activemq-artemis/examples/jms/transaction-failover
Martyn Taylor 56d6a47a83 ActiveMQ6-65 JBoss JMS1.1 -> Geronimo 2.0 spec jar
Replaces usage of the JBoss 1.1 API jar with the Geronimo JMS 2.0 jar.
The API is backwards compatibile.
2015-01-07 19:54:42 +00:00
..
src/main ACTIVEMQ6-43(reopened) : Replace License Headers on codebase 2015-01-05 13:14:25 -05:00
pom.xml ActiveMQ6-65 JBoss JMS1.1 -> Geronimo 2.0 spec jar 2015-01-07 19:54:42 +00:00
readme.html ACTIVEMQ6-43(reopened) : Replace License Headers on codebase 2015-01-05 13:14:25 -05:00

readme.html

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  <head>
    <title>ActiveMQ JMS Failover With Transaction Example</title>
    <link rel="stylesheet" type="text/css" href="../common/common.css" />
    <link rel="stylesheet" type="text/css" href="../common/prettify.css" />
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     <h1>JMS Failover With Transaction Example</h1>
     
     <p>This example demonstrates two servers coupled as a live-backup pair for high availability (HA), and a client
     connection failing over from live to backup when the live server is crashed.</p>
     <p>Failover behavior differs whether the JMS session is transacter or not.</p>
     <p>When a <em>transacted</em> JMS session is used, once-and-only once delivery is guaranteed.</p>
     <ul>
        <li>if the failover occurs while there is an in-flight transaction, the transaction will be flagged as <em>rollback only</em>. In that case, the JMS client 
           will need to retry the transaction work.</li>
        <li>if the failover occurs while there is <em>no</em> in-flight transaction, the failover will be transparent to the user.</li>
     </ul>
     <p>ActiveMQ also provides an example for <a href="../non-transactional-failover/readme.html">non-transaction failover</a>.</p>
     <p>For more information on ActiveMQ failover and HA, and clustering in general, please see the clustering
     section of the user manual.</p>

     <h2>Example step-by-step</h2>
     <p><i>To run the example, simply type <code>mvn verify</code> from this directory</i></p>
     <p>In this example, the live server is server 1, and the backup server is server 0</p>
     <p>The connection will initially be created to server1, server 1 will crash, and the client will carry on
     seamlessly on server 0, the backup server.</p>

     <ol>
        <li>Get an initial context for looking up JNDI from server #1.</li>
        <pre class="prettyprint">
           initialContext = getContext(1);
        </pre>

        <li>Look up the JMS resources from JNDI on server #1.</li>
        <pre class="prettyprint">
           Queue queue = (Queue)initialContext.lookup("/queue/exampleQueue");
           ConnectionFactory connectionFactory = (ConnectionFactory)initialContext.lookup("/ConnectionFactory");
        </pre>

        <li>Create a JMS Connection</li>
        <pre class="prettyprint">
           connection = connectionFactory.createConnection();
        </pre>
        
        <li>Create a JMS <em>transacted</em> Session</li>
        <pre class="prettyprint">
           Session session = connection.createSession(true, 0);
        </pre>
        
        <li>Start the connection to ensure delivery occurs</li>
        <pre class="prettyprint">
           connection.start();
        </pre>

        <li>Create a JMS MessageProducer</li>
        <pre class="prettyprint">
           MessageProducer producer = session.createProducer(queue);
        </pre>

        <li>Create a JMS MessageConsumer</li>
        <pre class="prettyprint">
           MessageConsumer consumer = session.createConsumer(queue);
        </pre>

        <li>Send half of the messages, kill the live server and send the remaining messages</li>
        <pre class="prettyprint">
           sendMessages(session, producer, numMessages, true);
        </pre>
        
        <p>When server #1 crashes, the client automatically detects the failure and automatically
            fails over from server #1 to server #0 (in your real program you wouldn't need to sleep).
        </p>
        
        <li>As failover occurred during transaction, the session has been marked for <em>rollback only</em> and commit will fail</li>
        <pre class="prettyprint">
           try
           {
              session.commit();
           } catch (TransactionRolledBackException e)
           {
              System.err.println("transaction has been rolled back: " + e.getMessage());
           }
        </pre>
        
        <li>We resend all the messages</li>
        <pre class="prettyprint">
           sendMessages(session, producer, numMessages, false);
        </pre>

        <li>We commit the session successfully: the messages will be all delivered to the activated backup server</li>
        <pre class="prettyprint">
           session.commit();
        </pre>
        

        <li>We are now transparently reconnected to server #0, the backup server.
            We consume the messages sent before the crash of the live server, commit the session, and check there are no other message on the queue</li>
        <pre class="prettyprint">
        for (int i = 0; i &lt; numMessages; i++)
        {
           TextMessage message0 = (TextMessage)consumer.receive(5000);
           System.out.println("Got message: " + message0.getText());
        }
        session.commit();
        System.out.println("Other message on the server? " + consumer.receive(5000));
        </pre>
        
        <li>And finally, <strong>always</strong> remember to close your 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>

        <pre class="prettyprint">
           finally
           {
              if (connection != null)
              {
                 connection.close();
              }

              if (initialContext != null)
              {
                 initialContext.close();
              }
           }
        </pre>

     </ol>
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