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https://issues.apache.org/jira/browse/MAPREDUCE-3274?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13137122#comment-13137122
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Robert Joseph Evans commented on MAPREDUCE-3274:
------------------------------------------------

You are correct, I got confused by the JVM ID not lining up with the 
attempt/task ID.  The r_000008 is confusing.  I will keep digging.  The 
deadlock has been fairly reproducible, but I end up with about 20GB of logs to 
go through afterwards so it has taken me a while to get through them all.
                
> 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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