[jboss-jira] [JBoss JIRA] Commented: (JBMESSAGING-1245) Message delivery freezes with default values of prefetchSize and slowConsumers

[Tim Fox (JIRA)]

    [ http://jira.jboss.com/jira/browse/JBMESSAGING-1245?page=comments#action_12402117 ] 
            
Tim Fox commented on JBMESSAGING-1245:
--------------------------------------

By inspection of the code I believe I can potential for a race condition which could cause the observed problem.

In ServerConsumerEndpoint::handle()

if (sendCount == num)
         {
         	
         	//if change rate gets set to zero here then would get stuck!! ****
         	
            clientAccepting = false;
            
            firstTime = false;
         }    

If a call to changeRate() comes in at line ****, then it is possible that sendCount gets set to zero, and clientAccepting remains false, which would cause consumers to become stuck

Workarounds for now woud be to set prefetchSize to a very large value so that TCP flow control takes effect - although this may not be ideal.

Proper fix is to make sure those actions are properly synchronized.

> Message delivery freezes with default values of prefetchSize and slowConsumers
> ------------------------------------------------------------------------------
>
>                 Key: JBMESSAGING-1245
>                 URL: http://jira.jboss.com/jira/browse/JBMESSAGING-1245
>             Project: JBoss Messaging
>          Issue Type: Bug
>            Reporter: Tim Fox
>         Assigned To: Tim Fox
>             Fix For: 1.4.0.SP3.CP02, 1.4.1.beta2
>
>
> Message delivery seems to freeze under some circumstances with default values of prefetchSize and slowConsumers.
> Increasing the prefetchSize to 1000 seems to workaround the problem.
> Waiting on customer to provide instructions for replication.

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