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https://issues.apache.org/jira/browse/MAPREDUCE-6870?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16123624#comment-16123624
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Haibo Chen commented on MAPREDUCE-6870:
---------------------------------------

Thanks [~xkrogen] for pointing out the incompatibility! I agree. Maybe we even 
need to flip the default to false in order to avoid the incompatible, since the 
case this is trying to fix is an edge case to begin with.

> Add configuration for MR job to finish when all reducers are complete (even 
> with unfinished mappers)
> ----------------------------------------------------------------------------------------------------
>
>                 Key: MAPREDUCE-6870
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-6870
>             Project: Hadoop Map/Reduce
>          Issue Type: Improvement
>    Affects Versions: 2.6.1
>            Reporter: Zhe Zhang
>            Assignee: Peter Bacsko
>             Fix For: 3.0.0-beta1
>
>         Attachments: MAPREDUCE-6870-001.patch, MAPREDUCE-6870-002.patch, 
> MAPREDUCE-6870-003.patch, MAPREDUCE-6870-004.patch, MAPREDUCE-6870-005.patch, 
> MAPREDUCE-6870-006.patch, MAPREDUCE-6870-007.patch
>
>
> Even with MAPREDUCE-5817, there could still be cases where mappers get 
> scheduled before all reducers are complete, but those mappers run for long 
> time, even after all reducers are complete. This could hurt the performance 
> of large MR jobs.
> In some cases, mappers don't have any materialize-able outcome other than 
> providing intermediate data to reducers. In that case, the job owner should 
> have the config option to finish the job once all reducers are complete.



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