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https://issues.apache.org/jira/browse/MAPREDUCE-7033?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Jason Lowe reassigned MAPREDUCE-7033:
-------------------------------------

            Assignee: Jason Lowe
            Priority: Critical  (was: Major)
    Target Version/s: 3.1.0, 3.0.1

Raising the priority of this since I recently discovered this long-lingering 
bug can actually prevent proper shuffling on secure clusters in Hadoop 3.x.

HADOOP-11347 fixed a bug in the local filesystem so it started honoring the 
configured fs.permissions.umask-mode for local files.  That fix now exposes the 
lack of explicit permissions in the MapReduce framework for any case where the 
configured umask is at least 0044.


> Map outputs implicitly rely on permissive umask for shuffle
> -----------------------------------------------------------
>
>                 Key: MAPREDUCE-7033
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-7033
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>          Components: mrv2
>            Reporter: Jason Lowe
>            Assignee: Jason Lowe
>            Priority: Critical
>
> Map tasks do not explicitly set the permissions of their output files for 
> shuffle.  In a secure cluster the shuffle service is running as a different 
> user than the map task, so the output files require group readability in 
> order to serve up the data during the shuffle phase.  If the user's UNIX 
> umask is too restrictive (e.g.: 077) then the map task's file.out and 
> file.out.index permissions can be too restrictive to allow the shuffle 
> handler to access them.



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