[jboss-jira] [JBoss JIRA] Closed: (JBMESSAGING-355) Remove possibility of delivery race conditions
Ovidiu Feodorov (JIRA)
jira-events at jboss.com
Tue Jan 9 13:57:33 EST 2007
[ http://jira.jboss.com/jira/browse/JBMESSAGING-355?page=all ]
Ovidiu Feodorov closed JBMESSAGING-355.
---------------------------------------
Fix Version/s: 1.2.0.Beta2
(was: 1.2.1)
Resolution: Won't Fix
> Remove possibility of delivery race conditions
> ----------------------------------------------
>
> Key: JBMESSAGING-355
> URL: http://jira.jboss.com/jira/browse/JBMESSAGING-355
> Project: JBoss Messaging
> Issue Type: Task
> Reporter: Tim Fox
> Assigned To: Tim Fox
> Fix For: 1.2.0.Beta2
>
> Attachments: race-condition.log
>
> Original Estimate: 3 days
> Remaining Estimate: 3 days
>
> Currently race conditions can occur on message delivery where the delivery is acknowledged or cancelled before the call to handle has returned.
> In ChannelState we defensively program against this by synchronizing on the returned delivery and by dealing with the situation where the delivery does not exist in the channel state and ignoring.
> See ChannelSupport::deliver() and ChannelState.cancelDelivery.
> This approach has the following problems:
> Complexity of code to maintain and understand.
> Where acks return quickly we are likely to get contention on the lock in ChannelSupport::deliver, thus reducing throughput.
> A much simpler solution enables us to remove the possibility of such race conditions and remove the corresponding lock contention.
> This can be done by adding a confirm() method on Delivery.
> When the receiver receives the message in it's handle() call, before dispatching the message it calls Delivery::confirm. This results in the channel adding the delivery to the channel state. Thus we can be assured that the delivery exists before any acknowledgment or cancellation comes in.
> This is a very simple change.
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