257 lines
8.8 KiB
HTML
257 lines
8.8 KiB
HTML
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<html>
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<head>
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<title>HornetQ JMS Symmetric Cluster Example</title>
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<link rel="stylesheet" type="text/css" href="../common/common.css" />
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<link rel="stylesheet" type="text/css" href="../common/prettify.css" />
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<script type="text/javascript" src="../common/prettify.js"></script>
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</head>
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<body onload="prettyPrint()">
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<h1>JMS Symmetric Cluster Example</h1>
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<p>This examples demonstrates a <b>symmetric cluster</b> set-up with HornetQ.</p>
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<p>HornetQ has extremely flexible clustering which allows you to set-up servers in
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many different topologies.</p>
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<p>The most common topology that you'll perhaps be familiar with if you are used to application
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server clustering is a <b>symmetric cluster</b>.</p>
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<p>With a symmetric cluster, the cluster is homogeneous, i.e. each node is configured the same
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as every other node, and every node is connected to every other node in the cluster.</p>
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<p>By connecting node in such a way, we can, from a JMS point of view, give the impression of distributed
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JMS queues and topics.</p>
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<p>The configuration used in this example is very similar to the configuration used by HornetQ
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when installed as a clustered profile in JBoss Application Server.</p>
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<p>To set up HornetQ to form a symmetric cluster we simply need to mark each server as <code>clustered</code>
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and we need to define a <code>cluster-connection</code> in <code>hornetq-configuration.xml</code>.</p>
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<p>The <code>cluster-connection</code> tells the nodes what other nodes to make connections to.
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With a <code>cluster-connection</code> each node that we connect to can either be specified
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indivually, or we can use UDP discovery to find out what other nodes are in the cluster.</p>
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<p>Using UDP discovery makes configuration simpler since we don't have to know what nodes are
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available at any one time.</p>
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<p>Here's the relevant snippet from the server configuration, which tells the server to form a cluster
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with the other nodes:</p>
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<pre class="prettyprint">
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<code>
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<cluster-connection name="my-cluster">
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<address>jms</address>
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<connector-ref>netty-connector</connector-ref>
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<retry-interval>500</retry-interval>
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<use-duplicate-detection>true</use-duplicate-detection>
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<forward-when-no-consumers>true</forward-when-no-consumers>
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<max-hops>1</max-hops>
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<discovery-group-ref discovery-group-name="my-discovery-group"/>
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</cluster-connection>
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</code>
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</pre>
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<p>In this example we create a symmetric cluster of six live nodes, and we also pair each live node
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with it's own backup node. (A backup node is not strictly necessary for a symmetric cluster).</p>
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<p>In this example will we will demonstrate this by deploying a JMS topic and Queue on all nodes of the cluster
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, sending messages to the queue and topic from different nodes, and verifying messages are received correctly
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by consumers on different nodes.</p>
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<p>For more information on configuring HornetQ clustering in general, please see the clustering
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section of the user manual.</p>
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<h2>Example step-by-step</h2>
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<p><i>To run the example, simply type <code>mvn verify</code> from this directory</i></p>
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<ol>
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<li>We instantiate a connection factory directly, specifying the UDP address and port for discovering
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the list of servers in the cluster.
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We could use JNDI to look-up a connection factory, but we'd need to know the JNDI server host and port for the
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specific server to do that, and that server might not be available at the time. By creating the
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connection factory directly we avoid having to worry about a JNDI look-up.
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In an app server environment you could use HA-JNDI to lookup from the clustered JNDI servers without
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having to know about a specific one.
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</li>
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<pre class="prettyprint">
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<code>
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ConnectionFactory cf = HornetQJMSClient.createConnectionFactoryWithHA("231.7.7.7", 9876);
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</code>
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</pre>
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<li>Directly instantiate JMS Queue and Topic objects</li>
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<pre class="prettyprint">
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<code>
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Queue queue = new HornetQQueue("exampleQueue");
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Topic topic = HornetQJMSClient.createHornetQTopic("exampleTopic");
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</code>
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</pre>
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<li>We create six connections, they should be to different nodes of the cluster in a round-robin fashion
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and start them.</li>
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<pre class="prettyprint">
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<code>
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connection0 = cf.createConnection();
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connection1 = cf.createConnection();
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connection2 = cf.createConnection();
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connection3 = cf.createConnection();
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connection4 = cf.createConnection();
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connection5 = cf.createConnection();
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connection0.start();
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connection1.start();
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connection2.start();
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connection3.start();
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connection4.start();
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connection5.start();
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</code>
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</pre>
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<li>We create a session on each connection.</li>
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<pre class="prettyprint">
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<code>
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Session session0 = connection0.createSession(false, Session.AUTO_ACKNOWLEDGE);
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Session session1 = connection1.createSession(false, Session.AUTO_ACKNOWLEDGE);
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Session session2 = connection2.createSession(false, Session.AUTO_ACKNOWLEDGE);
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Session session3 = connection0.createSession(false, Session.AUTO_ACKNOWLEDGE);
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Session session4 = connection1.createSession(false, Session.AUTO_ACKNOWLEDGE);
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Session session5 = connection2.createSession(false, Session.AUTO_ACKNOWLEDGE);
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</code>
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</pre>
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<li>We create a topic subscriber on each server.</li>
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<pre class="prettyprint">
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<code>
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MessageConsumer subscriber0 = session0.createConsumer(topic);
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MessageConsumer subscriber1 = session1.createConsumer(topic);
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MessageConsumer subscriber2 = session2.createConsumer(topic);
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MessageConsumer subscriber3 = session3.createConsumer(topic);
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MessageConsumer subscriber4 = session4.createConsumer(topic);
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MessageConsumer subscriber5 = session5.createConsumer(topic);
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</code>
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</pre>
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<li>We create a queue consumer on server 0.</li>
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<pre class="prettyprint">
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<code>
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MessageConsumer consumer0 = session0.createConsumer(queue);
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</code>
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</pre>
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<li>We create an anonymous message producer on server 2.</li>
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<pre class="prettyprint">
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<code>
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MessageProducer producer2 = session2.createProducer(null);
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</code>
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</pre>
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<li>We send 500 messages each to the queue and topic.</li>
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<pre class="prettyprint">
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<code>
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final int numMessages = 500;
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for (int i = 0; i < numMessages; i++)
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{
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TextMessage message1 = session2.createTextMessage("Topic message 1");
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producer2.send(topic, message1);
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TextMessage message2 = session2.createTextMessage("Queue message 1");
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producer2.send(queue, message2);
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}
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</code>
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</pre>
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<li>Verify all subscribers and consumer receive the messages.</li>
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<pre class="prettyprint">
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<code>
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for (int i = 0; i < numMessages; i++)
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{
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TextMessage received0 = (TextMessage)subscriber0.receive(5000);
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if (received0 == null)
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{
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return false;
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}
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TextMessage received1 = (TextMessage)subscriber1.receive(5000);
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if (received1 == null)
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{
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return false;
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}
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TextMessage received2 = (TextMessage)subscriber2.receive(5000);
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if (received2 == null)
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{
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return false;
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}
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TextMessage received3 = (TextMessage)subscriber3.receive(5000);
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if (received3 == null)
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{
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return false;
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}
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TextMessage received4 = (TextMessage)subscriber4.receive(5000);
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if (received4 == null)
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{
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return false;
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}
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TextMessage received5 = (TextMessage)subscriber5.receive(5000);
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if (received5 == null)
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{
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return false;
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}
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TextMessage received6 = (TextMessage)consumer0.receive(5000);
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if (received6 == null)
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{
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return false;
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}
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}
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</code>
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</pre>
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<li>Be sure to close our resources!</li>
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<pre class="prettyprint">
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<code>
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finally
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{
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if (connection0 != null)
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{
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connection0.close();
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}
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if (connection1 != null)
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{
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connection1.close();
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}
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if (connection2 != null)
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{
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connection2.close();
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}
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}
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</code>
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</pre>
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</ol>
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</body>
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</html>
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