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https://issues.apache.org/jira/browse/MAPREDUCE-5817?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14524910#comment-14524910
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Hadoop QA commented on MAPREDUCE-5817:
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| (x) *{color:red}-1 overall{color}* |
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|| Vote || Subsystem || Runtime || Comment ||
| {color:red}-1{color} | patch | 0m 0s | The patch command could not apply
the patch during dryrun. |
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|| Subsystem || Report/Notes ||
| Patch URL |
http://issues.apache.org/jira/secure/attachment/12638107/mapreduce-5817.patch |
| Optional Tests | javadoc javac unit findbugs checkstyle |
| git revision | trunk / f1a152c |
| Console output |
https://builds.apache.org/job/PreCommit-MAPREDUCE-Build/5566/console |
This message was automatically generated.
> mappers get rescheduled on node transition even after all reducers are
> completed
> --------------------------------------------------------------------------------
>
> Key: MAPREDUCE-5817
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-5817
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Components: applicationmaster
> Affects Versions: 2.3.0
> Reporter: Sangjin Lee
> Assignee: Sangjin Lee
> Attachments: mapreduce-5817.patch
>
>
> We're seeing a behavior where a job runs long after all reducers were already
> finished. We found that the job was rescheduling and running a number of
> mappers beyond the point of reducer completion. In one situation, the job ran
> for some 9 more hours after all reducers completed!
> This happens because whenever a node transition (to an unusable state) comes
> into the app master, it just reschedules all mappers that already ran on the
> node in all cases.
> Therefore, if any node transition has a potential to extend the job period.
> Once this window opens, another node transition can prolong it, and this can
> happen indefinitely in theory.
> If there is some instability in the pool (unhealthy, etc.) for a duration,
> then any big job is severely vulnerable to this problem.
> If all reducers have been completed, JobImpl.actOnUnusableNode() should not
> reschedule mapper tasks. If all reducers are completed, the mapper outputs
> are no longer needed, and there is no need to reschedule mapper tasks as they
> would not be consumed anyway.
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