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https://issues.apache.org/jira/browse/MAPREDUCE-6275?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14364000#comment-14364000
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Siqi Li commented on MAPREDUCE-6275:
------------------------------------

In FileOutputCommiter v2, multiple reducers may call commitTask at the same 
time. If the outputs of reducers have directory structure with the same name, 
it may encounter problems with v2.

For example, if reducerA has output Dir1/File1, reducerB has output Dir1/File2. 
Since final output directory doesn't have Dir1, both reducers may call rename 
at the same time. This would end up with weird output directory structure 
like(Dir1/Dir1/File1, or Dir1/Dir/File2).

Therefore, we should remove FileSystem.rename from 
FileOutputCommitter#mergePaths method.

> Potential race condition of mutiple file system rename in FileOutputCommiter 
> v2
> -------------------------------------------------------------------------------
>
>                 Key: MAPREDUCE-6275
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-6275
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>            Reporter: Siqi Li
>




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