WSO2 2.2.0 Message Broker中的消息重试和死信队列

Question

We are evaluating the WSO2 stack and in particular the Message Broker v 2.2.0 and are not able to make the message retry limit work.

According to this documentation page, once the client has rejected a message 10 times it will be removed from the queue and placed on the dead letter queue.

https://docs.wso2.com/display/MB220/Maximum+Delivery+Attempts

Out definition of rejection is either:
a) Not sending acknowledgement in the case of using Session.CLIENT_ACKNOWLEDGE or
b) Rolling back the transaction in the case of using a transacted session.

Using the WSO2 example client code we are unable to observe this behaviour using any combination of client acknowledgement modes or induced failures. The message remains active in the queue and can be taken from it any number of times. Acknowledging it or committing the session removes it from the queue as you would expect.

Can anyone confirm if this feature actually works and if so, show us what a client has to do to trigger it. We have been testing using the WSO2 provided sample client code and an unmodified out-of-the-box server config:

https://docs.wso2.com/display/MB220/Sending+and+Receiving+Messages+Using+Queues

Any help would be appreciated as we are unable to continue with WSO2 without understanding exactly how this aspect of the system works.

Answer 1

This feature is working as expected. In order to test that you need to do some modification to the provided receiver client in the sample code.

1. Add the given system property
2. Change the abknlowdgment mode to CLIENT_ACK
3. Get the message for 10 times without sending the ACK to server

With these changes you can cater your requirement.

Here I am posting the modified method in the QueueReceiver class

public void receiveMessages() throws NamingException, JMSException {
    Properties properties = new Properties();
    System.setProperty("AndesAckWaitTimeOut", "30000");
    properties.put(Context.INITIAL_CONTEXT_FACTORY, QPID_ICF);
    properties.put(CF_NAME_PREFIX + CF_NAME, getTCPConnectionURL(userName, password));
    System.out.println("getTCPConnectionURL(userName,password) = " + getTCPConnectionURL(userName, password));
    InitialContext ctx = new InitialContext(properties);
    // Lookup connection factory
    QueueConnectionFactory connFactory = (QueueConnectionFactory) ctx.lookup(CF_NAME);
    QueueConnection queueConnection = connFactory.createQueueConnection();
    queueConnection.start();
    QueueSession queueSession =
            queueConnection.createQueueSession(false, QueueSession.CLIENT_ACKNOWLEDGE);
    //Receive message
    Queue queue =  queueSession.createQueue(queueName);
    MessageConsumer queueReceiver = queueSession.createConsumer(queue);
    int count =0;
    while (count < 12) {
        TextMessage message = (TextMessage) queueReceiver.receive();
        System.out.println("Got message ==>" + message.getText());
        count++;
    }
    queueReceiver.close();
    queueSession.close();
    queueConnection.stop();
    queueConnection.close();
}

Please note that this modification is done for just proofing that the feature is working.