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<title>ActiveMQ Artemis JMS Durable Subscription Example</title>
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<h1>JMS Durable Subscription Example</h1>
<pre>To run the example, simply type <b>mvn verify</b> from this directory, <br>or <b>mvn -PnoServer verify</b> if you want to start and create the server manually.</pre>
<p>This example demonstrates a clustered JMS durable subscription.
Normally durable subscriptions exist on a single node and can only have one subscriber at any one time,
however, with ActiveMQ Artemis it's possible to create durable subscription instances with the same name and client-id
on different nodes of the cluster, and consume from them simultaneously.
This allows the work of processing messages from a durable subscription to be spread across the cluster in
a similar way to how JMS Queues can be load balanced across the cluster
</p>
<p>In this example we first configure the two nodes to form a cluster, then we then create a durable subscriber
with the same name and client-id on both nodes, and we create a producer on only one of the nodes.</p>
<p>We then send some messages via the producer, and we verify that the messages are round robin'd between
the two subscription instances. Note that each durable subscription instance with the same name and client-id
<b>does not</b> receive its own copy of the messages. This is because the instances on different nodes form a
single "logical" durable subscription, in the same way multiple JMS Queue instances on different nodes
form a single "local" JMS Queue</p>
<p>This example uses JNDI to lookup the JMS Queue and ConnectionFactory objects. If you prefer not to use
JNDI, these could be instantiated directly.
<p>Here's the relevant snippet from the server configuration, which tells the server to form a cluster between the two nodes
and to load balance the messages between the nodes.</p>
<p>The cli create method will define this section by default if you use --clustered as a parameter</p>
<pre class="prettyprint">
<code><cluster-connection name="my-cluster">
<address>jms</address>
<retry-interval>500</retry-interval>
<use-duplicate-detection>true</use-duplicate-detection>
<message-load-balancing>STRICT</message-load-balancing>
<max-hops>1</max-hops>
<discovery-group-ref discovery-group-name="my-discovery-group"/>
</cluster-connection>
</code>
</pre>
<p>For more information on ActiveMQ Artemis load balancing, and clustering in general, please see the clustering
section of the user manual.</p>
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