[jboss-jira] [JBoss JIRA] Commented: (JGRP-540) Multiplexer: ordering issue

Tue Jun 26 11:12:58 EDT 2007

    [ http://jira.jboss.com/jira/browse/JGRP-540?page=comments#action_12366863 ] 

Vladimir Blagojevic commented on JGRP-540:
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An easier way to reproduce this problem very frequently is to remove sleep (Util.sleepRandom(200)) in the receiver used in MultiplexerTest#testOrdering test method. Test fails for me every time after the sleep is removed. 

After further investigation it indeed seems that thread pool is indeed the culprit and more specifically the problem is I believe in SynchronousQueue hand off mechanism in thread pool. This hand off mechanism is inherently by its own design violating FIFO order and should be replaced by LinkedBlockingQueue. After the change testOrdering test was passing consistently. However, that introduced failures in MultiplexerConcurrentTest. I then realized that in order to have concurrency we need for MultiplexerConcurrentTest to pass and ordering we need to use LinkedBlockingQueue but we also need to increase number of core threads in thread pool. After this change all tests were passing consistently.  

> Multiplexer: ordering issue
> ---------------------------
>
>                 Key: JGRP-540
>                 URL: http://jira.jboss.com/jira/browse/JGRP-540
>             Project: JGroups
>          Issue Type: Bug
>            Reporter: Bela Ban
>         Assigned To: Vladimir Blagojevic
>             Fix For: 2.5
>
>
> Sometimes messages from the same sender are not delivered in the correct order, the test that shows this (happens infrequently) is MultiplexerTest.testOrdering(). 
> When disabling the Multiplexer thread pool (-Djgroups.mux.enabled=false), everything works fine, so I suspect this is a thread pool issue in the Multiplexer (FIFOMessageQueue).

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