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From "Lorenz Quack (JIRA)" <j...@apache.org>
Subject [jira] [Created] (QPID-6700) Out of order delivery of messages caused by out of order message rejection
Date Tue, 18 Aug 2015 15:51:45 GMT
Lorenz Quack created QPID-6700:
----------------------------------

             Summary: Out of order delivery of messages caused by out of order message rejection
                 Key: QPID-6700
                 URL: https://issues.apache.org/jira/browse/QPID-6700
             Project: Qpid
          Issue Type: Bug
          Components: Java Broker
            Reporter: Lorenz Quack


Analysis of a failing systest (MessageConsumerCloseTest#testPrefetchedMessagesReleasedOnConsumerClose)
revealed the following an issue where during consumer close prefetched messages can be rejected
out of order resulting in out of order delivery to another consumer.

* The main thread calls consumer.close which locks the messageDeliveryLock before sending
Cancel and waiting synchronously for a CancelOk.
* During that time the Dispatcher pops a message from the pre-dispatch queue and calls dispatchMessage
which will spin in a loop trying to lock the messageDeliveryLock. (Delivery Tag 25 in the
attached log)
* Once the CancelOk arrives on the IO-Recv thread the BasicCancelOkMethodHandler calls session.confirmConsumerCancelled
which ends up rejecting the remaining messages on the pre-dispatch queue. (Delivery Tag 26
in the attached log)
* Only after this happens is the messageDeliveryLock released by the main thread so that the
dispatcher can reject the message it has popped from the pre-dispatch queue and was in the
process of dispatching. (Delivery Tag 25)

Possible fixes:
* acquire dispatcherLock on consumer#close, session#close, and connection#close or
* be more conservative where we acquire the messageDeliveryLock in the dispatcher (hold it
while we fetch message from pre-dispatch queue and handle it). Taking this approach could
possibly open up the possiblity of merging dispatcherLock and messageDeliveryLock.




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