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From "Gary Tully (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (AMQ-4157) KahaDBTransactionStore.removeAyncMessage may cancel addMessage when in transaction leading to unpersisted messages
Date Mon, 11 Feb 2013 22:43:13 GMT

     [ https://issues.apache.org/jira/browse/AMQ-4157?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Gary Tully updated AMQ-4157:
----------------------------

    Fix Version/s:     (was: 5.8.0)
                   5.9.0
    
> KahaDBTransactionStore.removeAyncMessage may cancel addMessage when in transaction leading
to unpersisted messages
> ------------------------------------------------------------------------------------------------------------------
>
>                 Key: AMQ-4157
>                 URL: https://issues.apache.org/jira/browse/AMQ-4157
>             Project: ActiveMQ
>          Issue Type: Bug
>          Components: Message Store
>    Affects Versions: 5.7.0
>         Environment: linux 64-bit, kahadb, persisted messages, cached dest, transacted
>            Reporter: Martin Serrano
>            Assignee: Gary Tully
>            Priority: Blocker
>             Fix For: 5.9.0
>
>         Attachments: org.apache.activemq.bugs.AMQ4157Test-output.txt
>
>
> This was very difficult to track down.  It rarely occurs because a certain set of events
must be occurring to trigger the bug.   I have marked it a Blocker because when it does occur,
it is silent and leads to a message not being persisted in the MessageStore.
> *Description*
> The crux of the bug is that when a rollback on a session occurs, the resulting MessageAck
can overlap with the async store of the message in the KahaDB.   When this occurs, the message
is never persisted.  Additionally, the resultant {{CancellationException}} is ignored in o.a.a.broker.region.Queue:796.
  The steps:
> # a StoreQueueTask is created to add a message X.  this is put on the async task queue
> # meanwhile this message is dispatched via a prefetch subscription to a transacted consumer.
> # the transacted consumer calls session.rollback
> # this leads to acknowledgement of the dispatched message
> # as a result {{destination.removeAsyncMessage()}} is called
> # if the original add has not yet executed then it will be cancelled leading to the message
never being persisted!  (occurs at KahaDBStore:401)
> # the Queue.send method uses the result future to make sure the persist happens in the
store, but it ignores cancellation, so this can lead execution control to return to the sender
when no persistence has occurred without an error.
> I have not been able to reproduce this in a small activemq-only test.  But I can reproduce
it in my environment.  
> *Proposed Solutions*
> I'm really unsure of the solution here.  Should {{KahaDBStore.removeAsyncMessage}} (line
393) check the context and only cancel tasks if it is not in a transaction context?  But what
would that mean in the log?  Would there be a removeMessage prior to the addMessage?
> *Workaround*
> * turn off caching for the destination (see [dest policies|http://activemq.apache.org/per-destination-policies.html]).
 this will cause messages to be added synchronously so they will not be subject to the async
cancellation

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