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https://issues.apache.org/jira/browse/QPID-2120?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Martin Ritchie updated QPID-2120:
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Status: Ready To Review (was: In Progress)
> [race condition] asynchronous delivery and message rejection can result in
> out of order message deilvery
> --------------------------------------------------------------------------------------------------------
>
> Key: QPID-2120
> URL: https://issues.apache.org/jira/browse/QPID-2120
> Project: Qpid
> Issue Type: Bug
> Components: Java Broker
> Reporter: Martin Ritchie
> Assignee: Martin Ritchie
> Priority: Blocker
> Fix For: 0.6
>
>
> The recent fixes for rollback QPID-2116 and QPID-1871 highlighted a race
> condition in the broker.
> When messages are rejected asynchronous delivery is started to see if any
> current consumer wants the message. The 0-8 java client rejects messasges in
> the following order: Prefetch then Delivered. As a result the
> RollbackOrderTest#testOnMessage that receives one message then rolls back can
> receive the second message ahead of the first message.
> This was possible because we retrieved the node (getLastSeenNode) then later
> checked if we were suspended. So with a suitable sleep in the client between
> rollback and the restarting of the Channel Flow state (=true) the problem can
> be seen to vanish. What was occuring was the async process retreived the last
> seen (message 2) the last Reject is processed releasing Message 1. The Async
> process is still attempting delivery of Message 2 when the Flow=true arrives
> and so it can deliver Messasge 2.
> The fix is to ensure that a suspended client cannot enter a path where it
> could deliver a message.
> This is safe as all Rejects will be full processed before the Flow=true is
> sent so any process attempting to getLastSeenNode() must do so AFTER a
> sub.isSuspended() check.
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