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From "Bhallamudi Venkata Siva Kamesh (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MAPREDUCE-4013) Reduce task gets stuck when a M/R job is configured to tolerate failures
Date Thu, 15 Mar 2012 14:37:38 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-4013?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13230200#comment-13230200
] 

Bhallamudi Venkata Siva Kamesh commented on MAPREDUCE-4013:
-----------------------------------------------------------

I *think*, the following could be the reason

We are initializing remainingMaps as totalMaps. But if we configure *mapreduce.map.failures.maxpercent*
as some non zero value, job will proceed to run even some maps fail (configured %). However,
decrementing count of remainingMaps, only when the map output copy is sucessful. But even
if a single map fails, it will not be copied and so remainingMaps will be non zero always.


{code:title=ShuffleScheduler.java|borderStyle=solid}
 if (--remainingMaps == 0) {
        notifyAll();
 }
{code}
                
> Reduce task gets stuck when a M/R job is configured to tolerate failures
> ------------------------------------------------------------------------
>
>                 Key: MAPREDUCE-4013
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-4013
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>          Components: mrv2
>    Affects Versions: 0.23.2
>            Reporter: Amar Kamat
>            Priority: Blocker
>              Labels: shuffle
>             Fix For: 0.24.0
>
>
> When a M/R job is configured to run with some tolerance to task failures (via mapreduce.map.failures.maxpercent),
then the reduce task of that job gets stuck in the shuffle phase. 

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