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From "Allen Wittenauer (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MAPREDUCE-2512) wait(5000) and notify() mechanism can be implemented instead of sleep(5000) in reduce task when there are no copies in progress and no new copies to schedule
Date Wed, 18 May 2011 18:34:49 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-2512?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13035559#comment-13035559
] 

Allen Wittenauer commented on MAPREDUCE-2512:
---------------------------------------------

Could this try/catch block be related to the stuck tasks we sometimes see?  What sort of exceptions
are InterruptedException?  

> wait(5000) and notify() mechanism can be implemented instead of sleep(5000) in reduce
task when there are no copies in progress and no new copies to schedule
> -------------------------------------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: MAPREDUCE-2512
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-2512
>             Project: Hadoop Map/Reduce
>          Issue Type: Improvement
>          Components: task
>    Affects Versions: 0.20.2
>            Reporter: Devaraj K
>            Assignee: Devaraj K
>
> {code:title=ReduceTask.java|borderStyle=solid} 
>        try { 
>             if (numInFlight == 0 && numScheduled == 0) { 
>               // we should indicate progress as we don't want TT to think 
>               // we're stuck and kill us 
>               reporter.progress(); 
>               Thread.sleep(5000); 
>             } 
>           } catch (InterruptedException e) { } // IGNORE 
> {code} 
> Here if we have no copies in flight and we can't schedule anything new, it is going to
wait for 5000 millis. Instead of waiting for 5000 millis, this thread can wait with timeout
and GetMapEventsThread can notify it if gets new map completion events earlier than 5000 millis
time. 
>  

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