[jboss-jira] [JBoss JIRA] Commented: (JGRP-500) FLUSH bug

Thu May 10 14:20:54 EDT 2007

    [ http://jira.jboss.com/jira/browse/JGRP-500?page=comments#action_12362002 ] 

Vladimir Blagojevic commented on JGRP-500:
------------------------------------------

Maybe we do not have the same understanding of block callback! We designed callback block as simply a notification to application level that channel will be blocked for flush. This callback *should not* potentially block indefinitely like it is the case in your example. 

Yes I admit that result are indeterminate because this example is a clear misuse of block contract. 

> FLUSH bug
> ---------
>
>                 Key: JGRP-500
>                 URL: http://jira.jboss.com/jira/browse/JGRP-500
>             Project: JGroups
>          Issue Type: Bug
>            Reporter: Bela Ban
>         Assigned To: Vladimir Blagojevic
>             Fix For: 2.5
>
>         Attachments: JGroupsFlushBug.java
>
>
> [reported by Michael Newcomb]
> Here is a test program to demonstrate the bug.
> Start 2 instances of the JGroupsFlushBug app.
> In window 1, type: 'sleep 5'
> This will send a message to both apps and they will both sleep for 5
> seconds. The app that issued the sleep command will wait until both have
> slept 5 seconds and then return.
> When the sleep command is issued, it grabs a lock on a Semaphore. This
> lock is released when it receives a response to the sleep command.
> When a block() is called it grabs the lock on the Semaphore so that no
> more sleep commands can execute. Likewise, if a sleep command is
> executing, block() will wait until it completes and then grab the lock.
> At least that is what is supposed to happen ;)
> Now, in window 1, type: 'sleep 10'
> Quickly change to window 2 and type: 'flush'
> You will see that the flush does not complete correctly. You will see
> the flush timeout and then repeatedly tries to start the flush again.
> Even when the sleep completes, the retries fail...
> Can someone confirm my results?
> Thanks,
> Michael

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