197 lines
11 KiB
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197 lines
11 KiB
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<html>
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<head>
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<title>ActiveMQ Message Counter 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 Message Counter Example</h1>
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<p>This example shows you how to use message counters to obtain message information for a JMS queue.</p>
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<p>The example will show how to configure sampling of message counters.<br />
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We will produce and consume 1 message from a queue. Interleaved with the JMS operation, we will retrieve the queue's message counters
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at different times to display the metrics on the queue.
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</p>
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<h2>Example setup</h2>
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<p>Message counter is configured in the server configuration file <a href="server0/activemq-configuration.xml">activemq-configuration.xml</a>:</p>
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<pre class="prettyprint">
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<code><message-counter-enabled>true</message-counter-enabled>
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<message-counter-sample-period>2000</message-counter-sample-period>
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<message-counter-max-day-history>2</message-counter-max-day-history></code>
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</pre>
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<p>By default, Message counter is not enabled (for performance reason). To enable them, set <code>message-counter-enabled</code> to <code>true</code>.<br />
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Queues are sampled every 10 seconds by default. For this example we will reduce it to 2 seconds by setting <code>message-counter-sample-period</code> to <code>2000</code>.<br />
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ActiveMQ holds in memory the message counters' history for a maximum number of days (10 by default). We can change the number of days the history is kept by setting
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the <code>message-counter-max-day-history</code> parameter.</p>
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<p>The sample period and the max day history parameters have an small impact on the performance of ActiveMQ (the resources taken to sample a queue are not available to the system's
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normal use). You should set these parameters accordingly to the use and throughput of your messages.</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>First we need to get an initial context so we can look-up the JMS connection factory and destination objects from JNDI. This initial context will get it's properties from the <code>client-jndi.properties</code> file in the directory <code>../common/config</code></li>
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<pre class="prettyprint">
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<code>InitialContext initialContext = getContext();</code>
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</pre>
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<li>We look up the JMS queue object from JNDI</li>
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<pre class="prettyprint">
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<code>Queue queue = (Queue) initialContext.lookup("/queue/exampleQueue");</code>
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</pre>
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<li>We look up the JMS connection factory object from JNDI</li>
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<pre class="prettyprint">
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<code>ConnectionFactory cf = (ConnectionFactory) initialContext.lookup("/ConnectionFactory");</code>
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</pre>
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<li>We create a JMS connection, session and producer for the queue</li>
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<pre class="prettyprint">
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<code> connection = cf.createQueueConnection();
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QueueSession session = connection.createQueueSession(false, Session.AUTO_ACKNOWLEDGE);
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MessageProducer producer = session.createProducer(queue);</code>
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</pre>
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<li>We create and send a JMS text message</li>
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<pre class="prettyprint">
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<code>TextMessage message = session.createTextMessage("This is a text message");
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producer.send(message);
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System.out.println("Sent message: " + message.getText());</code>
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</pre>
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<li>We will now sleep a little bit to be sure the queue is sample. Since we have configure the sample period to be 2 seconds,
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we will sleep for 3 seconds to be sure that a sample is taken</li>
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<pre class="prettyprint">
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<code>System.out.println("Sleep a little bit to have the queue sampled...");
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Thread.sleep(3000);</code>
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</pre>
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<p>We now need to retrieve the message counters. They're available from the JMS Queue management resource. In this example, we
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will retrieve them using JMX (see the <a href="../jmx/readme.html">JMX example</a> for a more complete description). You can also use JMS message to retrieve them (see the <a href="../management/readme.html">Management example</a> to
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learn about managing ActiveMQ using JMS messages).</p>
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<li>We retrieve the JMX MBean used to manage the JMS queue</li>
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<pre class="prettyprint">
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<code>ObjectName on = ObjectNameBuilder.DEFAULT.getJMSQueueObjectName(queue.getQueueName());
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JMXConnector connector = JMXConnectorFactory.connect(new JMXServiceURL(JMX_URL), new HashMap());
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MBeanServerConnection mbsc = connector.getMBeanServerConnection();
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JMSQueueControl queueControl = (JMSQueueControl)MBeanServerInvocationHandler.newProxyInstance(mbsc,
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on,
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JMSQueueControl.class,
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false);</code>
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</pre>
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<li>We retrieve the message counter and display them. MessageCounters are retrieved as <code>JSON Strings</code> for portability reason (whether
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JMX is used for management or JMS messages). To make it simpler to use them in the code, there is a <code>MessageCounterInfo</code> data structure.</li>
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<pre class="prettyprint">
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<code>String counters = queueControl.listMessageCounter();
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MessageCounterInfo messageCounter = MessageCounterInfo.fromJSON(counters);</code>>
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</pre>
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<li>We display the message counters</li>
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<pre class="prettyprint">
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<code>displayMessageCounter(messageCounter);</code>
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</pre>
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<p>The message counter contains a variety of metrics on the queue which is sampled (total messages added to the queue, current depth of the queue, deltas since the last sample, timestamp
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of the last message added, timestamp of the last sample, etc.)</p>
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<pre class="prettyprint">
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<code>
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private void displayMessageCounter(MessageCounterInfo counter)
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{
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System.out.format("%s (sample updated at %s)\n", counter.getName(), counter.getUdpateTimestamp());
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System.out.format(" %s message(s) added to the queue (since last sample: %s)\n", counter.getCount(),
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counter.getCountDelta());
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System.out.format(" %s message(s) in the queue (since last sample: %s)\n", counter.getDepth(),
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counter.getDepthDelta());
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System.out.format(" last message added at %s\n\n", counter.getLastAddTimestamp());
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}</code>
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</pre>
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<li>We sleep again to have the queue sampled</li>
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<pre class="prettyprint">
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<code>System.out.println("Sleep a little bit again...");
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Thread.sleep(3000);</code>
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</pre>
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<li>We list the message counters again</li>
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<pre class="prettyprint">
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<code>counters = queueControl.listMessageCounter();
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messageCounter = MessageCounterInfo.fromJSON(counters);
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displayMessageCounter(messageCounter);</code>
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</pre>
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<p>We will now consume a message from the queue before listing a last time the message counters</p>
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<li>We create a consumer for the queue</li>
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<pre class="prettyprint">
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<code>MessageConsumer consumer = session.createConsumer(queue);</code>
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</pre>
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<li>We start the connection to receive messages on the consumer</li>
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<pre class="prettyprint">
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<code>connection.start();</code>
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</pre>
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<li>We receive a message from the queue</li>
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<pre class="prettyprint">
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<code>TextMessage messageReceived = (TextMessage)consumer.receive(5000);
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System.out.format("Received message: %s\n\n", messageReceived.getText());</code>
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</pre>
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<li>We sleep one last time to have the queue sampled</li>
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<pre class="prettyprint">
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<code>System.out.println("Sleep a little bit one last time...");
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Thread.sleep(3000);</code>
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</pre>
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<li>We list the message counters a final time (this time with no message in the queue)</li>
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<pre class="prettyprint">
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<code>counters = queueControl.listMessageCounter();
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messageCounter = MessageCounterInfo.fromJSON(counters);
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displayMessageCounter(messageCounter);</code>
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</pre>
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</p>
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<li>And finally, <b>always</b> remember to close your JMS connections and 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>finally
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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 (connection != null)
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{
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connection.close();
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}
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}</code>
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</pre>
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</ol>
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<li>User Manual's <a href="../../../docs/user-manual/en/html_single/index.html#management.message-counters">Message Counters chapter</a></li>
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<li><a href="../../../docs/api/org/jboss/messaging/core/management/MessageCounterInfo.html">MessageCounterInfo</a> is a helper class used
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to create a MessageCounterInfo object from the JSON String which represents message counters</li>
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</body>
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</html>
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