Enabling multiple server support by using the Liberty embedded messaging provider

The batch environment can be set up to have servers function as batch dispatchers while other servers function as batch executors. Batch dispatchers accept requests from external clients and make them available to the batch executors. The batch executors receive requests that match its defined capabilities and execute those requests. Batch dispatchers and batch executors communicate by using Java Messaging Service (JMS).

<!-specify the ports for the messaging engine.
The ports in this example are the default ports.
This element is not needed when the default ports are used. -->
<wasJmsEndpoint host="*" 
		  wasJmsPort="7280" 
		  wasJmsSSLPort="7290" 
		  enabled="true"> 
</wasJmsEndpoint>

<messagingEngine>
	<!- queue for batch jms message. -->
	<queue id="batchLibertyQueue" 
		forceReliability="ReliablePersistent" 
		receiveAllowed="true"/>
</messagingEngine>

To configure batch dispatcher and executor that uses the Liberty embedded messaging provider:

1. Configure the batch JMS dispatcher.
   1. Enable JMS support by adding the wasJmsClient-2.0 feature to the feature manager in your server.xml.
   2. Add the batchJmsDispatcher element to your server.xml on the server that hosts the batch dispatcher.

      <batchJmsDispatcher connectionFactoryRef={reference to a configured JMS connection factory}
      	queueRef={reference to a configured JMS queue} />

      Note: If you do not specify the connectionFactoryRef and queueRef attributes, the default value for connectionFactoryRef is batchConnectionFactory and the default value for queueRef is batchJobSubmissionQueue. You can specify the batchJmsDispatcher element as <batchJmsDispatcher />. You still must configure the batchConnectionFactory JMS connection factory and the JMS batchJobSubmissionQueue queue in the server.xml file.
   3. Add the corresponding JMS connection factory and JMS queue to the server configuration. This is not specific to batch configuration.
      The following example illustrates the batch JMS dispatcher configuration and its JMS configuration.

      Note: The remoteServerAddress attribute points to the host:port of the server that is hosting the Liberty messaging engine.

      
      <batchJmsDispatcher connectionFactoryRef="batchConnectionFactory"
      		    queueRef="batchJobSubmissionQueue" />
      
      <jmsConnectionFactory id="batchConnectionFactory">
      	 <properties.wasJms remoteServerAddress="host:7280:BootstrapBasicMessaging">
      	 </properties.wasJms>
      </jmsConnectionFactory>
      
      <jmsQueue id="batchJobSubmissionQueue">
      	 <properties.wasJms deliveryMode="Persistent" 
      			    queuename="batchLibertyQueue">
      	 </properties.wasJms>
      </jmsQueue>

      Note: Ensure that you are referencing a jmsConnectionFactory element, as shown in the example, and not a jmsQueueConnectionFactory element. Using a jmsQueueConnectionFactory element will not work. Your configuration should include both a jmsConnectionFactory element and a jmsQueue element, but not a jmsQueueConnectionFactory element.
2. Configure the batch JMS executor.
   1. Enable JMS support by adding the wasJmsClient-2.0 feature to the feature manager in your server.xml.
   2. Add the batchJmsExecutor element to your server.xml file on the server that hosts the batch executor.

      <batchJmsExecutor activationSpecRef={configured activation specification}
      	queueRef={reference to the configured JMS queue} />

      Note: If you do not specify the activationSpecRef and queueRef attributes, the default value for activationSpecRef is batchActivationSpec and the default value for queueRef is batchJobSubmissionQueue. You can specify the batchJmsExecutor element as <batchJmsExecutor />. You still must configure the JMS activation specification for batchActivationSpec and the batchJobSubmissionQueue JMS queue in the server.xml file.
   3. Add the corresponding JMS activation specification and JMS queue to the server configuration. This is not specific to batch configuration.
   4. Optional: If you want batch group security enforcement, add the corresponding operation group name stanzas to the batchJmsExecutor element as shown in the following example.

      <batchJmsExecutor activationSpecRef={configured activation specification}
                    queueRef={reference to the configured JMS queue} >
              <operationGroup>GroupA</operationGroup>
       </batchJmsExecutor>

      Note: You must configure the security registry to support the previously listed group names.
   5. Define batch executor server capabilities by including a JMS message selector in the activation specification.
      • Filtering based on system defined properties:

        There is a set of batch dispatcher properties available on the batch JMS message that the batch executor can use to filter for inbound messages.

        • com_ibm_ws_batch_applicationName: the name of the batch application for the job request
        • com_ibm_ws_batch_moduleName: the module name of the batch application for the job request
        • com_ibm_ws_batch_componentName: the component name of the batch application for the job request
        Note: It is recommended that a message selector is specified with at least the com_ibm_ws_batch_applicationName property to ensure that the executor only receives jobs that it can process.
        The following example indicates the messageSelector attribute for the executor to accept a job for the application SimpleBatchJob and BonusPayout.

        messageSelector="com_ibm_ws_batch_applicationName = 'SimpleBatchJob' OR com_ibm_ws_batch_applicationName = 'BonusPayout'">

        The following example indicates the messageSelector attribute for the executor to accept a job for the application SimpleBatchJob.

        messageSelector="com_ibm_ws_batch_applicationName = 'SimpleBatchJob'">

      • Filtering based on user-defined properties:

        The batch dispatcher sets all job parameters that conform to the proper JMS message property on the batch dispatcher request message. These properties can also be used by the message selector to add extra filtering to the message selector. The property name, or identifier, must conform to JMS message property constraints. For example, the property is an unlimited length sequence of letters and digits, the first of which must be a letter. A letter is any character for which the method Character.isJavaLetter returns true, and includes '_' and '$'. A letter or digit is any character for which the method Character.isJavaLetterOrDigit returns true. Check JMS Javadoc for more information on JMS message selector.

        The following example illustrates a possible message selector by using the com_ibm_ws_batch_applicationName property and a job parameter specialCapability.

        messageSelector="com_ibm_ws_batch_applicationName = 'SimpleBatchJob' AND specialCapability = 'superCapability'">

      The following example illustrates the batch JMS executor configuration and its JMS configuration:

      <batchJmsExecutor activationSpecRef="batchActivationSpec" queueRef="batchJobSubmissionQueue"/>
      
      <jmsActivationSpec id="batchActivationSpec" >
              <properties.wasJms destinationRef="batchJobSubmissionQueue"  
                      messageSelector="(com_ibm_ws_batch_applicationName = 'SimpleBatchJob' OR com_ibm_ws_batch_applicationName = 'BonusPayoutCDI')"
                      destinationType="javax.jms.Queue"
                      remoteServerAddress="host:7280:BootstrapBasicMessaging">
              </properties.wasJms>
      </jmsActivationSpec>
      
      <jmsQueue id="batchJobSubmissionQueue">  
              <properties.wasJms deliveryMode="Persistent"
                      queueName="batchLibertyQueue">
              </properties.wasJms>
      </jmsQueue>

3. Install your batch application on the server. For more information, see Deploying applications in Liberty.
   Note: To delay delivery of job messages, submit the job specifying a job parameter of com_ibm_ws_batch_message_deliveryDelay that is set to the number of milliseconds to delay delivery of the message to an executor server.

   To alter the priority of the job message, submit the job specifying a job parameter of com_ibm_ws_batch_message_priority that is set to a valid JMS Message priority (0-9). The JMS specification defines the default message priority as '4' with zero as the lowest priority and nine as the highest.

   Restarting a failed job uses the same delay and priority as the original job unless a different value is specified as a job parameter on restart. Priority is propagated to messages for multi-server partitions, but the delivery delay is not propagated.