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https://issues.apache.org/jira/browse/MAPREDUCE-6689?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15272988#comment-15272988
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Wangda Tan commented on MAPREDUCE-6689:
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Uploaded patch for this (on top of MAPREDUCE-6514)
> MapReduce job can infinitely increase number of reducer resource requests
> -------------------------------------------------------------------------
>
> Key: MAPREDUCE-6689
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-6689
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Reporter: Wangda Tan
> Assignee: Wangda Tan
> Priority: Blocker
> Attachments: MAPREDUCE-6689.1.patch
>
>
> We have seen this issue from one of our clusters: when running terasort
> map-reduce job, some mappers failed after reducer started, and then MR AM
> tries to preempt reducers to schedule these failed mappers.
> After that, MR AM enters an infinite loop, for every
> RMContainerAllocator#heartbeat run, it:
> - In {{preemptReducesIfNeeded}}, it cancels all scheduled reducer requests.
> (total scheduled reducers = 1024)
> - Then, in {{scheduleReduces}}, it ramps up all reducers (total = 1024).
> As a result, we can see total #requested-containers increased 1024 for every
> MRAM-RM heartbeat (1 sec per heartbeat). The AM is hanging for 18+ hours, so
> we get 18 * 3600 * 1024 ~ 66M+ requested containers in RM side.
> And this bug also triggered YARN-4844, which makes RM stop scheduling
> anything.
> Thanks to [~sidharta-s] for helping with analysis.
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