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From "Ray Chiang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MAPREDUCE-6622) Add capability to set JHS job cache to a task-based limit
Date Mon, 01 Feb 2016 19:26:39 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-6622?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15126860#comment-15126860
] 

Ray Chiang commented on MAPREDUCE-6622:
---------------------------------------

While I do have some doubts about general Guava library compatibility, I don't have a lot
with their Cache library.  While I was trying to figure out how to implement this, I wrote
up some separate code using the latest (v19) and the same API calls worked fine in the upstream
tree (v11).

> Add capability to set JHS job cache to a task-based limit
> ---------------------------------------------------------
>
>                 Key: MAPREDUCE-6622
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-6622
>             Project: Hadoop Map/Reduce
>          Issue Type: Improvement
>          Components: jobhistoryserver
>    Affects Versions: 2.7.2
>            Reporter: Ray Chiang
>            Assignee: Ray Chiang
>              Labels: supportability
>         Attachments: MAPREDUCE-6622.001.patch, MAPREDUCE-6622.002.patch
>
>
> When setting the property mapreduce.jobhistory.loadedjobs.cache.size the jobs can be
of varying size.  This is generally not a problem when the jobs sizes are uniform or small,
but when the job sizes can be very large (say greater than 250k tasks), then the JHS heap
size can grow tremendously.
> In cases, where multiple jobs are very large, then the JHS can lock up and spend all
its time in GC.  However, since the cache is holding on to all the jobs, not much heap space
can be freed up.
> By setting a property that sets a cap on the number of tasks allowed in the cache and
since the total number of tasks loaded is directly proportional to the amount of heap used,
this should help prevent the JHS from locking up.



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