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https://issues.apache.org/jira/browse/MAPREDUCE-3274?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13136362#comment-13136362
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Robert Joseph Evans commented on MAPREDUCE-3274:
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>From what I can see in the code. The simplest thing to do appears to be
>inside AssignedRequests.add check preemptionWaitingReduces, when assigning the
>container, and then if it is there, re-issue the TA_KILL event.
I am not sure that this is the correct thing to do, as a TA_KILL has already
been issued. I will try to trace down the events associated with these.
> Race condition in MR App Master Preemtion can cause a dead lock
> ---------------------------------------------------------------
>
> Key: MAPREDUCE-3274
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-3274
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Components: mrv2, scheduler
> Affects Versions: 0.23.0, 0.24.0
> Reporter: Robert Joseph Evans
> Assignee: Robert Joseph Evans
> Priority: Critical
> Fix For: 0.23.0, 0.24.0
>
>
> There appears to be a race condition in the MR App Master in relation to
> preempting reducers to let a mapper run. In the particular case that I have
> been debugging a reducer was selected for preemption that did not have a
> container assigned to it yet. When the container became available that reduce
> started running and the previous TA_KILL event appears to have been ignored.
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