Message peek in IBM MQ

Question

In MSMQ there is a functionality that lets users to peek at a message without actually consuming it. i.e. I peek at the next message in a Queue based on MessageID. If I am not interested in the message I can put the message back into the Queue (i.e. unacknowledged are added back to the Queue and the messageID is maintained).

Similar functionality also exists in RabbitMQ. However in RabbitMQ its not done in a clean way. You can simulate peeking messages by taking the message off the queue and then not sending an acknowledgement so RabbitMQ will then add that message back to the queue. However I read that RabbitMQ can reorder the messages and increment message IDs when unacknowledged messages are re-added to the queue.

Has anyone encountered this problem before.

Also does any one know if IBM MQ supports this behaviour/functionality of peek and seek?

regards D

What is peek and seek? The functionality you're looking for in IBM MQ for having a 'peek' at a message is referred to as a BROWSE. — Tim McCormick
You should be able to use javax.jms.Session.createBrowser(javax.jms.Queue) to scan the queue contents then use javax.jms.Session.createConsumer(Destination destination, java.lang.String messageSelector) to consume the desired message found while browsing. — Stavr00

Shashi Shashi · Accepted Answer · 2015-05-22T15:18:20

IBM MQ provides a way to browse messages without removing them from queue. You can start browsing messages from the beginning and iterate through all messages in a queue. You can also browse a specific message using MessageId or CorrelationId.

Here is snippet in C# for browsing messages in a queue.

    /// <summary>
    /// Browse messages in a queue
    /// </summary>
    private void BrowseMessages()
    {
        MQQueueManager qm = null;
        MQQueue queueGet = null;
        Hashtable mqProps = null;

        try
        {
            mqProps = new Hashtable();
            // Setup properties for connection
            mqProps.Add(MQC.TRANSPORT_PROPERTY, MQC.TRANSPORT_MQSERIES_MANAGED);
            mqProps.Add(MQC.HOST_NAME_PROPERTY, "localhost");
            mqProps.Add(MQC.PORT_PROPERTY, 1414);
            mqProps.Add(MQC.CHANNEL_PROPERTY, "QM.SVRCONN");

            // Open connection to queue manager
            qm = new MQQueueManager("QM", mqProps);

            // Open queue for browsing
            queueGet = qm.AccessQueue("Q1", MQC.MQOO_BROWSE | MQC.MQOO_FAIL_IF_QUIESCING);

            // In a loop browse all messages till we reach end of queue
            while (true)
            {
                try
                {
                    // Need to create objects everytime
                    MQMessage msg = new MQMessage();
                    MQGetMessageOptions gmo = new MQGetMessageOptions();

                    // Use browse next option to start browsing
                    gmo.Options = MQC.MQGMO_BROWSE_NEXT;
                    queueGet.Get(msg, gmo);
                    Console.WriteLine(msg.ReadString(msg.MessageLength));
                }
                catch (MQException mqex)
                {
                    // When there are no more messages to browse, the Get call
                    // will throw MQException with reason code MQC.MQRC_NO_MSG_AVAILABLE.
                    // But here we close the queue and break out of loop for all exceptions
                    queueGet.Close();
                    break;
                }
            }
            qm.Disconnect();
        }
        catch (MQException mqex)
        {
            Console.WriteLine(mqex);
        }
    }

Message peek in IBM MQ

2 Answers