Configure durable subscribers

 

As discussed earlier, there might still be good reasons to use the multiple queue approach for durable subscriptions. Durable subscriptions are likely to have a longer life span, so it is possible that a large number of unretrieved messages could accumulate on the queue.

Therefore, the durable subscriber queue name property is set in the Topic object (that is, at a more manageable level than TopicConnectionFactory). This enables you to specify a number of different subscriber queue names, without needing to re-create multiple objects starting from the TopicConnectionFactory.

We can set the durable subscriber queue name in either of the following ways:

• Use the WebSphere MQ JMS administration tool (for JNDI retrieved objects) to set the BROKERDURSUBQ property

• Use the setBrokerDurSubQueue() method in your program:

  // Set the MQTopic durable subscriber queue name using
  // the multi-queue approach
  sportsTopic.setBrokerDurSubQueue("SYSTEM.JMS.D.FOOTBALL.*");
  

  Once the Topic object is initialized, it is passed into the TopicSession createDurableSubscriber() method to create the specified subscription:

  // Create a durable subscriber using our earlier Topic
  TopicSubscriber sub = new session.createDurableSubscriber
                                              (sportsTopic, "D_SUB_SPORT_001");
  

For durable subscriptions, the queue name you provide must start with the following characters:

• SYSTEM.JMS.D.

To select a shared queue approach, specify an explicit queue name, where the named queue is the one to use for the shared queue. The queue that you specify must already physically exist before you create the subscription.

To select the multiple queue approach, specify a queue name that ends with the * character. Subsequently, each subscriber that is created with this queue name creates an appropriate dynamic queue, for exclusive use by that subscriber. MQ JMS uses its own internal model queue to create such queues. Therefore, with the multiple queue approach, all required queues are created dynamically.

When you use the multiple queue approach, we cannot specify an explicit queue name. However, we can specify the queue prefix. This enables you to create different subscriber queue domains. For example, you could use:

• SYSTEM.JMS.D.MYDOMAIN.*

The characters that precede the * character are used as the prefix, so that all dynamic queues that are associated with this subscription have queue names that start with SYSTEM.JMS.D.MYDOMAIN.

We cannot change the queue used by a durable subscriber. To do so, for example to move from the multiple queue approach to the single queue approach, first delete the old subscriber (using the unsubscribe() method) and create the subscription again from new. This removes any unconsumed messages on the durable subscription.

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