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https://issues.apache.org/jira/browse/MAPREDUCE-114?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12844220#action_12844220
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Koji Noguchi commented on MAPREDUCE-114:
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Is this related to MAPREDUCE-1060 ?

> All reducer tasks are finished, while some mapper tasks are still running
> -------------------------------------------------------------------------
>
>                 Key: MAPREDUCE-114
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-114
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>            Reporter: Qi Liu
>         Attachments: hadoop-bug-overview.png, hadoop-bug-useless-task.png
>
>
> In a high load environment (i.e. multiple jobs are queued up to be executed), 
> when all reducer tasks of a job are finished, some mapper tasks of the same 
> job may still running (possibly re-executed due to lost task tracker, etc).
> This should not happen when a job has at least one reducer task. When all 
> reducer tasks are in SUCCEEDED state, the Hadoop JobTracker should kill all 
> running mapper tasks, since execution would be meaningless. The job should 
> also switch to SUCCEEDED state when all reducer tasks of that job succeeded 
> successfully.

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