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<title>ActiveMQ JMS Clustered Grouping Example</title>
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<h1>JMS Clustered Grouping Example</h1>
<p>This example demonstrates how to ensure strict ordering across a cluster using clustered message grouping</p>
<p>We create 3 nodes each with a grouping message handler, one with a Local handler and 2 with a Remote handler.</p>
<p>The local handler acts as an arbitrator for the 2 remote handlers, holding the information on routes and communicating
the routing info with the remote handlers on the other 2 nodes</p>
<p>We then send some messages to each node with the same group id set and ensure the same consumer receives all of them</p>
<p>Here's the relevant snippet from the server configuration that has the local handler</p>
<pre>
<code>
<cluster-connections>
<cluster-connection name="my-cluster">
<address>jms</address>
<connector-ref>netty-connector</connector-ref>
<retry-interval>500</retry-interval>
<use-duplicate-detection>true</use-duplicate-detection>
<forward-when-no-consumers>true</forward-when-no-consumers>
<max-hops>1</max-hops>
<discovery-group-ref discovery-group-name="my-discovery-group"/>
</cluster-connection>
</cluster-connections>
<grouping-handler name="my-grouping-handler">
<type>LOCAL</type>
<address>jms</address>
<timeout>5000</timeout>
</grouping-handler>
</code>
</pre>
<p>Here's the relevant snippet from the server configuration that has the remote handlers</p>
<pre>
<code>
<cluster-connections>
<cluster-connection name="my-cluster">
<address>jms</address>
<retry-interval>500</retry-interval>
<use-duplicate-detection>true</use-duplicate-detection>
<forward-when-no-consumers>true</forward-when-no-consumers>
<max-hops>1</max-hops>
<discovery-group-ref discovery-group-name="my-discovery-group"/>
</cluster-connection>
</cluster-connections>
<grouping-handler name="my-grouping-handler">
<type>REMOTE</type>
<address>jms</address>
<timeout>5000</timeout>
</grouping-handler>
</code>
</pre>
<p>For more information on ActiveMQ clustering and grouping see the clustering and grouping
section of the user manual.</p>
<h2>Example step-by-step</h2>
<p><i>To run the example, simply type <code>mvn verify -Pexample</code> from this directory</i></p>
<ol>
<li> Get an initial context for looking up JNDI from server 0.</li>
<pre class="prettyprint">
<code>ic0 = getContext(0);</code>
</pre>
<li>Look-up the JMS Queue object from JNDI</li>
<pre class="prettyprint">
<code>Queue queue = (Queue)ic0.lookup("/queue/exampleQueue");</code>
</pre>
<li>Look-up a JMS Connection Factory object from JNDI on server 0</li>
<pre class="prettyprint">
<code>ConnectionFactory cf0 = (ConnectionFactory)ic0.lookup("/ConnectionFactory");</code>
</pre>
<li>Get an initial context for looking up JNDI from server 1.</li>
<pre class="prettyprint">
<code>ic1 = getContext(1);</code>
</pre>
<li>Look-up a JMS Connection Factory object from JNDI on server 1</li>
<pre class="prettyprint">
<code>ConnectionFactory cf1 = (ConnectionFactory)ic1.lookup("/ConnectionFactory");
</code>
</pre>
<li>Get an initial context for looking up JNDI from server 2.</li>
<pre class="prettyprint">
<code>ic2 = getContext(2);</code>
</pre>
<li>Look-up a JMS Connection Factory object from JNDI on server 2</li>
<pre class="prettyprint">
<code>ConnectionFactory cf2 = (ConnectionFactory)ic2.lookup("/ConnectionFactory");
</code>
</pre>
<li>We create a JMS Connection connection0 which is a connection to server 0</li>
<pre class="prettyprint">
<code>connection0 = cf0.createConnection();</code>
</pre>
<li>We create a JMS Connection connection0 which is a connection to server 1</li>
<pre class="prettyprint">
<code>connection1 = cf1.createConnection();</code>
</pre>
<li>We create a JMS Connection connection0 which is a connection to server 2</li>
<pre class="prettyprint">
<code>connection2 = cf2.createConnection();</code>
</pre>
<li>We create a JMS Session on server 0</li>
<pre class="prettyprint">
<code>Session session0 = connection0.createSession(false, Session.AUTO_ACKNOWLEDGE);</code>
</pre>
<li>We create a JMS Session on server 1</li>
<pre class="prettyprint">
<code>Session session1 = connection1.createSession(false, Session.AUTO_ACKNOWLEDGE);</code>
</pre>
<li>We create a JMS Session on server 2</li>
<pre class="prettyprint">
<code>Session session2 = connection2.createSession(false, Session.AUTO_ACKNOWLEDGE);</code>
</pre>
<li>We start the connections to ensure delivery occurs on them</li>
<pre class="prettyprint">
<code>
connection0.start();
connection1.start();
connection2.start();</code>
</pre>
<li>We create JMS MessageConsumer objects on server 0</li>
<pre class="prettyprint">
<code>MessageConsumer consumer = session0.createConsumer(queue);</code>
</pre>
<li>We create a JMS MessageProducer object on server 0, 1 and 2</li>
<pre class="prettyprint">
<code>
MessageProducer producer0 = session0.createProducer(queue);
MessageProducer producer1 = session1.createProducer(queue);
MessageProducer producer2 = session2.createProducer(queue);</code>
</pre>
<li>We send some messages to server 0, 1 and 2 with the same groupid set</li>
<pre class="prettyprint">
<code>
final int numMessages = 10;
for (int i = 0; i < numMessages; i++)
{
TextMessage message = session0.createTextMessage("This is text message " + i);
message.setStringProperty(ActiveMQMessage.JMSXGROUPID, "Group-0");
producer0.send(message);
System.out.println("Sent messages: " + message.getText() + " to node 0");
}
for (int i = 0; i < numMessages; i++)
{
TextMessage message = session1.createTextMessage("This is text message " + (i + 10));
message.setStringProperty(ActiveMQMessage.JMSXGROUPID, "Group-0");
producer1.send(message);
System.out.println("Sent messages: " + message.getText() + " to node 1");
}
for (int i = 0; i < numMessages; i++)
{
TextMessage message = session2.createTextMessage("This is text message " + (i + 20));
message.setStringProperty(ActiveMQMessage.JMSXGROUPID, "Group-0");
producer2.send(message);
System.out.println("Sent messages: " + message.getText() + " to node 2");
}
</code>
</pre>
<li>We now consume those messages from server 0. We note the messages have all been sent to the same consumer on the same node</li>
<pre class="prettyprint">
<code>
for (int i = 0; i < numMessages * 3; i++)
{
TextMessage message0 = (TextMessage)consumer.receive(5000);
System.out.println("Got message: " + message0.getText() + " from node 0");
}
</code>
</pre>
<li>Finally, Be sure to close our resources!</li>
<pre class="prettyprint">
<code>
if (connection0 != null)
{
connection0.close();
}
if (connection1 != null)
{
connection1.close();
}
if (connection2 != null)
{
connection2.close();
}
if (ic0 != null)
{
ic0.close();
}
if (ic1 != null)
{
ic1.close();
}
if (ic2 != null)
{
ic2.close();
}</code>
</pre>
</ol>
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