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From "Alan Conway (JIRA)" <j...@apache.org>
Subject [jira] [Resolved] (QPID-4402) HA QMF events can be out of order.
Date Wed, 31 Oct 2012 21:21:12 GMT

     [ https://issues.apache.org/jira/browse/QPID-4402?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Alan Conway resolved QPID-4402.

    Resolution: Duplicate

Duplicate of QPID-4394
> HA QMF events can be out of order.
> ----------------------------------
>                 Key: QPID-4402
>                 URL: https://issues.apache.org/jira/browse/QPID-4402
>             Project: Qpid
>          Issue Type: Bug
>          Components: C++ Clustering
>    Affects Versions: 0.18
>            Reporter: Alan Conway
>            Assignee: Alan Conway
> With the new replication-based clustering in 0.18 MRG-M, it is possible for the replication
to hang if the QMF events arrive in the wrong order.  I am running the following test that
generates the hanging:
> - Start a client with 2 threads
> - Each thread creates its own Connection, Session, and a Receiver using the address "someQueue;
{create:always, node: {x-declare: {auto-delete:True}}}"
> - Run a loop like this (pseudocode):
> while(receiver.get(message)) {
>   // do stuff
>   if at least 5 seconds have passed {
>     connection.close();
>     reconnectAndRecreateReceiver();
>     receiver.setCapacity(1000);
>   }
> }
> During this loop, the 2 threads will disconnect and reconnect every 5 seconds.  When
connecting, 1 of them will create a queue.  When disconnecting, the queue will be deleted.
 At some point, the queue creation event will possibly arrive at the backup broker before
the queue deletion event (i.e. in the wrong order) because there is no lock that governs when
queue creation/deletion events are emitted.  When this happens, the backup broker doesn't
subscribe to the primary to replicate the queue in question, and things hang.
> This is not strictly a HA problem, any QMF client may receive incorrectly ordered events.
It comes up in the HA context because QMF events are used heavily by HA for replication.

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