activemq-artemis/examples/jms/consumer-rate-limit
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  <head>
    <title>ActiveMQ JMS Message Consumer Rate Limiting</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 Message Consumer Rate Limiting</h1>

     <p>With ActiveMQ you can specify a maximum consume rate at which a JMS MessageConsumer will consume messages.
     This can be specified when creating or deploying the connection factory. See <code>activemq-jms.xml</code></p>
     <p>If this value is specified then ActiveMQ will ensure that messages are never consumed at a rate higher than
     the specified rate. This is a form of consumer <i>throttling</i>.</p>     
     <h2>Example step-by-step</h2>
     <p>In this example we specify a <code>consumer-max-rate</code> of <code>10</code> messages per second in the <code>activemq-jms.xml</code>
     file when deploying the connection factory:</p>
     <pre class="prettyprint">
     <code>
   &lt;connection-factory name="ConnectionFactory"&gt;
      &lt;connector-ref connector-name="netty-connector"/&gt;
      &lt;entries&gt;
         &lt;entry name="ConnectionFactory"/&gt;       
      &lt;/entries&gt;
      
      &lt;!-- We limit consumers created on this connection factory to consume messages at a maximum rate
      of 10 messages per sec --&gt;
      &lt;consumer-max-rate&gt;50&lt;/producer-max-rate&gt;
      
   &lt;/connection-factory&gt;
     </code>
     </pre>
     <p>We then simply consume as many messages as we can in 10 seconds and note how many messages are actually consumed.</p>
     <p>We note that the number of messages consumed per second never exceeds the specified value of <code>10</code> messages per second.</p>

     <p><i>To run the example, simply type <code>mvn verify</code> from this directory</i></p>

     <ol>
        <li>Create an initial context to perform the JNDI lookup.</li>
        <pre class="prettyprint">
           <code>initialContext = getContext(0);</code>
        </pre>

        <li>Perfom a lookup on the queue</li>
        <pre class="prettyprint">
           <code>Queue queue = (Queue)initialContext.lookup("/queue/exampleQueue");</code>
        </pre>

        <li>Perform a lookup on the Connection Factory</li>
        <pre class="prettyprint">
           <code>ConnectionFactory cf = (ConnectionFactory)initialContext.lookup("/ConnectionFactory");</code>
        </pre>

        <li>Create a JMS Connection</li>
        <pre class="prettyprint">
           <code>connection = cf.createConnection();</code>
        </pre>

        <li>Create a JMS Session</li>
        <pre class="prettyprint">
           <code>Session session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);</code>
        </pre>

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

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

        <li>Send a bunch of messages</li>
        <pre class="prettyprint">
           <code>
     final int numMessages = 150;
         
     for (int i = 0; i < numMessages; i++)
     {
        TextMessage message = session.createTextMessage("This is text message: " + i);

        producer.send(message);
     }           
           </code>
        </pre>
        
        <li>Consume as many messages as we can in 10 seconds</li>
        
        <pre class="prettyprint">
           <code>
   final long duration = 10000;

   int i = 0;

   long start = System.currentTimeMillis();

   while (System.currentTimeMillis() - start <= duration)
   {
      TextMessage message = (TextMessage)consumer.receive(2000);

      if (message == null)
      {
         return false;
      }
      
      i++;
   }

   long end = System.currentTimeMillis();

   double rate = 1000 * (double)i / (end - start);

   System.out.println("We consumed " + i + " messages in " + (end - start) + " milliseconds");

   System.out.println("Actual consume rate was " + rate + " messages per second");           
           </code>
        </pre>
        
        <li>This should produce output something like:</li>
        
        <pre class="prettyprint">
           <code>
    [java] Sent messages
    [java] Will now try and consume as many as we can in 10 seconds ...
    [java] We consumed 100 messages in 10001 milliseconds
    [java] Actual consume rate was 9.99900009999 messages per second
                 
           </code>
        </pre>

        <li>Be sure to close our resources!</li>

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



     </ol>
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