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From "Vladimir Klimontovich (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MAPREDUCE-4715) Heap memory growing when JVM reuse option enabled
Date Tue, 09 Oct 2012 14:43:03 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-4715?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13472432#comment-13472432

Vladimir Klimontovich commented on MAPREDUCE-4715:

FileSystem class keeps a static cache of all FileSystem objects. See FileSystem#CACHE static
field. The cache key is a pair of file system URI (string) and Configuration object. To fix
that I'd suggest to run FileSystem.closeAll() (which clears the cache) somewhere in the cleanup
section of TaskRunner.java
> Heap memory growing when JVM reuse option enabled
> -------------------------------------------------
>                 Key: MAPREDUCE-4715
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-4715
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>          Components: job submission
>    Affects Versions: 0.20.2
>         Environment: Linux, cdh3u5
>            Reporter: Boris Ryakhovskiy
>            Priority: Minor
>         Attachments: VisualVM_screenshot.png
> When mapred.job.reuse.jvm.num.tasks option is set to 100 or more tasks, JVM fails with
"java.lang.OutOfMemoryError: Java heap space" error message. Jobs itself are small and job
heap size is set to -Xmx200m .
> It looks like the reason of the issue is a FileSystem$Cache object which collects JobConf
objects from all jobs which were executed in current JVM. GC root for the FileSystem$Cache
is ApplicationShutdownHooks class (cannot attach screenshot from visualvm)
> In my case each of JobConf objects allocates ~500K (50M total in case of 100 jobs).

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