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From "Alexis Kinsella (JIRA)" <j...@apache.org>
Subject [jira] Created: (AMQ-1730) Bad use of Jms field JMSXDeliveryCount. Related to RedeliveryCount and message prefetch
Date Thu, 15 May 2008 13:40:43 GMT
Bad use of Jms field JMSXDeliveryCount. Related to RedeliveryCount and message prefetch 
----------------------------------------------------------------------------------------

                 Key: AMQ-1730
                 URL: https://issues.apache.org/activemq/browse/AMQ-1730
             Project: ActiveMQ
          Issue Type: Bug
          Components: Broker
    Affects Versions: 5.1.0, 5.0.0
            Reporter: Alexis Kinsella


JMSXDeliveryCount  has to be incremented only on transactional delivery failure ( RuntimeException
on processing message, ... ).

JMSXDeliveryCount  is actualy used in correlation with Message.java field: 'redeliveryCounter'.

But RedeliveryCounter  field is used to be incremented each time the message is preteched
or sent to a consumer => It does not mean that message has been processed by business in
transaction with a failure. It just has been prefetched by consumer ou subscriber. 
A 'not consumed message' can be give back to the broker when the consumer is closed by user,
because it has been prefetched but not really consumed!

It does not match the meaning of the JMS field JMSXDeliveryCount  :
"If a failure occurs within transactional processing then the JMSXDeliveryCount is incremented".


JMSXDeliveryCount  field only has to be incremented on rollback (isn't it? ). This is why
Message.redeliveryCount can not be used. Or the behavour of field Message.redeliveryCount
has to be changed.

You can either :
* create a new counter on message incremented only on rollback, or
* modify classes : PrefetchSubscription.java and Queue.java to remove redeliveryCount increment
and increment it only on rollback.


* PrefetchSubscription.java:

                    if (inAckRange) {
//                        node.incrementRedeliveryCounter();
                        if (ack.getLastMessageId().equals(messageId)) {
                            destination = node.getRegionDestination();
                            callDispatchMatched = true;
                            break;
                        }
                    }



* Queue.java:

                for (MessageReference ref : sub.remove(context, this)) {
                    QueueMessageReference qmr = (QueueMessageReference)ref;
//                    qmr.incrementRedeliveryCounter();
                    if( qmr.getLockOwner()==sub ) {
                        qmr.unlock();
//                        if (!qmr.isDropped() && !qmr.isAcked()) {
//                        	qmr.incrementRedeliveryCounter();
//                        }
                    }
                    list.add(qmr);
                }


BTW, In this code it seems there is a second bug, in case of  test "qmr.getLockOwner()==sub"
is true qmr is incremented a second time ?! Is it right ?



The result of this problem is the following: 

With Spring and DefaultMessageListenerContainer, a message is consumed one by one. This is
why a message prefteched many times, on first real consuming has a JMSXDeliveryCount  with
high value not reflecting the reality.

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