3 Replies Latest reply on Jul 12, 2005 12:36 PM by Chris

    How to make sure a message is delivered no more than once

    Chris Newbie

      I have a queue set up with two clients listening to the queue. (non-persisent, auto acknowlege, JBoss 4.0.2) both clients are getting all of the messages sent to the queue. Essentially my queue is behaving in pub/sub.

      how do I unsure that a message in a queue is delivered no more than once?

        • 1. Re: How to make sure a message is delivered no more than onc
          Darran Lofthouse Master

          Are you sure that you are using a queue and not a topic?

          • 2. Re: How to make sure a message is delivered no more than onc
            Chris Newbie

            yes, it is a Queue. I am a little suprised at this problem, although I have never done a Queue before usually always dealing with topics.

            I need to distribute a process. a queue with multiple consumers seemed the perfect answer, because each task passed along could get grabbed by exactly one consumer.


             <mbean code="org.jboss.mq.server.jmx.Queue"
             name="jboss.mq.destination:service=Queue,name=uncategorizedpages">
             <depends optional-attribute-name="DestinationManager">jboss.mq:service=DestinationManager</depends>
             </mbean>
            


            The code uses Queue in the usual way:

             Context ctx = new InitialContext(config);
             QueueConnectionFactory queueFactory = (QueueConnectionFactory) ctx.lookup("ConnectionFactory");
             Destination queueDestination = (Destination) ctx.lookup(unitQueueName);
            
             QueueConnection queueConnection = (QueueConnection) queueFactory.createConnection(unitQueueUser, unitPagesQueuePass);
             Session queueSession = queueConnection.createQueueSession(false, Session.AUTO_ACKNOWLEDGE);
            
             List<UnitVO> batch = loadBatch(0);
            
            
             // for each page in the batch
             for (UnitVO unit : batch)
             {
             MessageProducer producer = queueSession.createProducer(queueDestination);
             producer.setDeliveryMode(DeliveryMode.NON_PERSISTENT);
             ObjectMessage msg = queueSession.createObjectMessage(page);
             producer.send(msg);
             producer.close();
            
             }
             queueSession.close();
             queueConnection.close();
            


             Context ctx = new InitialContext(this.config);
             QueueConnectionFactory queueConnnectionFactory = (QueueConnectionFactory) ctx.lookup(connectionFactoryJNDIName);
             QueueConnection queueConnection = queueConnnectionFactory.createQueueConnection(unitQueueUser, unitQueuePass);
             QueueSession unitSession =
             queueConnection.createQueueSession(false, Session.AUTO_ACKNOWLEDGE);
             Queue unitQueue =
             (Queue) ctx.lookup(unitQueueName);
             QueueReceiver receiver =
             unitSession.createReceiver(unitQueue);
             queueConnection.start();
            
            
             // until we are told to stop
             while (!shutdown)
             {
             Message msg = receiver.receive(1000);
            
             if (msg != null && msg instanceof ObjectMessage)
             {
             UnitVO page = (UnitVO) ((ObjectMessage) msg).getObject();
             System.out.println(unit.getId());
             }
             else {
             shutdown=true;
             }
             }
            


            • 3. Re: How to make sure a message is delivered no more than onc
              Chris Newbie

              As I experiment with this more I find that it is a time delay in removing the message from the queue.

              If i sleep the consumer thread for a small random interval it helps break things up. But I still get duplicates on each consumer.