[jira] [Commented] (MAPREDUCE-4820) MRApps distributed-cache duplicate checks are incorrect

["Robert Joseph Evans (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/MAPREDUCE-4820?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13609277#comment-13609277 ] 

Robert Joseph Evans commented on MAPREDUCE-4820:
------------------------------------------------

Alejandro,

MAPREDUCE-4549 is the thing that undid MAPREDUCE-4503.  MAPREDUCE-4503 made it an exception to have distributed cache collisions.  MAPREDUCE-4549, which is fixed in 2.0.4-alpha, turned that error into a warning.  I suspect you just need to go to 2.0.4-alpha and your issue is "fixed". 

We still need to decided if we want to put the warning into trunk as well, or if there is a viable long term solution where oozie and others can be sure to not have duplicate entries.
                
> MRApps distributed-cache duplicate checks are incorrect
> -------------------------------------------------------
>
>                 Key: MAPREDUCE-4820
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-4820
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>          Components: mr-am
>    Affects Versions: 2.0.2-alpha
>            Reporter: Alejandro Abdelnur
>            Priority: Blocker
>             Fix For: 2.0.4-alpha
>
>         Attachments: launcher-job.conf.xml, launcher-job.logs.txt, mr-job.conf.xml, mr-job.logs.txt
>
>
> This seems a combination of issues that are being exposed in 2.0.2-alpha by MAPREDUCE-4549.
> MAPREDUCE-4549 introduces a check to to ensure there are not duplicate JARs in the distributed-cache (using the JAR name as identity).
> In Hadoop 2 (different from Hadoop 1), all JARs in the distributed-cache are symlink-ed to the current directory of the task.
> MRApps, when setting up the DistributedCache (MRApps#setupDistributedCache->parseDistributedCacheArtifacts) assumes that the local resources (this includes files in the CURRENT_DIR/, CURRENT_DIR/classes/ and files in CURRENT_DIR/lib/) are part of the distributed-cache already.
> For systems, like Oozie, which use a launcher job to submit the real job this poses a problem because MRApps is run from the launcher job to submit the real job. The configuration of the real job has the correct distributed-cache entries (no duplicates), but because the current dir has the same files, the submission fails.
> It seems that MRApps should not be checking dups in the distributed-cached against JARs in the CURRENT_DIR/ or CURRENT_DIR/lib/. The dup check should be done among distributed-cached entries only.
> It seems YARNRunner is symlink-ing all files in the distributed cached in the current directory. In Hadoop 1 this was done only for files added to the distributed-cache using a fragment (ie "#FOO") to trigger a symlink creation. 
> Marking as a blocker because without a fix for this, Oozie cannot submit jobs to Hadoop 2 (i've debugged Oozie in a live cluster being used by BigTop -thanks Roman- to test their release work, and I've verified that Oozie 3.3 does not create duplicated entries in the distributed-cache)

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