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From "Todd Lipcon (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 Mon, 06 Jun 2011 21:02:59 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-2512?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13045101#comment-13045101
] 

Todd Lipcon commented on MAPREDUCE-2512:
----------------------------------------

As this is an optimization, you should prepare a patch against trunk if the issue exists there.
We don't generally put optimizations backward into prior releases.

> 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
>             Fix For: 0.20.4
>
>         Attachments: MAPREDUCE-2512.patch
>
>
> {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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