloWorld count 2 Look back in the first subscribing command window You should see that the sub scriber is now receiving messages from the publisher HelloWorld subscriber sleeping for 4 sec msg Hello World 0 HelloWorld subscriber sleeping for 4 sec msg Hello World 1 HelloWorld subscriber sleeping for 4 sec msg Hello World 2 4 3 2 3 3 Running the Generated Ada Example Ada support requires a separate add on product Ada 2005 Language Support for RTI Data Distribution Service First start the subscriber application helloworld_idl_file helloworld_subscriber Ada samples bin helloworld_idl_file helloworld_subscriber In this command window you should see that the subscriber wakes up every four sec onds to print a message HelloWorld subscriber sleeping for 4 000000000 sec HelloWorld subscriber sleeping for 4 000000000 sec HelloWorld subscriber sleeping for 4 000000000 sec Next open another command prompt window and start the publisher application helloworld_idl_file helloworld_publisher For example samples bin helloworld_idl_file helloworld_publisher In this second publishing command window you should see Writing HelloWorld count 0 Writing HelloWorld count 1 Writing HelloWorld count 2 4 18 Co
40. _RequestedDeadlineMissedStatus amp status DDS_KeyedString keyHolder DSKeyedStringDataReader typedReader DDSKeyedStringDataReader narrow reader typedReader gt get_key_value keyHolder status last_instance_handle std cout lt lt gt Callback requested deadline missed lt lt keyHolder key lt lt std endl oe void ArticleDeliveryStatusListener on_requested_ deadline missed 0 In Java z public void on requested deadline _ missed Java DataReader reader RequestedDeadlineMissedStatus status KeyedString keyHolder new KeyedString reader get_key_value_untyped keyHolder status last_instance_handle System out println gt Callback requested deadline missed keyHolder key And in Ada procedure On_Requested_ Deadline Missed Ada Self not null access Ref The Reader in DDS DataReader Ref Class Status in DDS RequestedDeadlineMissedStatus is pragma Unreferenced Self pragma Unreferenced The Reader pragma Unreferenced Status begin Put_Line gt Callback requested deadline missed end On_Requested_Deadline Missed 5 25 juowidojeasg pidpy 10 suleyjog uBIseq S 5 5 2 Running amp Verifying Modify the file USER_QOS_PROFILES xml to decrease the deadline to one second lt deadline gt lt period gt lt sec gt 1 lt sec gt lt nanosec gt 0 lt nanosec gt lt period gt lt deadline gt Note that if you have a DataReader or
41. a network that is lossy and has high latency and low throughput it is critical to consider J How much data you send at one time g your sample or batch size I How often you send it I The tuning of the reliability protocol for managing meta and repair messages It is also important to be aware of whether your network supports multicast communi cation if it does not you may want to explicitly disable it in your middleware configu ration e g by using the NDDS_DISCOVERY_PEERS environment variable or setting the initial_peers and multicast_receive_address in your Discovery QoS policy see the online API documentation Managing Your Sample Size Pay attention to your packet sizes to minimize or avoid IP level fragmentation Frag mentation can lead to additional repair meta traffic that competes with the user traffic for bandwidth Ethernet like networks typically have a frame size of 1500 bytes on such networks sample sizes or sample fragment sizes if you ve configured RTI Data Distri bution Service to fragment your samples should be kept to approximately 1400 bytes or less Other network types will have different fragmentation thresholds The exact size of the sample on the wire will depend not only on the size of your data fields but also on the amount of padding introduced to ensure alignment while serializ ing the data Streaming Data over Unreliable Network Connections Figure 6 7 shows how an application s effect
42. acts between data producers DataWriters and consumers DataReaders producers offer and consumers request levels of service The middleware is responsible for determining if the offer can satisfy the request thereby establishing the communication or indicating an incompatibility error Ensuring that participants meet the level of service contracts guarantees predictable operation For example I Periodic producers can indicate the speed at which they can publish by offering guaranteed update deadlines By setting a deadline a producer promises to send updates at a minimum rate Consumers may then request data at that or any slower rate If a consumer requests a higher data rate than the producer offers the middleware will flag that pair as incompatible and notify both the publishing and subscribing applications L Producers may offer different levels of reliability characterized in part by the number of past data samples they store for retransmission Consumers may then request differing levels of reliable delivery ranging from fast but unreliable best effort to highly reliable in order delivery This provides per data stream reliability control A single producer can support consumers with different levels of reliability simultaneously Other QoS policies control when the middleware detects nodes that have failed set delivery order attach user data prioritize messages set resource utilization limits partition the system into namespace
43. ages and networking transport protocols RTI Data Distribution Service is highly configurable so programmers can adapt it to meet an application s specific communica tion requirements An Overview of DDS Objects The primary objects in RTI Data Distribution Service are LI DomainParticipants k Publishers and DataWriters LI Subscribers and DataReaders LI Topics L Keys and Samples DDS Components Data Distribution Service DDS 101 3 2 2 Java DomainParticipants A domain is a concept used to bind individual applications together for communication To communicate with each other DataWriters and DataReaders must have the same Topic of the same data type and be members of the same domain Each domain has a unique integer domain ID Applications in one domain cannot subscribe to data published in a different domain Multiple domains allow you to have multiple virtual distributed systems on the same physical network This can be very useful if you want to run multiple independent tests of the same applications You can run them at the same time on the same network as long as each test runs in a different domain Another typical configuration is to isolate your development team from your test and production teams you can assign each team or even each developer a unique domain DomainParticipant objects enable an application to exchange messages within DDS domains An application must have a DomainParticipant
44. and KeyedOctets can be used to send variable length arrays of bytes These built in types may be sufficient if your data type needs are simple If your data is more complex and highly structured or you want DDS to examine fields within the data for filtering or other purposes this option may not be appropriate and you will need to take additional steps to use compile time types see Using Types Defined at Compile Time Section 4 3 2 or dynamic types see Running with Dynamic Types Sec tion 4 3 3 1 Dynamic types are not supported when using the separate add on product Ada 2005 Language Support for RTI Data Distribution Service Compact Type Safe Data Programming with Data Types 4 3 2 4 3 2 1 Using Types Defined at Compile Time In this section we define a type at compile time using a language independent descrip tion and the RTI code generator rtiddsgen The code generator accepts data type definitions in a number of formats such as OMG IDL XML Schema XSD and a DDS specific format of XML This makes it easy inte grate RTI Data Distribution Service with your development processes and IT infrastruc ture In this chapter we will define types using IDL In case you would like to experiment with a different format rtiddsgen can convert from any supported format to any other simply pass the arguments convertToldl convertToXml convertToXsd or convertToWsdl The following sections will take your through
45. and largely do not depend on the operating system either Header files for C and C APIs specification files for Ada Java runtime environment files used by the rtiddsgen tool you do not need to use this JRE to run your own Java applications Library files Ada project files Ada libraries and library information files Start page for accessing the HTML documentation Document format definitions and template files used by rtiddsgen RTI tools this directory should be in your path The two most important directories for learning RTI Data Distribution Service are exam ple and doc The doc directory contains the RTI Data Distribution Service library informa tion in PDF and HTML formats You may want to bookmark the HTML directory since you will be referring to this page a lot as you explore the RTI technology platform Example code is shipped in C C C Java and Ada You can access the example code in a language of your choice from the respective locations under the example direc tory These examples include L Hello_simple This example demonstrates one of the simplest applications you can write with RTI Data Distribution Service it does nothing but publish and sub scribe to short strings of text This example is described in detail in Chapter 3 Getting Started with RTI Data Distribution Service 1 Hello_builtin Hello_idl Hello dynamic These examples demonstrate more some of the unique capabilities of RTI Data Distr
46. anguage Ada example i86Linux2 6gcc4 1 2 replace HelloWorld idl Notes Ada support requires a separate add on product Ada 2005 Language Support for RTI Data Distribution Service l The generated publisher and subscriber source files are under the samples direc tory There are two generated project files one at the top level and one in the samples directory The project file in the samples directory samples helloworld samples gpr should be the one that you will use to compile the example I The generated Ada project files need two directories to compile a project obj and bin If your Ada IDE does not automatically create these directories you will need to create them outside the Ada IDE in both the top level directory and in the samples directory for the Count in 0 Sample Count loop Put_Line Writing HelloWorld count amp Count Img declare MSG DIDS Stieliag c DIDS tO _IDIDS_Sitieniag Hello World amp Counta imine amp 2 begin if Instance message DDS NULL_STRING then Finalize Instance message end if Instance message data Msg data end HelloWorld_Writer Write Instance_Data gt Instance Handle gt Instance_Handle Unchecked_Access delay Send_Period end loop if Instance message DDS NULL_STRING then Finalize Instance message end if 4 14 Compact Type Safe Data Programming with Data Types 4 3 2 2 Building the Generated Code You have now
47. apter on Configuring QoS with XML in the RTI Data Distribution Service User s Manual 3 On the publishing side send text strings as fast as possible prefixing each one with a serial number 4 On the subscribing side receive these strings keeping track of the highest num ber seen as well as other statistics Print these out periodically The steps for compiling and running the program are the same as mentioned in Build ing and Running Hello World Section 3 1 Run the publisher and subscriber from the NDDSHOME example lt language gt Hello_builtin directory using one of the QoS profile files provided in NDDSHOME example QoS by copying it into your current working directory with the file name USER_QOS_PROFILES xml You should see output like the following from the sub scribing application Understanding the Performance Results You will see several columns in the subscriber side output similar to Figure 6 1 L Seconds from start The number of seconds the subscribing application has been running It will print out one line per second J Total samples The number of data samples that the subscribing application has received since it started running L Total lost samples The number of samples that were lost in transit and could not be re paired since the subscribing application started running If you are using a QoS profile configured for strict reliability you can expect this column to always display 0 If
48. at the middleware will send on the network and many others The following is a short summary of just a few of the available policies Customizing Behavior QoS Configuration Reliability and Availability for Consistent Behavior with Critical Data J Reliability Specifies whether or not the middleware will deliver data reliably The reliability of a connection between a DataWriter and DataReader is entirely user configurable It can be done on a per DataWriter DataReader connection For some use cases such as the periodic update of sensor values to a GUI dis playing the value to a person best effort delivery is often good enough It is the fastest most efficient and least resource intensive CPU and network band width method of getting the newest latest value for a topic from DataWriters to DataReaders But there is no guarantee that the data sent will be received It may be lost due to a variety of factors including data loss by the physical transport such as wireless RF or Ethernet However there are data streams topics in which you want an absolute guaran tee that all data sent by a DataWriter is received reliably by DataReaders This means that the middleware must check whether or not data was received and repair any data that was lost by resending a copy of the data as many times as it takes for the DataReader to receive the data History Specifies how much data must be stored by the middleware for the DataWriter or Data
49. ate_Participant 0 Domain ID DDS DomainParticipantFactory PARTICIPANT _QOS_DEFAULT QoS null Listener DDS STATUS_MASK_NONE As you can see there are four pieces of information you supply when creating a new DomainParticipant L The ID of the domain to which it belongs I Its qualities of service QoS The discussion on Page 3 15 gives a brief introduc tion to the concept of QoS in DDS you will learn more in Chapter 4 Capabilities and Performance 1 Ada support requires a separate add on product Ada 2005 Language Support for RTI Data Distribution Service 3 14 Data Distribution Service DDS 101 LL Its listener and listener mask which indicate the events that will generate call backs to the DomainParticipant You will see a brief example of a listener callback when we discuss DataReaders below For a more comprehensive discussion of the DDS status and notification system see Chapter 4 in the User s Manual What is QoS Fine control over Quality of Service QoS is perhaps the most important feature of RTI Data Distribution Service Each data producer consumer pair can establish independent quality of service QoS agreements even in many to many topologies This allows DDS designs to support extremely complex and flexible data flow requirements QoS policies control virtually every aspect of the DDS model and the underlying communications mechanisms Many QoS policies are implemented as contr
50. b 7541 86W1n3 2V52005 Hel loPublisher ra Ready to write data When the subscriber is ready you can start writing Press CTRL C to terminate or enter an empty line to do a clean shutdown Hello World E x RTI ndds 4 4c examp e CPP Hel lo_simp e gt 0b7s4 1 86w n3 2VS2005 Hel loSubscriber T Ready to read data Press CTRL C to terminate Hello world fa Congratulations You ve run your first RTI Data Distribution Service program 3 2 Data Distribution Service DDS 101 RTI Data Distribution Service is network middleware for real time distributed applica tions It provides the communications service that programmers need to distribute time critical data between embedded and or enterprise devices or nodes RTI Data Distribu tion Service uses a publish subscribe communications model to make data distribution efficient and robust RTI Data Distribution Service implements the Data Centric Publish Subscribe DCPS API of the OMG s specification Data Distribution Service DDS for Real Time Systems DDS is the first standard developed for the needs of real time systems providing an efficient way to transfer data in a distributed system With RTI Data Distribution Service you begin your development with a fault tolerant and flexible communications infrastruc ture that will work over a wide variety of computer hardware operating systems lan 3 1 PHOM OIISH 3 2 1 Figure 3 1 3 12 gu
51. crosoft Visual Studio If this project came from an untrustworthy source it could cause damage to your computer or compromise your private information More Details Project load options Opens the project in Microsoft Visual Studio with increased security This option allows you to browse the contents of the project but some functionality such as IntelliSense is restricted When a project is loaded for browsing actions such as building cleaning publishing or opening designers could still remain unsafe O Load project normally Opens the project normally in Microsoft Visual Studio Use this option if you trust the source and understand the potential risks involved Microsoft visual Studio does not restrict any project Functionality and will not prompt you again For this project M Ask me for every project in this solution e On UNIX based systems The makefiles that RTI provides with the example code are intended to be used with the GNU distribution of the make util ity On modern Linux systems the make binary typically is GNU make On other systems GNU make is called gmake For the same of clarity the name gmake is used below Make sure that the GNU make binary is on your path before continuing Set Up the Environment on Your Deployment Machine Some configuration has to be done for the machine s on which you run your applica tion the RTI installer can t do that for you because those machines may or may not be the sam
52. d of time during which subscribing applications can repeatedly access them if they wish After that time has elapsed the middleware will automatically expire them from its internal cache This chapter describes Building and Running the Code Examples Section 5 1 and includes the following design patterns I Subscribing Only to Relevant Data Section 5 2 LI Accessing Historical Data when Joining the Network Section 5 3 LI Caching Data Within the Middleware Section 5 4 LI Receiving Notifications When Data Delivery Is Late Section 5 5 Next Chapter gt Chapter 6 Design Patterns for High Performance Building and Running the Code Examples Source code for the News example is located in the directory NDDSHOME example lt language gt News The example performs these steps 1 Parses the command line arguments 2 Loads the quality of service QoS file USER_QOS_PROFILES xml from the current working directory The middleware does this automatically you will not see code in the example to do this For more information on how to use QoS pro files see the chapter on Configuring QoS with XML in the RTI Data Distribution Service User s Manual 3 On the publishing side sends news articles periodically 4 On the subscribing side receives these articles and print them out periodically The steps for compiling and running the program are similar to those described in Building and Running Hello World Section 3 1
53. d the directory containing the DLLs to your Path environment variable If the Net framework is unable to load the dynamic libraries at run time it will throw a System I1O FileNotFoundException and your applica tion may fail to launch Step 2 Compile the Hello World Program The same example code is provided in C C C Java and Ada2 The following instructions cover C Java and Ada in detail the procedures for C and C are very similar The same source code can be built and run on different architecture The instructions also focus on Windows and UNIX based systems If you will be using an embedded platform see the Embedded Systems Addendum RTI_DDS_GettingStarted_EmbeddedSystemsAddendum pdf for more instructions especially for you C on Windows Systems To build the example applications 1 In the Windows Explorer go to NDDSHOME exam ple CPP Hello_simple win32 and open the Microsoft Visual Studio solution file for your architecture For example the file for Visual Studio 2005 for 32 bit platforms is Hello i86Win32VS2005 sIn 2 The Solution Configuration combo box in the toolbar indicates whether you are building debug or release executables select Release Select Build Solution from the Build menu 1 The file nddsdotnet dll or nddsdotnetd dll for debug must be in the executable directory Visual Stu dio will by default do this automatically 2 Ada support requires a separate add on product Ada 2005
54. defined your data type generated code for it and customized that code It s time to compile the example applications Building a Generated C C or Net Example on Windows Systems With the NDDSHOME environment variable set start Visual Studio and open the rtid dsgen generated workspace dsw or solution object sln file Select the Win32 Release configuration in the Build toolbar in Visual Studio or the Standard toolbar in Visual Studio NET From the Build menu select Build Solution This will build two projects lt IDL name gt _publisher and lt IDL name gt _subscriber Building a Generated Ada Example on a Linux System Ada support requires a separate add on product Ada 2005 Language Support for RTI Data Distribution Service Use the generated Ada project file to compile an example on any system Note The generated project file assumes the correct version of the compiler is already on your path NDDSHOME is set and NDDSHOME lib gnat is in your ADA_PROJECT_PATH gmake f makefile HelloWorld_ lt architecture gt After compiling the Ada example you will find the application executables in the direc tory samples bin The build command in the generated makefile uses the static release versions of the DDS libraries To select dynamic or debug versions of the libraries change the Ada compiler variables LIBRARY_TYPE and NDDS_BUILD in the build command in the makefile to build with the desired version of the libraries For exa
55. der participant Create_DataReader topic As_TopicDescription DDS Subscriber DATAREADER_QOS_ DEFAULT readerListener Unchecked_Access listener DDS STATUS_MASK ALL all callbacks if reader null then Put_Line Standard_Error Unable to create DataReader return end if end There are two listener related arguments to provide I Listener The listener object itself which must implement some subset of the call backs defined by the DataReaderListener supertype I Listener mask Which of the callbacks you d like to receive In most cases you will use one of the constants STATUS_MASK_ALL if you are providing a non null listener object of STATUS_MASK_NONE if you are not providing a lis tener There are some cases in which you might want to specify a different lis tener mask see the RTI Data Distribution Service User s Manual and online API documentation for more information Let s look at a very simple implementation of the on_requested_deadline_missed call back that prints the value of the key i e the news outlet name for the instance whose deadline was missed You can see this in the News example provided with C C and Java and Ada 1 Ada support requires a separate add on product Ada 2005 Language Support for RTI Data Distribution Service 5 24 Receiving Notifications When Data Delivery Is Late In C the code looks like this DDSDataReader reader const DDS
56. develop deploy and maintain distributed applications It has been proven in hundreds of unique designs for life and mission critical applications across a variety of industries RTI Data Distribution Service provides I Ultra low latency extremely high throughput messaging I Industry leading reliability and determinism I Connectivity for heterogeneous systems spanning thousands of applications RTI Data Distribution Service is flexible extensive quality of service QoS parameters adapt to your application assuring that you meet your real time reliability and resource usage requirements This chapter introduces basic concepts and summarizes how RTI Data Distribution Ser vice addresses your high performance needs After this introduction we ll jump right into building distributed systems The rest of this guide covers l First steps Installing RTI Data Distribution Service and creating your first simple application l Learning more An overview of the APIs and programming model with a special focus on the communication model data types and qualities of service J Towards real world applications An introduction to meeting common real world requirements If you d like to skip to the next chapter click Installing RTI Data Distribution Service 1 1 QWOIIOM L 1 1 Why Choose RTI Data Distribution Service RTI Data Distribution Service implements publish subscribe networking for high perfor mance distributed app
57. e as where you created and built the application a Make sure Java is available If you are a Java user see Step d in Section 3 1 1 1 for details Building and Running Hello World b Make sure the dynamic libraries are available Make sure that your application can load the RTI Data Distribution Service dynamic libraries If you use C C or Ada with static libraries the default configuration in the examples covered in this document you can skip this step However if you plan to use dynamic libraries or Java or Net which always use dynamic libraries you will need to modify your environment as described here To see if dynamic libraries are supported for your machine s architecture see the RTI Data Distribution Service Platform Notes For more information about where the Windows OS looks for dynamic libraries see http msdn microsoft com en us library ms682586 aspx e The dynamic libraries needed by C or C applications are in the directory NDDSHOME lib lt architecture gt The dynamic libraries needed by Ada applications are in the directory NDDSHOME lib GNAT gcc relocatable On UNIX based systems Add this directory to your LD_LIBRARY_PATH environment variable On Mac OS systems Add this directory to your DYLD_LIBRARY_PATH environment variable On Windows systems Add this directory to your Path environment variable or copy the DLLs inside into the directory containing your executable e The
58. e name of your target platform s Using our example path you will end up with opt rti ndds 4 5x Note If you have a license managed distribution of RTI Data Distribution Service the direc tory will be opt rti ndds 4 5x_lic 5 Optional If you want to use the TCP transport included with RTI Data Distribu tion Service in a secure configuration you also need to install RTI TLS Support and OpenSSL To purchase RTI TLS Support please contact your RTI account repre sentative 6 Read License Management Section 2 2 Installing on a Windows System Depending on your needs and license terms you may have an installer for RTI Data Dis tribution Service Professional Edition or a two or more zip archives a host archive con taining documentation header files and other files you need for development and one or more target archives containing the libraries and other files you need for deploy ment If you are using the RTI Data Distribution Service Professional Edition installer please see the RTI Data Distribution Service Professional Edition Getting Started Guide for details If you are installing RTI Data Distribution Service independently not part of RTI Profes sional Edition unpack the zip files as described below Depending on your version of Windows and where you want to expand these files your user account may or may not require administrator privileges 1 Create a directory for RTI Data Distribution Service We
59. e specified in configu ration files so that they can be tested and validated independently of the application logic When not specified the middleware will use default values chosen to provide good performance for a wide range of applications The result is simple to use networking that can expand and adapt to challenging appli cations both current and future RTI eliminates what is perhaps the greatest risk of com mercial middleware outgrowing the capability or flexibility of the design Connect Heterogeneous Systems RTI Data Distribution Service provides complete functionality and industry leading per formance for a wide variety of programming languages and platforms including T C C Net Java and Ada development platforms LJ Windows Linux Solaris AIX and other enterprise class systems LJ VxWorks INTEGRITY LynxOS and other real time and or embedded systems Applications written in different programming languages running on different hard ware under different operating systems can interoperate seamlessly over RTI Distribu tion Service RTI can connect disparate applications that must work together in even very complex systems Interoperate with Databases Event Engines and JMS Systems RTI provides connections between its middleware core and many types of enterprise software Simple but powerful integrations with databases Complex Event Processing CEP engines and other middlewares ensure that RTI can bind togethe
60. eak catch RETCODE_ ERROR e An error occurred e printStackTrace And in Ada if sample_info Valid_Data then Valid print it Ada Text_IO Put_Line DDS To_Standard_String ptr_sample end if Note that in this particular code example you will not find any reference to the Sub scriber class In fact as with Publishers creating the Subscriber object explicitly is optional because many applications do not have the need to customize any behavior at that level If you like this example choose not to create a Subscriber the middleware will implicitly choose an internal Subscriber object If you do want to create a Subscriber explicitly create it with a call to participant create_subscriber you can find more about this method in the online documentation and then simply replace the call to partici pant create_datareader with a call to subscriber create_datareader Topics Topics provide the basic connection points between DataWriters and DataReaders To communicate the Topic of a DataWriter on one node must match the Topic of a DataReader on any other node A Topic is comprised of a name and a type The name is a string that uniquely identifies the Topic within a domain The type is the structural definition of the data contained within the Topic this capability is described in Chapter 4 Capabilities and Performance 1 Ada support requires a separate add on product Ada 2005 Language Support for RTI Data
61. ed Systems cceccsesssessseeeees 2 7 2 4 2 Using the Command Line Tools on Windows Systems ccccsssesesesssssssesesens 2 8 2 4 3 Using Microsoft Visual Studio ccccccecesssssesesecneesesescsesesesescscseseececscsssnsneceesnes 2 8 Getting Started with RTI Data Distribution Service Building and Running Hello World ccc ccc cece ceeeeseececenenenesesesessneseseseeneneees 3 1 3 1 1 Step 1 Set Up the Environment 00 0 ccc ceeeeseeeeceseeseseenesesesesseeeeneeneeeeees 3 2 3 1 2 Step 2 Compile the Hello World Program cccceeesecesssseeeesesesssesesssctsesesescsens 3 6 3 1 3 Step 3 Start the Subseri b rre na En e 3 8 3 14 Step 4 Start the Publisher mutuei esa a lesedsseds dveaiistes teetathies 3 9 32 Data Distribution Service DDS 101 oe eeeseeecneeeeseeecsseecseecsceecscecseeecseeesseeesneeeneees 3 11 3 2 1 An Overview of DDS Objection e eiei 3 12 3 2 2 DomainParticipant ccccceceseeeeeeeecseeeeeececseseeseseecsenseesecssseeseeesseesseseesseneseeees 3 13 3 2 3 Publishers and DataWriter cccccccccessecsscessecesecessecessecsececssesseecsaeecsecsseeesaeeeseees 3 16 3 2 4 Subscribers and DataReaders cccccccccsccsscessecssscesseesssessecessecsseecsseeessesseeesaeceeees 3 18 S200 LOPICS EA EE A EEEE IAA att eves Sta sashalbant EA 3 21 3 26 Ke ysand Samples waite ians nan sania a inane aimed 3 23 4 Capabilities and Performance 4 1 Automatic Application DisCOVETY
62. ed to reinstall RTI Data Distribution Service However if you switch from a license managed distribution of RTI Data Distribution Service to one of the same version that does not require license management or visa versa RTI recommends that you first uninstall your original distribution before install ing your new distribution Doing so will prevent you from inadvertently using a mix ture of libraries from multiple installations Navigating the Directories Once you have installed RTI Data Distribution Service you can access the example code used in this document under NDDSHOME example RTI supports the C C C CLI C Java and Ada programming languages While we will examine the C Java and Ada examples in the following chapters you can access similar code in the lan guage of your choice The RTI Data Distribution Service directory tree is as follows NDDSHOME Root directory where RTI Data Distribution Service is installed class Java library files doc Documentation in HTML and PDF format example Example code ADA IC CPP CPPCLI CSHARP 1 Ada support requires a separate add on product Ada 2005 Language Support for RTI Data Distribution Service 2 5 UOHDI DISU Z 2 6 JAVA Q0S include jre lib gnat GNATgcc ReadMe html resource scripts Quality of Service QoS configuration files for the example code These configuration files do not depend on the language bindings
63. ence Infrastructure QoS Policies For Ada open doc html api_ada index html and select Infrastructure Module DDSQosTypesModule You can specify the QoS policies either in your application code or in one or more XML files Both mechanisms are functionally equivalent the News example uses the XML 1 Ada support requires a separate add on product Ada 2005 Language Support for RTI Data Distribution Service Subscribing Only to Relevant Data mechanism For more information see the chapter on Configuring QoS with XML in the RTI Data Distribution Service User s Manual To specify a time based filter in a QoS policy zl lt time_based_filter gt lt minimum_separation gt lt sec gt 1 lt sec gt lt nanosec gt 1 lt nanosec gt lt minimum_separation gt lt time_based_filter gt lt deadline gt lt period gt lt sec gt 3 lt sec gt lt nanosec gt 0 lt nanosec gt lt period gt lt deadline gt You can see this in the file USER_QOS_PROFILES xml provided with the C C Java and Ada News example uncomment it to specify a time based filter At the same time we implement a time based filter in the News example we increase the deadline period See the accompanying comment in the XML file as well as the online API documentation for more information about using the Deadline and Time BasedFilter QoS policies together 1 Ada support requires a separate add on product Ada 2005 Language Support
64. er return_loan articles articleInfos 5 18 Caching Data Within the Middleware And in Ada declare received_data aliased DDS KeyedString_Seq Sequence sample_info aliased DDS SampleInfo_Seq Sequence begin reader Read articles Access fill in data here articleInfos Access fill in parallel meta data here DDS LENGTH_UNLIMITED any articles received_data Access sample_info Access DDS LENGTH_UNLIMITED DDS ANY_SAMPLE STATE DDS ANY_VIEW_STATE DDS ANY_INSTANCE_ STATE Process data reader Return_Loan articles articleInfos for i in 1 DDS KeyedString_Seq Get_Length received_data Access loop printArticle DDS KeyedString_Seq Get received_data Access i DDS SampleInfo_Seq Get sample_info Access i end loop reader Return_Loan received_data Access sample_info Access exception when DDS NO_DATA gt null ignore this error nothing to read go back to sleep when DDS ERROR gt an error occurred stop reading raise end The read method takes several arguments L Data and Sampleinfo sequences The first two arguments to read or take are lists for the samples themselves and in parallel for meta data about those sam ples In most cases you will pass these collections into the middleware empty and the middleware will fill them for you The objects it places into these 1 Ada support requires a separate add on p
65. ers gt Self receiving FALSE exit end end loop The take_next_sample method retrieves a single data sample i e a message from the DataReader one at a time without blocking If it was able to retrieve a sample it will return DDS_RETCODE_OK If there was no data to take it will return DDS_RETCODE_NO_DATA Finally if it tried to take data but failed to do so because it encountered a problem it will return DDS_RETCODE_ERROR or another DDS_ReturnCode_t value see the online documentation for a full list of error codes RTI Data Distribution Service can publish not only actual data to a Topic but also meta data indicating for example that an object about which the DataReader has been receiv ing data no longer exists In the latter case the info argument to take_next_sample will have its valid_data flag set to false This simple example is interested only in data samples not meta data so it only pro cesses valid data if info valid_data Valid this isn t just a lifecycle sample print it cout lt lt ptr_sample lt lt endl 1 Ada support requires a separate add on product Ada 2005 Language Support for RTI Data Distribution Service Data Distribution Service DDS 101 3 2 5 Let s see the same thing in Java cry String sample stringReader take_next_sample info if info valid_data System out println sample catch RETCODE_NO_DATA noData No more data to read br
66. escription while Topic has a function As_TopicDescription that is useful to create a DataReader where a TopicDe scription is needed 1 Ada support requires a separate add on product Ada 2005 Language Support for RTI Data Distribution Service 5 6 Subscribing Only to Relevant Data 5 2 1 2 5 2 2 Running amp Verifying The following shows a simple filter with which the subscribing application indicates it is interested only in news articles from CNN you can specify such a filter with the f or filterExpression command line argument like this in the Java example gt run sh sub f key CNN OR key Reuters This example uses the built in KeyedString data type This type has two fields key a string field that is the type s only key field and value a second string This example uses the key field to store the news outlet name and the value field to store the article text The word key in the content filter expression key CNN refers to the field s name not the fact that it is a key field you can also filter on the value field if you like In your own data types you will use the name s of the fields you define For example out put see Figure 5 2 on page 5 8 You can find more detailed information in the online API documentation under Mod ules DDS API Reference Queries and Filters Syntax For Adal open doc html api_ada index html and look under DDS API Reference DDSQueryAndFilterSyntax
67. ever if the DataReader declares that it expects data twice a second and the DataWriter only promises to publish updates only once a second they will not be able to communicate Offered Deadlines A DataWriter promises to publish data at a certain rate by providing a finite value for the Deadline QoS policy either in source code or in one or more XML configuration files Both mechanisms are functionally equivalent the News example in C C Java and Ada uses XML files For more information about this mechanism see the chapter on Configuring QoS with XML in the RTI Data Distribution Service User s Manual The file USER_QOS_PROFILES xml in the News example for C C Java and Ada contains the following Deadline QoS policy configuration which applies to both DataWriters and DataReaders lt deadline gt lt period gt lt sec gt 2 lt sec gt lt nanosec gt 0 lt nanosec gt lt period gt lt deadline gt The DataWriter thus promises to publish at least one data sample of each instance every two seconds 1 Ada support requires a separate add on product Ada 2005 Language Support for RTI Data Distribution Service Receiving Notifications When Data Delivery Is Late 5 5 1 2 Java If a period of two seconds elapses from the time the DataWriter last sent a sample of a particular instance the writer s listener if one is installed will receive a callback to its on_offered_deadline_missed method
68. everely constrained High Throughput for Streaming Data 6 3 1 Figure 6 4 Implementation RTI can automatically flush batches based on the maximum number of samples the total batch size or elapsed time since the first sample was placed in the batch which ever comes first Your application can also flush the current batch manually Batching is completely transparent on the subscribing side no special configuration is necessary Batching Implementation Gein panen a RTI collects samples in a batch until the batch is flushed For more information on batching see the User s Manual Section 6 5 1 or online docu mentation the Batch QosPolicy is described in the Infrastructure Module Using the batching feature is simple just modify the QoS in the publishing applica tion s configuration file For example to enable batching with a batch size of 100 samples set the following QoS in your XML configuration file lt datawriter_qos gt lt batch gt lt enable gt true lt enable gt lt max_samples gt 100 lt max_samples gt lt batch gt lt datawriter_qos gt 6 1 SOUDWJOLeg YIH 10 SUI HOd UBIsEg 9 To enable batching with a maximum batch size of 8K bytes lt datawriter_qos gt lt batch gt lt enable gt true lt enable gt lt max_data_bytes gt 8192 lt max_data_bytes gt lt batch gt lt datawriter_qos gt To force the DataWriter to send whatever data is currently sto
69. ew different slices of your data at a time LJ You can view one instance at a time with read_instance take_instance read_next_instance and take_next_instance Ll You can view a single sample at a time with read_next_sample and take_next_sample For more information about these and other variations see the online API documenta tion open ReadMe html select a language and look under Modules Subscription Module DataReader Support FooDataReader For Ada open doc html api_ada index html and look under Subscription Module DDSReaderModule DDS Typed_DataReader_Generic Running amp Verifying To see the difference between read and take semantics replace read with take the arguments are the same rebuild the example and run again You will see that cached is never printed because every sample will be removed from the cache as soon as it is viewed for the first time Receiving Notifications When Data Delivery Is Late Many applications expect data to be sent and received periodically or quasi periodi cally They typically expect at least one data sample to arrive during each period a fail ure of data to arrive may or may not indicate a serious problem but is probably something about which the application would like to receive notifications For example L A vehicle may report its current position to its home base every second I Each sensor in a sensor network reports a new readi
70. f fers become full In reliable messaging the middleware keeps track of whether or not data sent has been received by subscribing applications and will resend data that was lost on transmission Like most reliable protocols including TCP the reliability protocol used by RTI uses additional packets on the network called metadata to know when user data packets are Reliable Messaging lost and need to be resent RTI offers the user a comprehensive set of tunable parameters that control how many and how often metadata packets are sent how much memory is used for internal buffers that help overcome intermittent data losses and how to detect and respond to a reliable subscriber that either falls behind or otherwise disconnects When users want applications to exchange messages reliably there is always a need to trade off between performance and memory requirements When strictly reliable com munication is enabled every written sample will be kept by RTI Data Distribution Service inside an internal buffer until all known reliable subscribers acknowledge receiving the sample If the publisher writes samples faster than subscribers can acknowledge receiving this internal buffer will eventually be completely filled exhausting all the available space in that case further writes by the publishing application will block Similarly on the subscriber side when a sample is received it is stored inside an internal receive buffer waiting f
71. for every domain in which the application will communicate Unless your applica tion is a bridging application it will typically participate in only one domain and have only one DomainParticipant A DDS DomainParticipant is analogous to a JMS Connection DomainParticipants are used to create Topics Publishers DataWriters Subscribers and DataReaders in the corresponding domain The following code shows how to instantiate a DomainParticipant You can find more information about all of the APIs in the online documentation To create a DomainParticipant in C participant DDSDomainParticipantFactory get_instance gt create_participant OF Domain ID DDS_PARTICIPANT OOS DEFAULT QoS NULL Listener DDS_STATUS_MASK_ NONE Here is the same logic in Java participant DomainParticipantFactory get_instance create_participant 0 Domain ID DomainParticipantFactory PARTICIPANT QOS_DEFAULT null Listener StatusKind STATUS_MASK_NONE 1 3 13 PHOM OIISH E Figure 3 2 Segregating Applications with Domains Node 1 App 1 Node 4 App 4 Pub Sub Domain0O Pub Sub Cmd Control Node 4 App 5 Node 2 App 2 Publish Subscribe Domain1 Status Node 3 App 3 Node 5 App 6 Subscribe Node 6 App 7 Node 7 App 8 Pub Sub Pub Sub In Adat the code to create a DomainParticipant looks like this participant Ada DDS DomainParticipantFactory Get_Instance Cre
72. get before it will block waiting for them to catch up In many systems consuming applications cannot acknowledge data as fast as its producing applications can put new data on the network In such cases the Resource Limits policy provides a throttling mechanism that governs how many sent but not yet acknowledged samples a DataWriter will maintain If a DataWriter is configured for reliable KEEP_ALL opera tion and it exceeds max_samples calls to write will block until the writer receives acknowledgements that will allow it to reclaim that memory If you see that your reliable publishing application is using an unacceptable amount of memory you can specify a finite value for max_samples By doing this you restrain the size of the DataWriter s cache causing it to use less memory however a smaller cache will fill more quickly potentially causing the writer to block for a time when sending decreasing throughput If decreased throughput proves to be an issue you can tune the reliability protocol to process acknowledgements and repairs more aggressively allow ing the writer to clear its cache more effectively A full discussion of the relevant reliabil ity protocol parameters is beyond the scope of this example However you can find a High Throughput for Streaming Data 6 3 useful example in high_throughput xml Also see the documentation for the DataRead erProtocol and DataWriterProtocol QoS policies in the on line API documentatio
73. h RTI Data Distribution Service Many readers will also want to look at additional documentation available online In particular RTI recommends the following LI RTI Public Knowledge Base Accessible from https support rtiicom The Knowledge Base provides sample code general information on RTI Data Distribu tion Service performance information troubleshooting tips and other technical details L RTI Customer Portal Accessible from https support rti com The portal pro vides a superset of the solutions available in the RTI Public Knowledge Base Select the Find Solution link to see sample code general information on RTI Data Distribution Service performance information troubleshooting tips and other technical details You must have a user name and password to access the portal these are included in the letter confirming your purchase If you do not have this letter please contact license rti com L RTI Example Performance Test available for C Java and NET This example application includes code and configuration files for testing and optimizing the performance of a simple RTI Data Distribution Service application on your system The program will test both throughput and latency under a wide variety of mid dleware configurations It also includes documentation on tuning the middleware and the underlying operating system The performance test can be downloaded from the RTI Knowledge Base accessi ble from https su
74. he middle ware are listed below Each time your RTI Data Distribution Service application starts it will look for the license file in the following locations until it finds a valid license 1 In your application s current working directory in a file called rti_license dat 2 In the location specified in the environment variable RTI_LICENSE_FILE which you may set to point to the full path of the license file including the filename for example C RTI my_license_file dat 3 In the RTI Data Distribution Service installation in the file NDDSHOME rti_license dat As RTI Data Distribution Service attempts to locate and read your license file you may depending on the terms of the license see a printed message with details about your license If the license file cannot be found or the license has expired your application may be unable to initialize RTI Data Distribution Service depending on the terms of the license If Navigating the Directories 2 2 2 2 3 that is the case your application s call to DomainParticipantFac tory create_participant will return null preventing communication If you have any problems with your license file please email support rti com Adding or Removing License Management If you are using an RTI software distribution that requires a license file and your license file changes for example you receive a new license for a longer term than your origi nal license you do not ne
75. he view state indicates whether the instance to which a sample belongs has been observed by a previous call to read or take By passing a view state mask to the DataReader you can indicate whether you re interested in all instances only those instances that you have never seen before NEW instances or only those instances that you have seen before NOT_NEW instances The most common value passed here is ANY_VIEW_STATE I Instance state The instance state indicates whether the instance to which a sam ple belongs is still alive ALIVE whether it has been disposed NOT_ALIVE_DISPOSED or whether the DataWriter has simply gone away or stopped writing it without disposing it NOT_ALIVE_NO_WRITERS The most common value passed here is ANY_INSTANCE_STATE For more infor mation about the DDS data lifecycle consult the RTI Data Distribution Service User s Manual and the online API documentation Unlike reading from a socket directly or calling receive in JMS a DDS read or take is non blocking the call returns immediately If no data was available to be read it will return in C and C or throw in Java and Net and Ada a NO_DATA result 1 Ada support requires a separate add on product Ada 2005 Language Support for RTI Data Distribution Service Receiving Notifications When Data Delivery Is Late 5 4 2 5 5 RTI Data Distribution Service also offers additional variations on the read and take methods to allow you to vi
76. hed by that DataWriter will be directed to that Topic As you will learn in the next chapter each Topic and therefore all DataWriters for that Topic is associated with a particular concrete data type The write operation which publishes data is type safe which means that before you can write data you must per form a type cast The code looks like this in C string_writer DDSStringDataWriter narrow data_writer In Java StringDataWriter dataWriter StringDataWriter participant create_datawriter ECGIOLG Publisher DATAWRITER_QOS_DEFAULT null listener StatusKind STATUS_MASK_NONI zal In Ada string_writer DDS Builtin_String_DataWriter Narrow data_writer Note that in this particular code example you will not find any reference to the Publisher class In fact creating the Publisher object explicitly is optional because many applica tions do not have the need to customize any behavior at that level If you choose not to create a Publisher the middleware will implicitly choose an internal Publisher object If you do want to create a Publisher explicitly create it with a call to partici pant create_publisher you can find more about this method in the online documenta tion and then simply replace the call to participant create_datawriter with a call to publisher create_datawriter 1 Ada support requires a separate add on product Ada 2005 Language Support for RTI Data Distrib
77. ibution Service alongside or connected to a web services infrastructure This format is described in Chapter 3 of the User s Manual e XML ina DDS specific format This XML format is terser and therefore easier to read and write by hand than an XSD file It offers the general benefits of XML extensibility and ease of integration while fully supporting DDS specific data types and concepts This format is described in Chapter 15 of the User s Manual LJ Define a dynamic type programmatically at run time This method may be appropriate for applications with dynamic data description needs applications for which types change frequently or cannot be known ahead of time It allows you to use an API similar to those of Tibco Rendezvous or JMS MapMessage to manipulate messages without sacrificing efficiency It is described in Running with Dynamic Types Section 4 3 3 The following sections of this document describe each of these models Using Built in Types RTI Data Distribution Service provides a set of standard types that are built into the mid dleware These types can be used immediately The supported built in types are String KeyedString Octets and KeyedOctets On the Java and Net platforms the latter two types are called Bytes and KeyedBytes respectively the names are different but the data is compatible across languages String and KeyedStrings can be used to send variable length strings of single byte characters Octets
78. ibution Service strongly typed data QoS based customization of behavior and industry leading performance These examples are described in Chapter 4 Capabilities and Performance and Chapter 6 Design Patterns for High Performance 1 Ada support requires a separate add on product Ada 2005 Language Support for RTI Data Distribution Service 2 Hello_dynamic is not provided for Ada Selecting a Development Environment L News This example demonstrates a subset of the rich functionality RTI Data Dis tribution Service offers including flexible support for historical and durable data built in data caching powerful filtering capabilities and tools for working with periodic data This example is described in Chapter 5 Design Patterns for Rapid Development 2 4 Selecting a Development Environment You can develop applications with RTI Data Distribution Service either by building and executing commands from a shell window or by using a development environment like Microsoft Visual Studio Eclipse or GPS from AdaCore 2 4 1 Using the Command Line Tools on UNIX based Systems For Java based applications you can use the following script files to build and execute L example JAVA lt example gt build sh Builds your Java source files no parame ters are needed L example JAVA lt example gt run sh Runs the main program in either Publisher or Subscriber mode It accepts the following parameters e pub sub Ru
79. ic As_TopicDescription DDS Subscriber DATAREADER_QOS_ DEFAULT QoS readerListener Unchecked_Access Listener DDS DATA_AVAILABLE STATUS RTI Data Distribution Service provides multiple ways for you to access your data you can receive it asynchronously in a listener you can block your own thread waiting for it to arrive using a helper object called a WaitSet or you can poll in a non blocking fash ion This example uses the former mechanism and you will see that it passes a non NULL listener to the create_datareader method The listener mask DATA_AVAILABLE_STATUS indicates that the application is only interested in receiving notifications of newly arriving data Let s look at the callback implementation in C retcode string_reader gt take_next_sample ptr_sample ONE if retcode DDS_RETCODE_NO_DATA No more samples break else if retcode DDS_RETCODE_OK cerr lt lt Unable to take data from data reader error lt lt retcode lt lt endl return 1 Ada support requires a separate add on product Ada 2005 Language Support for RTI Data Distribution Service 3 19 PHOM OIISH E 3 20 And in Ada loop begin data_reader Read_Next_Sample ptr_sample sample_info Access if sample_info Valid_Data then Ada Text_IO Put_Line DDS To_Standard_String ptr_sample end if exception when DDS NO_DATA gt No more samples exit when oth
80. ic release versions of the DDS libraries To select dynamic or debug versions of the libraries edit the makefile to change the library suf fixes Generally RTI Data Distribution Service uses the following convention for library suffixes z for static release zd for static debug none for dynamic release and d for dynamic debug For a complete list of the required libraries for each configuration see the RTI Data Distribution Service Platform Notes For example to change a C makefile from using static release to dynamic release libraries change this directive LIBS L NDDSHOME lib lt architecture gt Inddscppz lnddscz lnddscorez syslibs_ lt architecture gt to LIBS L NDDSHOME lib lt architecture gt Inddscpp lnddsc lnddscore syslibs_ lt architecture gt Running the Example Applications Run the example publishing and subscribing applications and see them communicate Running the Generated C Example First start the subscriber application HelloWorld_subscriber objs lt architecture gt HelloWorld_subscriber In this command window you should see that the subscriber wakes up every four sec onds to print a message HelloWorld subscriber sleeping for 4 sec HelloWorld subscriber sleeping for 4 sec HelloWorld subscriber sleeping for 4 sec Compact Type Safe Data Programming with Data Types 4 3 2 3 2 Java Next open another command prompt window and start the publisher a
81. ility gt lt datawriter_qos gt lt datareader_qos gt lt reliability gt lt kind gt RELIABLE_ RELIABILITY _QOS lt kind gt lt reliability gt lt datareader_qos gt This section of the QoS file enables reliability on the DataReader and DataWriter and tells the middleware that a call to write may block up to 5 seconds if the DataWriter s cache is full of unacknowledged samples If no space opens up in 5 seconds write will Reliable Messaging 6 2 1 2 return with a timeout indicating that the write operation failed and that the data was not sent Set History To KEEP_ALL The History QoS determines the behavior of a DataWriter or DataReader when its inter nal buffer fills up There are two kinds L KEEP_ALL The middleware will attempt to keep all the samples until they are acknowledged when the DataWriter s History is KEEP_ALL or taken by the application when the DataReader s History is KEEP_ALL L KEEP_LAST The middleware will discard the oldest samples to make room for new samples When the DataWriter s History is KEEP_LAST samples are dis carded when a new call to write is performed When the DataReader s History is KEEP_LAST samples in the receive buffer are discarded when new samples are received This kind of history is associated with a depth that indicates how many historical samples to retain lt datawriter_qos gt lt history gt lt kind gt KEEP_ALL_ HIST
82. imal latency e Clear semantics for managing multiple sources of the same data e Customizable Quality of Service and error notification e Guaranteed periodic messages with minimum and maximum rates set by subscriptions e Notifications when applications fail to meet their deadlines e Synchronous or asynchronous message delivery to give applications con trol over the degree of concurrency e Ability to send the same message to multiple subscribers efficiently including support for reliable multicast with customizable levels of posi tive and negative message acknowledgement Reliable messaging Enables subscribing applications to customize the degree of reliability required Reliability can be tuned you can guarantee delivery no matter how many retries are needed or try messages only once for fast and deter ministic performance You can also specify any settings in between No other middleware lets you make this critical trade off on a per message stream basis Multiple communication networks Multiple independent communication net works domains each using RTI Data Distribution Service can be used over the same physical network to isolate unrelated systems or subsystems Individual applications can participate in one or multiple domains Symmetric architecture Makes your application robust No central server or privileged nodes means your system is robust to application and or node fail ures Dynamic Topics subscriptio
83. ime Now suppose that an application sends a 64 KB datagram The likelihood that all fragments will arrive at their destination is 97 to the 64th power or less than 15 6 15 SOUDWJOLed YIH 10 SUI HOd UBIsEg 9 6 16 an unreliable protocol like UDP such losses will eventually lead to near total data loss as data size increases Over a protocol like TCP which provides reliability at the level of whole IP datagrams not fragments mounting losses will eventually lead to the net work filling up with repairs which will themselves be lost the result can once again be near total data loss To solve this problem you need to repair data at the granularity at which it was lost you need not message level reliability but fragment level reliability This is an impor tant feature of RTI Data Distribution Service When sending packets larger than the MTU of your underlying link use RTI s data fragmentation and asynchronous publishing fea tures to perform the fragmentation at the DDS level hence relieving the IP layer of that responsibility lt datawriter_qos gt lt publish_mode gt lt kind gt ASYNCHRONOUS_PUBLISH_MODE_QOS lt kind gt lt flow_controller_name gt DDS_DEFAULT_FLOW_CONTROLLER_NAME lt flow_controller_name gt lt publish_mode gt lt datawriter_qos gt lt participant_qos gt lt property gt lt value gt lt element gt lt name gt dds transport UDPv4 builtin parent message_size max lt name g
84. in the middleware is referred to as durability You only need to indicate the degree of durability in which you re inter ested I Volatile Data is relevant to current subscribers only Once it has been acknowl edged if reliable communication has been turned on it can be removed from the service This level of durability is the default if you specify nothing you will get this behavior I Transient local Data that has been sent may be relevant to late joining subscrib ers subject to any history depth lifespan and content and or time based filters 5 14 Accessing Historical Data when Joining the Network 5 3 1 defined Historical data will be cached with the DataWriter that originally pro duced it Once that writer has been shut down for any reason intentionally or unintentionally however the data will no longer be available This lightweight level of durability is appropriate for non critical data streams without stringent data availability requirements I Transient Data that has been sent may be relevant to late joining subscribers and will be stored externally to the DataWriter that produced that data This level of durability requires one or more instances of the RTI Persistence Service on your network As long as one or more of these persistence service instances is func tional the durable data will continue to be available even if the original DataW riter shuts down or fails However if all instances of the
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86. ive throughput as a percentage of the theo retical capacity of the link increases as the amount of data in each network packet increases To put this relationship in another way when transmitting a packet is expen sive it s advantageous to put as much data into it as possible However the trend reverses itself when the packet size becomes larger than the maximum transmission unit MTU of the physical network Figure 6 7 Example Throughput Results over VSat Connection A in gt 5 C g ao gt co 100 10000 Data Length bytes Correlation between sample size and bandwidth usage for a satellite connection with 3 packet loss ratio To understand why this occurs remember that data is sent and received at the granular ity of application samples but dropped at the level of transport packets For example an IP datagram 10 KB in size must be fragmented into seven 1500 byte Ethernet frames and then reassembled on the receiving end the loss of any one of these frames will make reassembly impossible leading to an effective loss not of 1500 bytes but of over 10 thousand bytes On an enterprise class network or even over the Internet loss rates are very low and therefore these losses are manageable However when loss rates reach several percent the risk of losing at least one fragment in a large IP datagram becomes very large Over 1 Suppose that a physical network delivers a 1 KB frame successfully 97 of the t
87. l system failure when data is not received in time For topics on which data is not expected to be peri odic the deadline period should be set to an infinite value You can specify an object s QoS two ways a programmatically in your application s source code or b in an XML configuration file The same parameters are available regardless of which way you choose For complete information about all of the policies available see Chapter 4 in the RTI Data Distribution Service User s Manual or see the online documentation The examples covered in this document are intended to be configured with XML files You can find several example configurations called profiles in the directory NDDSHOME example QoS The easiest way to use one of these profile files is to either set the environment variable NDDS_QOS_PROFILES to the path of the file you want or copy that file into your current working directory with the file name USER_QOS_PROFILES xml before running your application Compact Type Safe Data Programming with Data Types How data is stored or laid out in memory can vary from language to language compiler to compiler operating system to operating system and processor to processor This combination of language compiler operating system processor is called a platform Any modern middleware must be able to take data from one specific platform say C gcc 3 2 2 Solaris Sparc and transparently deliver it to another for example Java JDK
88. les that will be used in the generated example project file Building and Running Hello World Make sure the Ada compiler gprbuild is in your path The makefile used by the example assumes that gprbuild is in your path On UNIX based systems Add the path to gprbuild to your PATH environment variable Make sure Java is available If you plan to develop in a language other than Java you do not need Java installed on your system and can safely skip this step If you will be going through the examples in Java ensure that appropriate java and javac executables are on your path They can be found within the bin direc tory of your JDK installation The Release Notes list the Java versions that are sup ported On Linux systems Note that GNU java from the GNU Classpath project is not supported and will typically not work but is on the path by default on many Linux systems Make sure the preprocessor is available Check whether the C preprocessor e g cpp is in your search path This step is optional but makes code generation with the rtiddsgen utility more convenient Chapter 4 Capabilities and Performance describes how to use rtiddsgen On Windows systems e If you have Microsoft Visual Studio installed Running the script vevars32 bat vsvars32 bat or vevarsall bat depending on your version of Visual Studio will update the path for a given command prompt If the Visual Studio installer did not add cl to
89. lications It complies with the Data Distribution Service DDS standard from the Object Management Group OMG Developers familiar with JMS and other middleware will see similarities but will also find that DDS is not just another MOM message oriented middleware standard Its unique peer to peer architecture and unprecedented flexibility delivers much higher performance and adaptation to challenging applications DDS is the first truly real time networking technology stan dard RTI Data Distribution Service is by far the market leading implementation of DDS Reduce Risk Through Performance and Availability RTI Data Distribution Service provides top performance whether measured in terms of latency throughput or real time determinism One reason is its elegant peer to peer architecture Traditional messaging middleware requires dedicated servers to broker messages introducing throughput and latency bottlenecks and timing variations Brokers also increase system administration costs and represent single points of failure within a dis tributed application putting data reliability and availability at risk RTI doesn t use brokers Messages flow directly from publishers to subscribers with minimal overhead All the functions of the broker including discovery finding data sources and sinks routing directing data flow and naming identifying data types and topics are handled in a fully distributed reliable fashion behind the scenes
90. lling for it For more information about the different ways to read data select Modules Programming How To s DataReader Use Cases in the online API documentation In this case periodic polling makes the behavior easy to illustrate Along with each article it prints it includes the time at which that article was published and whether that article has been read before or whether it was cached from a previous read By default both the publishing and subscribing applications run for 20 seconds and then quit To run them for a different number of seconds use the r command line argument Figure 5 1 shows example output using the default run time and a domain ID of 13 set with the command line option d 13 Subscribing Only to Relevant Data From reading Chapter 3 you already understand how to subscribe only to the topics in which you re interested However depending on your application you may be inter 1 Ada support requires a separate add on product Ada 2005 Language Support for RTI Data Distribution Service 5 3 juowidojeasg pidpy 10 SUJ HOd UBISeq S Figure 5 1 Example Output for Both Applications Terminal ssh 60x45 gt run sh pub d 13 f gt run sh sub d 13 a News Example Application News Example Application Copyright 20089 Real Time Innovations Inc Copyright 2009 Real Time Innovations Inc Articles published in Last period as of 9 50 15 AM Available articles as of 9 50 14 AM Fr
91. ltin Hello_idl and Hello_dynamic provide the same functionality but use different data types in order to help you understand the different type definition mechanisms offered by RTI Data Distribution Service and their tradeoffs They implement a simple through put test the publisher sends a payload to the subscriber which periodically prints out some basic statistics You can use this simple test to quickly see the effects of your sys tem design choices programming language target machines QoS configurations and so on The QoS parameters do not depend on the language used for your application and sel dom on the operating system there are few key exceptions so you should be able to use the XML files with the example in the language of your choice This chapter describes I Building and Running the Code Examples LI Reliable Messaging LJ High Throughput for Streaming Data E Streaming Data over Unreliable Network Connections 1 Dynamic types are not supported when using Ada 2005 Language Support for RTI Data Distribution Ser vice 6 1 SOUDWWIOLeg YIH 10 SUI HOd uBIseg 9 6 1 Figure 6 1 Building and Running the Code Examples Example Output from the Subscribing Application in C C C or Java 0 0OO Terminal ssh 75x25 gt 0bjs i86Linux2 6gcc3 4 3 Hello sub domain 13 Hello Example Application Copyright 2088 Real Time Innovations Inc Sec from Total Total Lost Curr Lost Average
92. m Reuters 10 02 47 AM From Reuters 10 02 47 AM From Reuters 10 02 47 AM From CNN 10 02 48 AM From Reuters 10 02 47 AM From ONN 10 02 47 AM From ONN 10 02 48 AM From Reuters 10 02 48 AM From Reuters 10 02 48 AM From CNN 10 02 48 AM From Reuters 10 02 48 AM From Reuters 10 02 49 AM From Reuters 10 02 49 AM From ON 10 02 49 AM From Reuters 10 02 49 AM From Reuters 10 02 49 AM From Reuters 10 02 49 AM From OWN 10 02 49 AM From Reuters 10 02 50 AM From Reuters Available articles os of 10 02 10 02 47 AM From CNN 10 02 47 AM From CNN 10 02 48 AM From CNN 10 02 49 AM From CNN 10 02 49 AM From ONN 10 02 50 AM From Reuters 10 02 50 AM From OW 10 02 50 AM From Reuters 10 02 50 AM From Reuters lorem ipsum 5 Available orticles os of 10 02 se AM Lorem ipsum 1 cached lt CNN articles still available lorem ipsum 2 coached lorem ipsum 6 lores ipsus 7 lorem ipsum 3 lorem ipsus 8 loren ipsum 9 lorem ipsus 10 lorea ipsus 4 lt lorem ipsus 11 lorem ipsum 12 lorem ipsum 13 lorem ipsum 5 lorem ipsum 14 lorem ipsum 15 s2 AM loren ipsum 1 cached Lorem ipsum 2 cached lorem ipsum 3 cached lorem ipsum 4 cached Lorem ipsum 5 cached lorem ipsum 16 Lorem ipsum 6 lorem ipsum 17 l
93. mance provides specific QoS configuration examples to help you get started You can quickly see the effects of the changes you make using the code examples described in that chapter You can benchmark the performance of RTI Data Distribution Service on your own systems with the RTI Example Perfor mance Test You can download the test from the RTI Public Knowledge Base 4 1 SOUDUWIO ed PUD s yi qodo vy 4 1 4 2 http www rti com kb Search for Example Performance Test for RTI Data Distribution Service For more information about this test see Chapter 7 LJ You can also review the data from several performance benchmarks here http www tti com products dds benchmarks cpp linux html Next Chapter gt Chapter 5 Design Patterns for Rapid Development Automatic Application Discovery As you ve been running the code example described in this guide you may have noticed that you have not had to start any server processes or configure any network addresses Its built in automatic discovery capability is one important way in which RTI Data Distribution Service differs from other networking middleware implementations It is designed to be low overhead and require minimal configuration so in many cases there is nothing you need to do it will just work Nevertheless it s helpful to under stand the basics so that you can decide if and when a custom configuration is necessary Before applications can communicate
94. mpact Type Safe Data Programming with Data Types 4 3 3 Look back in the first subscribing command window You should see that the sub scriber is now receiving messages from the publisher HelloWorld subscriber sleeping for 4 sec msg Hello World 0 HelloWorld subscriber sleeping for 4 sec msg Hello World 1 HelloWorld subscriber sleeping for 4 sec msg Hello World 2 Running with Dynamic Types Note Dynamic types are not supported when using Ada 2005 Language Support for RTI Data Distribution Service This method may be appropriate for applications for which the structure type of mes sages changes frequently or for deployed systems in which newer versions of applica tions need to interoperate with existing applications that cannot be recompiled to incorporate message type changes As your system evolves you may find that your data types need to change And unless your system is relatively small you may not be able to bring it all down at once in order to modify them Instead you may need to upgrade your types one component at a time or even on the fly without bringing any part of the system down While covering dynamic types is outside the scope of this chapter you can learn more about the subject in Chapter 3 of the RTI Data Distribution Service User s Manual You can also view and run the Hello World example code located in NDDSHOME example lt language gt Hello_dynamic src 4
95. mple if the application must be compiled with the relocatable debug version of the libraries compile with the following command gprbuild p P samples helloworld samples gpr XOS Linux XLIBRARY_TYPE relocatable XNDDS_BUILD debug XARCH S ARCH 1 There is one exception For C users Select the Mixed Platforms Release configuration in the Standard toolbar in Visual Studio NET 2005 Select Build Solution from the Build menu This will build 3 proj ects lt IDL name gt _type lt IDL name gt _publisher and lt IDL name gt _subscriber Note for Visual Studio 2008 users Although the project files generated by rtiddsgen are for Visual Studio 2005 you can open them with Visual Studio 2008 Visual 2008 will launch an upgrade wizard to convert the files to Visual Studio 2008 project files Once the upgrade is done the rest of the steps are the same 4 15 SOUDUWO ed PUD s yi qodo vy 4 3 2 2 3 Java 4 3 2 3 4 3 2 3 1 4 16 Building a Generated Example on Other Platforms Use the generated makefile to compile a C or C example on a UNIX based system or a Java example on any system Note the generated makefile assumes the correct version of the compiler is already on your path and that NDDSHOME is set After compiling gmake f makefile HelloWorld_ lt architecture gt the C or C example you will find the application executables in a directory objs lt architecture gt The generated makefile includes the stat
96. n High Throughput for Streaming Data This design pattern is useful for systems that produce a large number of small messages at a high rate In such cases there is a small but measurable overhead in sending and in the case of reliable communication acknowledging each message separately on the network It is more efficient for the system to manage many samples together as a group referred to in the API as a batch and then send the entire group in a single network packet This allows RTI Data Distribution Service to minimize the overhead of building a datagram and traversing the network stack Batching increases throughput when writing small samples at a high rate As seen in Figure 6 2 throughput can be increased several fold much more closely approaching the physical limitations of the underlying network transport Figure 6 2 Benefits of Batching Mbit sec Max Throughput Mbps B Withoutbatching E 1Okbatches oo x 6t 128 25 512 14 me 4096 8192 Message Size bytes Batching delivers tremendous benefits for messages of small size 6 9 SOUDWIOPed YIH 10 SU1 4Od UBISeg 9 Figure 6 3 Benefits of Batching Sample Rates 6 10 1 500 000 1 250 000 1 000 000 750 000 500 000 Samples Per Second 250 000 0 200 400 600 800 1 000 Sample Size bytes A subset of the batched throughput data above expressed in terms of samples per second Collecting samples into a batch implies that the
97. n as publisher or subscriber e verbose lIncreases output verbosity This script accepts other options which we will discuss in later chapters For C and C applications for UNIX based systems you can use the make command with this makefile L example C CPP lt example gt make Makefile lt architecture gt where lt architecture gt reflects the compiler OS and processor combination for your development environment If you do not see your architecture listed see Generating Code with rtiddsgen Section 4 3 2 1 for instructions on how to gen erate an example makefile For Ada applications use the make command with this makefile Ll example ADA lt example gt make Makefile lt architecture gt 1 Ada support requires a separate add on product Ada 2005 Language Support for RTI Data Distribution Service 2 7 UOHDI D SU Z 2 4 2 2 4 3 2 8 where lt architecture gt reflects the compiler OS and processor combination for your development environment If you do not see your architecture listed see Generating Code with rtiddsgen Section 4 3 2 1 for instructions on how to gen erate an example makefile Using the Command Line Tools on Windows Systems For Java based applications you can use the following script files to build and execute I example JAVA lt example gt build cmd Builds Java source files no parame ters are needed I example JAVA lt example gt run cmd Runs the main prog
98. native dynamic libraries needed by Java applications are in the directory NDDSHOME lib lt architecture gt Your architecture name ends in jdk e g i86Linux2 6gcc3 4 3jdk The gcc part only present on UNIX based architec tures identifies the corresponding native architecture that relies on the same version of the C runtime library The native dynamic libraries needed by Ada applications are in the directory NDDSHOME lib lt architecture gt The gcc part of lt architecture gt identifies the corresponding native architecture that relies on the same version of the C run time library On UNIX based systems Add this directory to your LD_LIBRARY_PATH environment variable On Mac OS systems Add this directory to your DYLD_LIBRARY_PATH environment variable On Windows systems Add this directory to your Path environment variable 1 Ada support requires a separate add on product Ada 2005 Language Support for RTI Data Distribution Service 2 In the Platform Notes see the Building Instructions table for your target architecture 3 5 PHOM OIISH E 3 6 e Java jar files are in the directory NDDSHOME class They will need to be on your application s class path e On Windows systems The dynamic libraries needed by Net applications are in the directory 7 NDDSHOME lib i86Win32dotnet2 0 You will need to either copy the DLLs from that directory to the directory containing your exe cutable or ad
99. nd unique benefits of RTI Data Distribution Service I A rich set of functionality implemented for you by the middleware so that you don t have to build it into your application Most of this functionality including sophisticated data filtering and expiration support for durable historical data and built in support for periodic data and deadline enforcement can be defined partially or even completely in declarative quality of service QoS poli cies specified in an XML file allowing you to examine and update your applica tion s configuration without rebuilding or redeploying it See Customizing Behavior QoS Configuration Section 4 2 for more information about how to configure QoS policies Chapter 5 Design Patterns for Rapid Development describes how to reduce filter and cache data as well as other common func tional design patterns L Compact type safe data The unique and expressive data typing system built into RTI Data Distribution Service supports not only opaque payloads but also highly structured data It provides both static and dynamic type safety without the network overhead of the self describing messages of other networking middleware implementations See Compact Type Safe Data Programming with Data Types Section 4 3 for more information J Industry leading performance RTI Data Distribution Service provides industry leading latency throughput and jitter performance Chapter 6 Design Patterns for High Perfor
100. ng every 0 5 seconds I A radar reports the position of each object that it s tracking every 0 2 seconds If any vehicle any sensor or any radar track fails to yield an update within its promised period another part of the system or perhaps its human operator may need to take a corrective action 1 Ada support requires a separate add on product Ada 2005 Language Support for RTI Data Distribution Service 5 2 juowidojeasg pidpy 10 SUJ HOd UBISseq S 5 5 1 5 5 1 1 5 22 In addition to built in deadline support RTI Data Distribution Service has other features useful to applications that publish and or receive data periodically For example it s possible to down sample high rate periodic data see Subscribing Only to Relevant Data Section 5 2 Implementation Deadline enforcement is comprised of two parts 1 QoS policies that specify the dead line contracts and 2 listener callbacks that are notified if those contracts are violated Deadlines are enforced independently for DataWriters and DataReaders However the Deadline QoS policy like some other policies has request offer semantics the DataWriter must offer a level of service that is the same or better than the level of service the DataReader requests For example if a DataWriter promises to publish data at least once every second it will be able to communicate with a DataReader that expects to receive data at least once every two seconds How
101. ns and publications can be added or removed from the system at any time QWODIOM L L Multiple network transports RTI Data Distribution Service includes support for UDP IP IPv4 and IPv6 including for example Ethernet wireless and Infini band networks and shared memory transports It also includes the ability to dynamically plug in additional network transports and route messages over them It can be configured to operate over a variety of transport mechanisms including backplanes switched fabrics and other networking technologies Multi platform and heterogeneous system support Applications based on RTI Data Distribution Service can communicate transparently with each other regard less of the underlying operating system or hardware Consult the Release Notes to see which platforms are supported in this release Vendor neutrality and standards compliance The RTI Data Distribution Service API complies with the DDS specification On the network it supports the open DDS Interoperability Protocol Real Time Publish Subscribe RTPS which is also an open standard from the OMG What Can RTI Data Distribution Service Do Am I Better Off Building My Own Middleware Sometimes application projects start with minimal networking needs So it s natural to consider whether building a simplified middleware in house is a better alternative to purchasing a more complex commercial middleware While doing a complete Return on
102. o decrease the per sample overhead Be careful not to set your batch size larger than your link s MTU see Managing Your Sample Size Section 6 4 1 1 For more information on how to configure throughput for small samples see High Throughput for Streaming Data Section 6 3 6 19 SOUDWJOLEd YIH 10 SUI HOd UBIseg 9 6 20 Chapter 7 The Next Steps Congratulations You have completed the Getting Started Guide This document is of course only an introduction to the power and flexibility of RTI Data Distribution Service We invite you to explore further by referring to the wealth of information examples and resources available The RTI Data Distribution Service documentation includes Ll Getting Started Guide RTI_DDS_GettingStarted pdf This document describes how to install RTI Data Distribution Service It also lays out the core value and con cepts behind the product and takes you step by step through the creation of a sim ple example application Developers should read this document first If you are using RTI Data Distribution Service on an embedded platform or with a database you will find additional documents that specifically address these con figurations e Addendum for Embedded Systems RTI_DDS_GettingStarted_EmbeddedSystemsAddendum pdf e Addendum for Database Setup RTI_DDS_GettingStarted_DatabaseAddendum pdpf L Whats New RTI_LDDS_WhatsNew pdf This document describes changes and enhancements in
103. om Reuters Lorem ipsum 1 9 50 13 AM From Reuters Lorem ipsum 1 From AP Lorem ipsum 1 9 50 13 AM From AP Lorem ipsum 1 From CNN Lorem ipsum 1 9 50 13 AM From CNN Lorem ipsum 1 From Bloomberg Lorem ipsum 1 9 50 13 AM From Bloomberg Lorem ipsum 1 From NY Times Lorem ipsum 1 9 13 AM From NY Times Lorem ipsum 1 SSSSSSSSESS From Economist Lorem ipsum 1 9 AM From Economist Lorem ipsum 1 From Reuters Lorem ipsum 2 9 50 13 AM From Reuters Lorem ipsum 2 From Reuters Lorem ipsum 3 9 50 14 AM From Reuters Lorem ipsum 3 From AP Lorem ipsum 2 9 50 14 AM From AP Lorem ipsum 2 From Reuters Lorem ipsum 4 9 50 14 AM From Reuters Lorem ipsum 4 From CNN Lorem ipsum 2 9 50 14 AM From CNN Lorem ipsum 2 From Reuters Lorem ipsum 5 Available articles as of 9 5 16 AM From AP Lorem ipsum 3 9 50 13 AM From AP Lorem ipsum 1 cached From Bloomberg Lorem ipsum 2 9 50 13 AM From CNN Lorem ipsum 1 cached From Reuters Lorem ipsum 6 9 50 13 AM From Bloomberg Lorem ipsum 1 cached From NY Times Lorem ipsum 2 9 50 13 AM From NY Times Lorem ipsum 1 cached From Reuters Lorem ipsum 7 9 50 13 AM From Economist Lorem ipsum 1 cached From AP Lorem ipsum 4 9 50 14 AM From AP Lorem i
104. or the application to take the data for processing If the subscribing application doesn t take the received samples fast enough the internal receive buffer may fill up in that case newly received data will be discarded and would need to be repaired by the reliable protocol Although the size of those buffers can be controlled from the QoS you can also use QoS to control what RTI Data Distribution Service will do when the space available in one of those buffers is exhausted There are two possible scenarios for both the publisher and subscriber Publishing side If write is called and there is no more room in the DataWriter s buffer RTI Data Distribution Service can 1 Temporarily block the write operation until there is room on this buffer for example when one or more samples is acknowledged to have been received from all the subscribers 2 Drop the oldest sample from the queue to make room for the new one Subscribing side If a sample is received from a publisher and there is no more room on the DataReader s buffer 1 Drop the sample as if it was never received The subscribing application will send a negative acknowledgement requesting that the sample be resent 2 Drop the oldest sample from the queue to make room for the new one 1 RTI Data Distribution Service also supports reliability based only on negative acknowledgements NACK only reliability This feature is described in detail in the User s Manual
105. orem ipsum 18 lorem ipsum 19 lorem ipsun 7 lorem ipsum 20 lorem ipsun 21 Lorem ipsum 22 lorem ipsum 8 lorem ipsum 23 lorem ipsum 24 Lorem ipsum 25 lorem ipsus 9 Lorem ipsum 3 cached 4 CNN articles 1 amp 2 expired lorem ipsum 4 cached due to lifespan 6 seconds Lorem ipsum 5 cached Lorem ipsum 6 cached 10 02 50 AM From Reuters 10 02 50 AM From ONN 10 02 51 AM From Reuters 10 02 51 AM From Reuters 10 02 51 AM From Reuters 10 02 51 AM From ONN 10 02 51 AM From Reuters 10 02 51 AM From Reuters 10 02 52 AM From Reuters 10 02 52 AM From ONN articles as of 10 02 s4 AM 10 02 48 AM From ONN 10 02 49 AM From ONN 10 02 49 AM From ONN 10 02 50 AM From ONN 10 02 50 AM From CNN Lorem ipsum 7 cached lores ipsum 1 _ Article 1 initially received lorem ipsum 1 lorem ipsum 2 gt lorem ipsum 3 lorem ipsum 4 lorem ipsum 2 from Reuters and CNN Reuters articles 1 5 expired due to history depth 10 samples 5 11 5 2 3 5 2 3 1 5 12 Try changing the history depth and lifespan duration in the file USER_QOS_PROFILES xml to see how the example s output changes Time Based Filtering A time based filter allows you to specify a minimum separation between the data samples your subscribing application receives If da
106. over ime The diff lues of the Topi db M eee se ee time e different values of the Topic passed between appli analogous to a message in cations are called samples other publish subscribe An application may use a single Topic to carry data about Middleware many objects For example a stock trading application may have a single topic Stock Price that it uses to communicate information about Apple Google Microsoft and many other companies Similarly a radar track management application may have a single topic Aircraft Position that carries data about many different airplanes and other vehicles These objects within a Topic are called instances For a specific data type you can select one or more fields within the data type to forma key A key is used to uniquely identify one instance of a Topic from another instance of the same Topic very much like how the primary key in a database table identifies one record or another Samples of different instances have different values for the key Sam ples of same instance of a Topic have the same key Note that not all Topics have keys For Topics without keys there is only a single instance of that Topic 3 23 PHOM OII H 3 24 Chapter 4 Capabilities and Performance In the previous chapter you learned the basic concepts in RTI Data Distribution Service and applied them to a simple Hello World application In this chapter you will learn more about some of the powerful a
107. pplication HelloWorld_publisher For example objs lt architecture gt HelloWorld_publisher In this second publishing command window you should see Writing HelloWorld count 0 Writing HelloWorld count 1 Writing HelloWorld count 2 Look back in the first subscribing command window You should see that the sub scriber is now receiving messages from the publisher HelloWorld subscriber sleeping for 4 sec msgs COM VW oraslecllme OS HelloWorld subscriber sleeping for 4 sec msg Hello World 1 HelloWorld subscriber sleeping for 4 sec msg Hello World 2 Running the Generated Java Example You can run the generated applications using the generated makefile On most plat forms the generated makefile assumes the correct version of java is already on your path and that the NDDSHOME environment variable is set First run the subscriber gmake f makefile _HelloWorld_ lt architecture gt HelloWorldSubscriber In this command window you should see that the subscriber wakes up every four sec onds to print a message HelloWorld subscriber sleeping for 4 sec HelloWorld subscriber sleeping for 4 sec HelloWorld subscriber sleeping for 4 sec Next run the publisher gmake f makefile HelloWorld_ lt architecture gt HelloWorldPublisher 1 One exception in LynxOS see the chapter Getting Started on Embedded UNIX like Systems in the Getting Started Guide Addendum for Embedded Platforms SO
108. pport rti com In the Performance category look for Example Performance Test for RTI Data Distribution Service You can also review the data from several performance benchmarks here http www rti com products dds benchmarks cpp linux html L Whitepapers and other articles These documents are available from http www rti com resources Of course RTI also offers excellent technical support and professional services To con tact technical support simply log into the portal send email to support rti com or con tact the telephone number provided for your region We thank you for your consideration and wish you success in meeting your distributed challenge 7 23 uoouownooq SIQDIIDAY Z
109. psum 2 cached From CNN Lorem ipsum 3 9 50 14 AM From CNN Lorem ipsum 2 cached From Economist Lorem ipsum 2 9 50 14 AM From Reuters Lorem ipsum 5 From Reuters Lorem ipsum 8 9 50 14 AM From AP Lorem ipsum 3 From Reuters Lorem ipsum 9 9 50 14 AM From Bloomberg Lorem ipsum 2 From AP Lorem ipsum 5 9 50 14 AM From Reuters Lorem ipsum 6 From Bloomberg Lorem ipsum 3 9 50 14 AM From NY Times Lorem ipsum 2 Publishing Application Subscribing Application ested in only a fraction of the data available on those topics Extraneous uninteresting or obsolete data puts a drain on your network and CPU resources and complicates your application logic Fortunately RTI Data Distribution Service can perform much of your filtering and data reducti on for you Data reduction is a general term for discarding unnecessary or irrele vant data so that you can spend you time processing the data you care about You can define the set of data that is relevant to you based on m 5 4 lts content Content based filters can examine any field in your data based on a variety of criteria such as whether numeric values meet various equality and inequality relationship or whether string values match certain regular expression patterns For example you may choose to distribute a stream of stock prices using a single topic but indicate that you re interes
110. pter on Configuring QoS with XML in the RTI Data Distribution Service User s Manual History Depth The DDS specification which RTI Data Distribution Service implements recognizes two kinds of history KEEP_ALL and KEEP_LAST KEEP_ALL history indicates that the application wants to see every data sample regardless of how old it is subject of course to lifespan and other QoS policies KEEP_LAST history indicates that only a certain number of back samples are relevant this number is indicated by a second parameter the history depth The depth value if any is ignored if the kind is set to KEEP_ALL To specify a default History policy of KEEP_LAST and a depth of 10 in a QoS profile lt history gt lt kind gt KEEP_LAST_HISTORY_QOS lt kind gt lt depth gt 10 lt depth gt lt history gt You can see this in the News example provided for C C Java and Ada in the file USER_QOS_PROFILES xml Lifespan Duration The Lifespan QoS policy contains a field duration that indicates for how long each sam ple remains valid The duration is measured relative to the sample s reception time stamp which means that it doesn t include the latency of the underlying transport To specify a Lifespan duration of six seconds lt lifespan gt lt duration gt lt sec gt 6 lt sec gt lt nanosec gt 0 lt nanosec gt lt duration gt lt lifespan gt You can see this in the News example provided for C C Ja
111. r your real time and enterprise systems RTI also provides a Java Message Service JMS application programming interface RTI Data Distribution Service directly interoperates at the wire protocol level with RTI Mes sage Service the world s highest performing JMS implementation RTI Message Service with its standard JMS interface then provides integration with a wide range of enter prise service busses and application gateways For more information about interoperability with other middleware implementations including IBM MQ Series please consult your RTI account representative 1 Ada support requires a separate add on product Ada 2005 Language Support for RTI Data Distribution Service 2 For more information about RTI Message Service visit on RTI the web at http www rti com products jms index html For performance benchmark results see http www rti com products jms latency throughput benchmarks html What Can RTI Data Distribution Service Do 1 2 What Can RTI Data Distribution Service Do Under the hood RTI Data Distribution Service goes beyond basic publish subscribe com munication to target the needs of applications with high performance real time and or low overhead requirements It features m m m m Peer to peer publish subscribe communications The most elegant flexible data communications model e Simplified distributed application programming e Time critical data flow with min
112. ram Hello in either Publisher or Subscriber mode It accepts the following parameters e pub sub Run as publisher or subscriber e verbose lIncreases output verbosity This script accepts other options which we will discuss in later chapters For Java users The native libraries used by the RTI Java API require the Visual Studio 2005 service pack 1 redistributable libraries on the target machine You can obtain this package from Microsoft or RTI For C C and C users Please use Microsoft Visual Studio 2005 service pack 1 or later or Visual Studio 2008 to build and run the examples Using Microsoft Visual Studio RTI Data Distribution Service includes solutions and project files for Microsoft Visual Stu dio in example C CPP CSHARP lt example gt win32 To use these solution files 1 Start Visual Studio 2 Select File Open Project Solution 3 In the File dialog select the solution file for your architecture the solution file for Visual Studio 2005 for 32 bit platforms is example C CPP CSHARP lt example gt win32 Hello i86Win32VS2005 sIn 1 If you are using an earlier version of Visual Studio you can obtain a no cost edition of Visual Studio 2005 or 2008 from Microsoft s web site Chapter 3 Getting Started with RTI Data Distribution 3 1 Service This chapter gets you up and running with RTI Data Distribution Service First you will build and run your first RTI Data Distribution Service
113. red in a batch use the DataWriter s flush operation 6 3 2 Running amp Verifying 1 To run and verify the new QoS parameters first run Hello_builtin using a sim ple reliable configuration batching is turned off Copy reliable xml from NDDSHOME example QoS to NDDSHOME example lt language gt Hello_builtin and rename it to USER_QOS_PROFILES xml Observe the results Figure 6 5 Initial Performance Results DOS run sub 6 12 Streaming Data over Unreliable Network Connections Figure 6 6 2 Next run the example again with a configuration that includes batching Copy high_throughput xml from NDDSHOME example QoS to NDDSHOME example lt language gt Hello_builtin and rename it to USER_QOS_PROFILES xml 3 Run Hello_builtin again Verify that the throughput numbers have improved Improved Performance Results ce DOS run sub 6 4 Streaming Data over Unreliable Network Connections Systems face unique challenges when sending data over lossy networks that also have high latency and low bandwidth constraints for example satellite and long range radio links While sending data over such a connection a middleware tuned for a high speed dedicated Gigabit connection would throttle unexpectedly cause unwanted timeouts and retransmissions and ultimately suffer severe performance degradation For example the transmission delay in satellite connections can be as much as 500 milli seconds to
114. rmance and reduces bandwidth consumption compared to the conventional approach in which each message is self describing and thus includes a substantial amount of metadata along with the actual data RTI Data Distribution Service takes an intermediate approach Just as objects in your application program belong to some data type data samples sent on the same Topic share a data type This type defines the fields that exist in the data samples and what their constituent types are users in the aerospace and defense industries will recognize 4 8 Compact Type Safe Data Programming with Data Types such type definitions as a form of Interface Definition Document IDD RTI Data Distri bution Service stores and propagates this meta information separately from the individ ual data samples allowing it to propagate samples efficiently while handling byte ordering and alignment issues for you Table 4 1 Example IDD 0 8 16 24 34 Message ID unsigned short Track ID unsigned short Position X short Position Y short Identity Position Z short Track Type unsigned short 12 unsigned short 4 Speed float This example IDD shows one legacy approach to type definition RTI supports multiple standard type definition formats that are machine readable as well as human readable With RTI you have a number of choices when it comes to defining and using data types You can choose one of these options or you can
115. roduct Ada 2005 Language Support for RTI Data Distribution Service 5 19 juowidojeasg pidpy 10 SUJ HOd UBISeq S sequences are loaned directly from the DataReader s cache in order to avoid unnecessary object allocations or copies When you are done with them call return_loan If you would rather read the samples into your own memory instead of taking a loan from the middleware simple pass in sequences in which the contents have already been deeply allocated The DataReader will copy over the state of the objects you provide to it instead of loaning you its own objects In this case you do not need to call return_loan L Number of samples to read If you are only prepared to read a certain number of samples at a time you can indicate that to the DataReader In most cases you will probably just use the constant LENGTH_UNLIMITED which indicates that you are prepared to handle as many samples as the DataReader has available L Sample state The sample state indicates whether or not an individual sample has been observed by a previous call to read The News example uses this state to decide whether or not to append cached to the data it prints out By pass ing a sample state mask to the DataReader you indicate whether you are inter ested in all samples only those samples you ve never seen before or only those samples you have seen before The most common value passed here is ANY_SAMPLE_STATE L View state T
116. s control durability for fault tolerance and much more The DDS QoS policies offer unprecedented flexible communications control The RTI Data Distribution Service User s Manual contains details about all the QoS policies offered by DDS 3 15 PHOM OII H 3 2 3 Publishers and DataWriters An application uses a DataWriter to publish data into a domain Once a DataWriter is created and configured with the correct QoS settings an application only needs to use the DataWriter s write operation to publish data A Publisher is used to group individual DataWriters You can specify default QoS behavior for a Publisher and have it apply to all the DataWriters in that Publisher s group Figure 3 3 Entities Associated with Publications Domain Participant The following code shows how to create a DataWriter in C participant gt create_datawriter COPIE data_writer DDS_DATAWRITER_QOS_DEFAULT NULL DDS_STATUS_MASK_NONE 3 16 A DDS DataWriter is analogous to a JMS TopicPublisher A DDS Publisher is analogous to the producing aspect of a JMS TopicSession OO Sai Listener Data Distribution Service DDS 101 In Ada it looks like this data_writer participant Create_DataWriter ESTOS DDS Publisher DATAWRITER_QOS_DEFAULT QoS null Listener DDS STATUS_MASK_ NONE As you can see each DataWriter is tied to a single topic All data publis
117. seeecesessessseseeceneeseseeneesesceeesesesnaneneseees 1 2 1 1 1 Reduce Risk Through Performance and Availability eeees 1 2 1 1 2 Reduce Cost through Ease of Use and Simplified Deployment cccs 1 3 1 1 3 Ensure Success with Unmatched Flexibility 00 0 ccccccecc cece csesteteeeeeeesesesnenens 1 3 1 1 4 Connect Heterogeneous Systems cccceccceseesssesetesenseeceeseessesesescsseseesssesesseeeees 1 4 1 1 5 Interoperate with Databases Event Engines and JMS Systems cscssee 1 4 What Can RTI Data Distribution Service D0 ccccceecescessssseseseseseesesescsesesesescscsesneseeees 1 5 2 Installing RTI Data Distribution Service 2 1 22 2 3 24 3 1 Installing RTI Data Distribution Service 0 c ccc eee ee ceeseseeeenesesseeeesesssseesenenesesees 2 1 2 1 1 Installing on a UNIX Based System cccesessesssssssssesesesesssesesesesesesesesesesesesssees 2 2 2 1 2 Installing on a Windows System ccccccssssssesessseeseesescsesesesescseseseseseecsssnsnecseeses 2 3 License Management isinumite ae hii eea a e iaai eia been tie ded dono dein 2 4 2 2 1 Installing the License File sasnrene sinnini e i 2 4 2 2 2 Adding or Removing License Management cccccccsssesesesceetesesescseeeeeeeeeees 2 5 Navigating the Directories issnin S aa eu i 2 5 Selecting a Development Environment ssssssssississssseesiesisstessesresiestistesnestenteseesneseeneesness 2 7 2 4 1 Using the Command Line Tools on UNIX bas
118. shes identical data samples and subscribes to them printing the received data to the terminal Edit the code to modify each data sample before it s published Open HelloWorld_publisher cxx In the code for publisher_main locate the for loop and add the bold line seen below which puts Hello World and a consec utive number in each sample that is sent for count 0 sample_count 0 count lt sample_count count printf Writing HelloWorld count d n count Modify the data to be sent here sprintf instance gt message Hello World d count retcode HelloWorld_writer gt write instance instance_handle if retcode DDS_RETCODE_OK printf write error d n retcode NDDSUtility sleep send_period 1 If you are using Visual Studio 2005 or Visual Studio 2008 consider using sprintf_s instead of sprintf sprintf_s instance gt msg 128 Hello World d count 4 12 Compact Type Safe Data Programming with Data Types 4 3 2 1 3 Java Instructions for Java Generate Java code from your IDL file with the following command replace the archi tecture name gt rtiddsgen ppDisable i86Linux2 6gcc3 4 3jdk with the name of your own architecture language Java example i86Linux2 6gcc3 4 3jdk replace HellowWorld idl alae ae ae The generated code publishes identical data samples and subscribes to them printing the received data to the terminal Edi
119. t Set your discovery peers to a list of all of the hosts that need to discover each other The list can contain hostnames and or IP addresses each entry should be of the form N builtin udpv4 lt hostname IP gt 2 If you do not have a network connection Some operating systems for example Microsoft Windows disable some functionality of their network stack when they detect that no network interfaces are available This can cause problems when applications try to open network connections e If your system supports shared memory set your discovery peers to N builtin shmem This will enable the shared memory transport only e If your system does not support shared memory or it is disabled set your discovery peers to the loopback address N builtin ud pv4 127 0 0 1 4 1 2 How to Set Your Discovery Peers As stated above in most cases you do not need to set your discovery peers explicitly If setting them is required there are two easy ways to do so L Set the NDDS_DISCOVERY_PEERS environment variable to a comma sepa rated list of the names or addresses of all the hosts that need to discover each other e On Windows systems For example set NDDS_DISCOVERY_PEERS 3 builtin udpv4 mypeerhost1 4 builtin udpv4 mypeerhost2 e On UNIX based systems For example if you are using csh or tesh setenv NDDS_DISCOVERY_PEERS 3 builtin udpv4 mypeerhost1 4 builtin udpv4 mypeerhost2 1 To see if
120. t lt value gt 1500 lt value gt lt element gt lt value gt lt property gt lt participant_qos gt The DomainParticipant s dds transport UDPv4 builtin parent message_size_max prop erty sets the maximum size of a datagram that will be sent by the UDP IPv4 transport If your application interfaces to your network over a transport other than UDP IPv4 the name of this property will be different In this case it is limiting all datagrams to the Streaming Data over Unreliable Network Connections MTU of the link assumed for the sake of this example to be equal to the MTU of Ether net At the same time the DataWriter is configured to send its samples on the network not synchronously when write is called but in a middleware thread This thread will flow datagrams onto the network at a rate determined by the FlowController identi fied by the flow_controller_name In this case the FlowController is a built in instance that allows all data to be sent immediately In a real world application you may want to use a custom FlowController that you create and configure in your application code Further information on this topic is beyond the scope of this example For more infor mation on asynchronous publishing see Section 6 4 1 in the RTI Data Distribution Service User s Manual You can also find code examples demonstrating these capabilities online in the Solutions area of the RTI Customer Portal accessible from https
121. t need to change to allow subscribers to filter on data contents 5 2 1 1 Implementation The C code looks like this DDSContentFilteredTopic cft participant gt create_contentfilteredtopic cftName c_str topic contentFilterExpression c_str noFilterParams Wit CEC INI 4 throw std runtime_error Unable to create ContentFilteredTopic The Topic and ContentFilteredTopic classes share a base class TopicDescription The variable contentFilterExpression in the above example code is a SQL expression see immediately below 5 5 juowdojeasg pidpy 10 SUJ HOd UBIseq S The corresponding code in Java looks like this ContentFilteredTopic cft participant create_contentfilteredtopic topic get_name filtered topic contentFilterExpression TaywtIL IL iit Gite cml throw new IllegalStateException Unable to create ContentFilteredTopic The Ada code to create a ContentFilteredTopic looks like this GEE DDS ContentFilteredTopic Ref_Access cftName DDS String DDS To_DDS_String DDS To_Standard_String topic Get_Name amp filtered begin cft participant Create_Contentfilteredtopic cftName topic contentFilterExpression ea DDS Finalize cftName ie Gre mol raem Put_Line Standard_Error Unable to create ContentFilteredTopic HSLuULn end if end In Ada ContentFilteredTopic class inherits from TopicD
122. t the code to modify each data sample before it s published Open HelloWorldPublisher java In the code for publisherMain locate the for loop and add the bold line seen below which puts Hello World and a consec utive number in each sample that is sent for Gm count Sys t count 0 sampleCount 0 count lt sampleCount aC tem out printin Writing HelloWorld count count Modify the instance to be written here instance msg Hello World count Write data wri ter write instance InstanceHandle_t HANDLE_NIL bry d Thread sleep sendPeriodMillis catch InterruptedException ix System err printiln INTERRUPTED break 1 The argument ppDisable tells the code generator not to attempt to invoke the C preprocessor usually cpp on UNIX systems and cl on Windows systems on the IDL file prior to generating code In this case the IDL file contains no preprocessor directives so no preprocessing is necessary However if the pre processor executable is already on your system path on Windows systems running the Visual Studio script vevars32 bat will do this for you you can omit this argument SOUDUWHO Ied PUD s yi qodo vy 4 3 2 1 1 Instructions for Ada Generate Ada code from your IDL file with the following command replace the archi tecture name i86Linux2 6gcc4 1 2 with the name of your own architecture rtiddsgen ppDisable l
123. ta the middleware will compare the current time with those timestamps and drop data when your specified Lifespan expires You can use the Lifespan QosPolicy to ensure that applications do not receive or act on data commands or messages that are too old and have expired J Durability Specifies whether or not the middleware will store and deliver previ ously published data to new DataReaders This policy helps ensure that DataRead ers get all data that was sent by DataWriters even if it was sent while the DataReader was disconnected from the network It can increase a system s toler ance to failure conditions Fault Tolerance for increased robustness and reduced risk I Liveliness Specifies and configures the mechanism that allows DataReaders to detect when DataWriters become disconnected or dead It can be used during system integration to ensure that systems meet their intended responsiveness specifications It can also be used during run time to detect possible losses of connectivity L Ownership and Ownership Strength Along with Ownership Strength Ownership specifies if a DataReader can receive data from multiple DataWriters at the same time By default DataReaders for a given topic can receive data from any DataW riter for the same topic But you can also configure a DataReader to receive data from only one DataWriter at a time The DataWriter with the highest Ownership Strength value will be the owner of the topic and the one
124. ta is published faster than this rate the mid dleware will discard the intervening samples Such a filter is most often used to down sample high rate periodic data see also Receiv ing Notifications When Data Delivery Is Late Section 5 5 but it can also be used to limit data rates for aperiodic but bursty data streams Time based filters have several applications J You can limit data update rates for applications in which rapid updates would be unnecessary or inappropriate For example a graphical user interface should typically not update itself more than a few times each second more frequent updates can cause flickering or make it difficult for a human operator to perceive the correct values I You can reduce the CPU requirements for less capable subscribing machines to improve their performance If your data stream is reliable helping slow readers keep up can actually improve the effective throughput for all readers by prevent ing them from throttling the writer _ In some cases you can reduce your network bandwidth utilization because the writer can transparently discard unwanted data before it is even sent on the net work Implementation Time based filters are specified using the TimeBasedFilter QoS policy It only applies to DataReaders For more information about this QoS policy consult the online API documentation Open ReadMe html and select the API documentation for your language then select Modules DDS API Refer
125. ted only in the price of IBM and only when that price goes above 20 Subscribing Only to Relevant Data I How old it is You can indicate that data is relevant for only a certain period of time its lifespan and or that you wish to retain only a certain number of data samples a history depth For example if you are interested in the last ten articles from each news outlet you can set the history depth to 10 l How fast it s updated Sometimes data streams represent the state of a moving or changing object for example an application may publish the position of a mov ing vehicle or the changing price of a certain financial instrument Subscribing applications may only be able to or interested in processing this data at a cer tain maximum rate For example if the changing state is to be plotted in a user interface a human viewer is unlikely to be able to process more than a couple of changes per second If the application attempts to process updates any faster it will only confuse the viewer and consume resources unnecessarily 2 1 Content Based Filtering A DataReader can filter incoming data by subscribing not to a given Topic itself but to a ContentFilteredTopic that associates the Topic with an SQL like expression that indicates which data samples are of interest to the subscribing application Each subscribing application can specify its own content based filter as it desires publishing applica tions code does no
126. the process of generating example code from your own data type Generating Code with rtiddsgen Don t worry about how types are defined in detail for now we cover it in Chapter 3 of the RTI Data Distribution Service User s Manual For this example just copy and paste the following into a new file HelloWorld idl const long HELLO _MAX STRING_SIZE 256 struct HelloWorld string lt HELLO_MAX STRING_SIZE gt message ier Next we will invoke the rtiddsgen code generator which can be found in the NDDSHOME scripts directory that should already be on your path to create defini tions of your data type in a target programming language including logic to serialize and deserialize instances of that type for transmission over the network Then we will build and run the generated code For a complete list of the arguments rtiddsgen understands and a brief description of each of them run it with the help argument More information about rtiddsgen includ ing its command line parameters and the list of files it creates can be found in Section 3 7 of the User s Manual SOUDUNOLSd PUD s yi qodo vy 4 3 2 1 2 Instructions for C Generate C code from your IDL file with the following command replace the archi CH tecture name i86Linux2 6gcc3 4 3 with the name of your own architecture gt rtiddsgen ppDisable language C example i86Linux2 6gcc3 4 3 replace HelloWorld idl The generated code publi
127. tly starts up will not receive that data Durability like some other QoS policies has request offer semantics the DataWriter must offer a level of service that is greater than or equal to the level of service requested by the DataReader For example a DataReader may request only volatile durability while the DataWriter may offer transient durability In such a case the two will be able to commu nicate However if the situation were reversed they would not be able to communicate Running amp Verifying Run the NewsPublisher and wait several seconds Then start the NewsSubscriber Look at the time stamps printed next to the received data you will see that the subscrib ing application receives data that was published before it started up Now do the same thing again but first modify the configuration file by commenting the durability configuration You will see that the subscribing application does not receive any data that was sent prior to when it joined the network 1 Ada support requires a separate add on product Ada 2005 Language Support for RTI Data Distribution Service Caching Data Within the Middleware 5 4 Caching Data Within the Middleware When you receive data from the middleware in your subscribing application you may be able to process all of the data immediately and then discard it Frequently however you will need to store it somewhere in order to process it later Since you ve already expressed
128. to receive a sample at least once per second Writing network code to connect a few nodes is deceptively easy Making that code scale handle all the error scenarios you will eventually face work across platforms keep current with technology and adapt to unexpected future requirements is another matter entirely The initial cost of a custom design may seem tempting but beware robust architectures take years to evolve Going with a fire tested widely used design assures you the best performance and functionality that will scale with your distributed application as it matures And it will minimize the profound cost of going down the wrong path QWOTIOM L Chapter 2 Installing RTI Data Distribution Service 2 1 RTI Data Distribution Service is delivered as static and dynamic libraries with develop ment tools examples and documentation that will help you use the libraries This chapter includes I Installing RTI Data Distribution Service LI License Management LI Navigating the Directories E Selecting a Development Environment Next Chapter gt Getting Started with RTI Data Distribution Service Installing RTI Data Distribution Service RTI Data Distribution Service is available for installation in the following forms depend ing on your needs and your license terms LJ In a single package as part of RTI Professional Edition which includes both host development and target deployment files If you downloaded an e
129. to the middleware how long your data remains relevant see Subscribing Only to Relevant Data Section 5 2 wouldn t it be nice if you could take advantage of the middleware s own data cache rather than implementing your own You can When a DataReader reads data from the network it places the samples in order into its internal cache When you re ready to view that data either because you received a noti fication that it was available or because you decided to poll you use one of two fami lies of methods I take Read the data from the cache and simultaneously remove it from that cache Future access to that DataReader s cache will not see any data that was pre viously taken from the cache This behavior is similar to the behavior of receive methods provided by traditional messaging middleware implementa tions The generated Ada example uses this method I read Read the data from the cache but leave it in the cache so that it can poten tially be read again subject to any lifespan or history depth you may have speci fied The News example for C C and Java uses this method When you read or take data from a DataReader you can indicate that you wish to access all of the data in the cache all up to a certain maximum number of samples all of the new samples that you have never read before and or various other qualifiers If your topic is keyed you can choose to access the samples of all instances at once or you can
130. ution Service PHOM OIISH 3 2 4 Subscribers and DataReaders A DataReader is the point through which a subscribing application accesses the data that it has received over the network Just as Publishers are used to group DataWriters Subscribers are used to group DataReaders Again this allows you to configure a default set of QoS parameters and event han dling routines that will apply to all DataReaders in the Sub scriber s group Figure 3 4 Entities Associated with Subscriptions Domain Participant N Domain l The following code demonstrates how to create a DataReader CH data_reader participant gt create_datareader topic DDS_DATA_AVAILABLE_STATUS A DDS DataReader is analogous to a JMS TopicSubscriber A DDS Subscriber is analogous to the consuming aspect of a JMS TopicSession DDS_DATAREADER_QOS_DEFAULT QoS amp listener Listener Each DataReader is tied to a single topic A DataReader will only receive data that was published on its Topic 3 18 Data Distribution Service DDS 101 Here is the analogous code in Java StringDataReader dataReader StringDataReader participant create_datareader COPIEI Subscriber DATAREADER_QOS_DEFAULT QoS new HelloSubscriber Listener StatusKind DATA_ AVAILABLE STATUS And in Ada dataReader DDS Builtin_String_ DataReader Narrow participant Create_DataReader top
131. va and Ada in the file USER_QOS_PROFILES xml 1 Ada support requires a separate add on product Ada 2005 Language Support for RTI Data Distribution Service 5 9 juowidojeasg pidpy 10 SU1 HOd UBIseq S 5 2 2 2 5 10 Running amp Verifying The News example never takes samples from the middleware it only reads samples so data samples that have already been viewed by the subscribing application remain in the middleware s internal cache until they are expired by their history depth or lifespan duration contract These previously viewed samples are displayed by the subscribing application as cached to make them easy to spot See how CNN articles are expired It s important to understand that the data type used by this example is keyed on the name of the news outlet and that the history depth is databases the key of a DDS Topic is like enforced on a per instance basis You can see the the primary key of a database table effect in Figure 5 3 even though Reuters pub and the instance corresponding to that lishes articles faster than CNN the Reuters arti key is like the table row corresponding cles do not starve out the CNN articles each to that primary key outlet gets its own depth samples Figure 5 3 only shows articles from CNN and Reuters because that makes it easier to fit more data on the page If you run the example without a content filter you will see the same effect across all news outlets
132. valuation of RTI Data Distribution Service from the RTI website at no cost this is the distribu tion you have For installation instructions please see the RTI Data Distribution Service Professional Edition Getting Started Guide RTI_DDS_ProfessionalEdition_GettingStarted pdf e For Windows users Your installation package is an executable installer application that installs a specific Windows architecture 2 1 UOHDI D SU Z 2 1 1 2 2 e For Linux users Your installation package is a sh file that installs a specific Linux architecture LJ In separate host and target packages This distribution is useful for those cus tomers who develop and deploy on different platforms or who deploy on multi ple platforms RTI also delivers support for embedded platforms this way To request access to additional RTI host or target platforms please contact your RTI account representative e For Windows users You have at least two zip archives one for your host platform and at least one target platform Expand them into the same directory a directory of your choice e For users of other operating systems You have at least two tar gz archives one for your host platform and at least one target platform Expand them into the same directory a directory of your choice Installing on a UNIX Based System If you are using the RTI Data Distribution Service Professional Edition installer please see the RTI Data Distribution Service
133. w often the middleware will piggyback a heartbeat onto a data message if the middleware is configured to cache 10 samples for example and heartbeats_per_max_samples is set to 5 a heartbeat will be piggybacked unto every other sample If heartbeats_per_max_samples is set equal to max_samples this means that a heartbeat will be sent with each sample Make Sure Repair Packets Don t Exceed Bandwidth Limitation Applications can configure the maximum amount of data that a DataWriter will resend at a time using the max_bytes_per_nack_response parameter For example if a DataReader sends a negative acknowledgement NACK indicating that it missed 20 Streaming Data over Unreliable Network Connections 6 4 1 4 samples each 10 KB in size and max_bytes_per_nack_response is set to 100 KB the DataWriter will only send the first 10 samples The DataReader will have to NACK again to receive the remaining 10 samples In the following example we limit the number of bytes so that we will never send more data than a 256 Kb s 1 ms latency link can handle over one second lt datawriter_qos gt lt protocol gt lt rtps_reliable_writer gt lt max_bytes_per_nack_response gt 28000 lt max_bytes_per_nack_response gt lt rtps_reliable_ writer gt lt protocol gt lt datawriter_qos gt Use Batching to Maximize Throughput for Small Samples If your application is sending data continuously consider batching small samples t
134. whose data is delivered to DataReaders Data sent by all other DataWriters with lower Ownership Strength will be dropped by the middleware When the DataWriter with the highest Ownership strength loses its liveliness as controlled by the Liveliness QosPolicy or misses a deadline as controlled by the Deadline QosPolicy or whose application quits dies or otherwise disconnects the middleware will change ownership of the topic to the DataWriter with the highest Ownership Strength from the remaining DataWriters This QoS policy can help you build systems that have redundant elements to safeguard against component or application failures When systems have active and hot standby components the Ownership QosPolicy can be used to ensure that data from standby applications are only delivered in the case of the failure of the primary Compact Type Safe Data Programming with Data Types 4 3 Built in Support for Periodic Data L Deadline For a DataReader this QoS specifies the maximum expected elapsed time between arriving data samples For a DataWriter it specifies a commitment to publish samples with no greater than this elapsed time between them This policy can be used during system integration to ensure that applications have been coded to meet design specifications It can be used during run time to detect when systems are performing outside of design specifications Receiving applications can take appropriate actions to prevent tota
135. will assume that you want to install under C Program Files RTI you may replace references to C Pro gram Files RTI with the directory of your choice 2 Move the downloaded files into your newly created directory 3 Extract the distribution from the uncompressed files You will need a zip file util ity such as WinZip to help you Using our example path you will end up with C Program Files RTI ndds 4 x 2 3 UOHDI D SU Z 2 2 2 2 1 2 4 4 Optional If you want to use the TCP transport included with RTI Data Distribu tion Service in a secure configuration you also need to install RTI TLS Support and OpenSSL To purchase RTI TLS Support please contact your RTI account repre sentative 5 Read License Management Section 2 2 License Management Some distributions of RTI Data Distribution Service require a license file in order to run for example those provided for evaluation purposes or on a subscription basis If your RTI Data Distribution Service distribution requires a license file you will receive one from RTI via email If you have licenses files for both RTI Data Distribution Service and RTI Message Service you can concatenate both into one file A single license file can be used to run on any architecture and is not node locked You are not required to run a license server Installing the License File Save the license file in any location of your choice the locations checked by t
136. y are not sent on the network flushed immediately when the application writes them this can potentially increase latency However if the application sends data faster than the network can support an increased share of the network s available bandwidth will be spent on acknowledge ments and resending dropped data In this case reducing that meta data overhead by turning on batching could decrease latency even while increasing throughput Only an evaluation of your system s requirements and a measurement of its actual performance will indicate whether batching is appropriate Fortunately it is easy to enable and tune batching as you will see below Batching is particularly useful when the system has to send a large number of small messages at a fast rate Without this feature enabled you may observe that your maxi mum throughput is less than the maximum bandwidth of your network Simultane ously you may observe high CPU loads In this situation the bottleneck in your system is the ability of the CPU to send packets through the OS network stack For example in some algorithmic trading applications market data updates arrive at a rate of from tens of thousands of messages per second to over a million each update is some hundreds of bytes in size It is often better to send these updates in batches than to publish them individually Batching is also useful when sending a large number of small samples over a connection where the bandwidth is s
137. you are running in best effort mode or in a limited reliability mode e g you have configured your History QoS policy to only keep the most recent sample you may see non zero values here I Current lost samples The number of samples that were lost in transit and could not be repaired since the last status line was printed See the description of the previous column for information about what values to expect here L Average samples per second The mean number of data samples received per second since the subscribing application started running By default these exam ple applications send data samples that are 1 KB in size You can change this by passing a different size in bytes to the publishing application with size L Current samples per second The number of data samples received since the sub scribing application printed the last status line 6 3 SOUDWJOLeg YIH 10 SUI HOd UBIseg 9 6 2 6 4 L Throughput megabits per second The throughput from the publishing applica tion to the subscribing application in bits per second since the subscribing application printed the previous status line The value in this column is equiva lent to the current samples per second multiplied by the number of bits in an individual sample With small sample sizes the fixed cost of traversing your operating system s network stack is greater than the cost of actually transmitting the data as you increase the sample size you
138. your path already you can run this script before running rtiddsgen e If you do not have Microsoft Visual Studio installed This is often the case with Java users You can either choose not to use a preprocessor or to obtain a no cost version of Visual Studio from Microsoft s web site Get your project files ready If you installed RTI Data Distribution Service in a directory that is shared by mul tiple users for example in C Program Files on a Windows system or opt or Nocal on a UNIX based system you may prefer to build and edit the examples in a directory of your own so you do not interfere with other users Depending on your file permissions you may have to copy them somewhere else If you would like copy the directory NDDSHOME example to a location of your choice Where you see NDDSHOME example mentioned in the instructions below substitute your own copied directory instead 3 3 PHOM OIISH E 3 1 1 2 3 4 e On Windows systems If you chose to install RTI Data Distribution Service in C Program Files or another system directory Microsoft Visual Studio may present you with a warning message when you open a solution file from the installation directory If you see this dialog you may want to copy the example directory somewhere else as described above Security Warning for Hello The Hello project File has been customized and could present a security risk by executing custom build steps when opened in Mi
139. your platform supports RTI s multicast network and shared memory transports see the RTI Data Distribution Service Platform Notes RTI_DDS_PlatformNotes pdpf 4 3 SOUDUWO ed PUD s yi qodo vy 4 2 4 4 I Set the discovery peer list in your XML QoS configuration file For example to turn on shared memory only lt participant_qos gt lt discovery gt a The initial_peers list are those addresses to which the middleware will send discovery announcements e lt initial_peers gt lt element gt 4 builtin shmem lt element gt lt initial_peers gt a The multicast_receive_addresses list identifies where the domain participant listens for multicast announcements from others Set this list to an empty value to disable listening over multicast 55 lt multicast_receive_addresses gt lt empty gt lt multicast_receive_addresses gt lt discovery gt lt participant_qos gt For more information please see the RTI Data Distribution Service Platform Notes User s Manual and online documentation from the main page select Modules Infrastructure Module QoS Policies DISCOVERY Customizing Behavior QoS Configuration Almost every object in the DDS API is associated with QoS policies that govern its behavior These policies govern everything from the amount of memory the object may use to store incoming or outgoing data to the degree of reliability required to the amount of meta traffic th

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