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From "Jason Lowe (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MAPREDUCE-6889) Provide an API Job#close to shutdown MR client services.
Date Tue, 16 May 2017 15:57:04 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-6889?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16012632#comment-16012632
] 

Jason Lowe commented on MAPREDUCE-6889:
---------------------------------------

I don't know the full history behind the newInstance call.  Some software archaeology shows
the newInstance change was added during the review rework process for YARN-4696, but even
before that the code was explicitly setting the conf key to disable caching for the filesystem.
 The disabling of the filesystem cache was done partway through the review on YARN-4234 but
I could not find a discussion that explained why that addition to the patch was necessary.
 Pinging [~xgong] and [~gtCarrera9] to see if they know the logic behind avoiding the fs cache
in FileSystemTimelineWriter.

> Provide an API Job#close to shutdown MR client services.
> --------------------------------------------------------
>
>                 Key: MAPREDUCE-6889
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-6889
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>            Reporter: Rohith Sharma K S
>            Assignee: Rohith Sharma K S
>         Attachments: MAPREDUCE-6889.0001.patch
>
>
> ATS1.5 uses FileSystemTimelineWriter which creates FS object on every writer initialization.
If writer is not closed, then there is possibility of OOM see YARN-5438 fixes closing FS object.

> TimelineClient is used by YarnClient. So all the user who uses YarnClient with ATS1.5
need to stop service properly. Otherwise there is big chance of FS object leak. 
> Of course MR uses YARN client submit job. If MR do not stop YarnClient then there is
FS object leak. 
> JobClient provides a API to stop all these service using *JobClient#close*. But many
MR clients uses *Job* object to submit a job. But  do not stop started services by default.

> So, provide a API *Job#close* to shutdown MR client services. This API can be utilized
by caller explicitly to stop service which avoids FS leak. 



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