175 lines
6.0 KiB
HTML
175 lines
6.0 KiB
HTML
<html>
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<head>
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<title>ActiveMQ JMS Colocated Failover 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 Colocated Failover Shared Store Example</h1>
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<p>This example demonstrates how you can colocate live and backup servers in the same VM. We do this by creating an
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HA Policy that is colocated. colocated means that backup servers can be created and maintained by live servers on behalf
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of other requesting live servers. In this example we create a colocated shared store server.
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<p>This example starts 2 live servers each with a backup server that backs up the other live server.</p>
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<p>The first live server will be killed and the backup in the second will become live</p>
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<p>The following shows how to configure the live servers to request and allow backups to be deployed</p>
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<pre class="prettyprint">
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<code><ha-policy>
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<shared-store>
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<colocated>
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<backup-port-offset>100</backup-port-offset>
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<backup-request-retries>-1</backup-request-retries>
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<backup-request-retry-interval>2000</backup-request-retry-interval>
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<max-backups>1</max-backups>
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<request-backup>true</request-backup>
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<master/>
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<slave/>
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</colocated>
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</shared-store>
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</ha-policy>
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</code>
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</pre>
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<p>notice that we have used a template to set some sensible defaults but overridden the backup strategy so back ups
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are full servers</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> Get an initial context for looking up JNDI for both servers</li>
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<pre class="prettyprint">
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<code>
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initialContext1 = getContext(1);
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initialContext = getContext(0);
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</code>
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</pre>
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<li>Look up the JMS resources from JNDI</li>
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<pre class="prettyprint">
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<code>
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Queue queue = (Queue)initialContext.lookup("/queue/exampleQueue");
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ConnectionFactory connectionFactory = (ConnectionFactory)initialContext.lookup("/ConnectionFactory");
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ConnectionFactory connectionFactory1 = (ConnectionFactory)initialContext1.lookup("/ConnectionFactory");
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</code>
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</pre>
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<li>Create a JMS Connections</li>
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<pre class="prettyprint">
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<code>
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connection = connectionFactory.createConnection();
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connection1 = connectionFactory1.createConnection();
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</code>
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</pre>
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<li>Create a *non-transacted* JMS Session with client acknowledgement</li>
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<pre class="prettyprint">
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<code>
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Session session = connection.createSession(false, Session.CLIENT_ACKNOWLEDGE);
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Session session1 = connection1.createSession(false, Session.CLIENT_ACKNOWLEDGE);
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</code>
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</pre>
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<li>Create a JMS MessageProducer</li>
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<pre class="prettyprint">
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<code>
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MessageProducer producer = session.createProducer(queue);
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MessageProducer producer1 = session1.createProducer(queue);
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</code>
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</pre>
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<li>Send some messages to both servers</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 message = session.createTextMessage("This is text message " + i);
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producer.send(message);
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System.out.println("Sent message: " + message.getText());
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message = session1.createTextMessage("This is another text message " + i);
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producer1.send(message);
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System.out.println("Sent message: " + message.getText());
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}
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</code>
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</pre>
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<li>Crash server #0, the live server</li>
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<pre class="prettyprint">
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<code>
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killServer(0);
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</code>
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</pre>
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<li>start the connection ready to receive messages</li>
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<pre class="prettyprint">
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<code>
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connection1.start();
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</code>
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</pre>
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<li>create a consumer</li>
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<pre class="prettyprint">
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<code>
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MessageConsumer consumer = session1.createConsumer(queue);
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</code>
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</pre>
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<li>Receive and acknowledge all of the sent messages, the backup server that is colocated with server 1
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will have become live and is now handling messages for server 0.</li>
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<pre class="prettyprint">
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<code>
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TextMessage message0 = null;
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for (int i = 0; i < numMessages; i++)
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{
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message0 = (TextMessage)consumer.receive(5000);
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System.out.println("Got message: " + message0.getText());
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}
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message0.acknowledge();
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</code>
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</pre>
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<li>Receive and acknowledge the rest of the sent messages from server 1.</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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message0 = (TextMessage)consumer1.receive(5000);
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System.out.println("Got message: " + message0.getText());
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}
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message0.acknowledge();
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</code>
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</pre>
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</pre>
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<li>And finally (no pun intended), <b>always</b> remember to close your JMS resources after use, in a <code>finally</code> block. Closing a JMS connection will automatically close all of its sessions, consumers, producer and browser objects</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 (connection != null)
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{
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connection.close();
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}
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if (initialContext != null)
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{
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initialContext.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 (initialContext1 != null)
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{
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initialContext1.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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