[jira] Updated: (HADOOP-4018) limit memory usage in jobtracker

["Arun C Murthy (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HADOOP-4018?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Arun C Murthy updated HADOOP-4018:
----------------------------------

    Status: Open  (was: Patch Available)

Cancelling patch while Amar's comments are being accomodated...

Minor nit: the variable maxSplits in JobInProgress should probably be renamed to 'maxTasks' - it's misleading.
I'm not super excited about using 0 as the default value for mapred.max.tasks.per.job - this has come up before and I guess we need to come up with a way of specifying 'UNLIMITED' in our configuration files.

> limit memory usage in jobtracker
> --------------------------------
>
>                 Key: HADOOP-4018
>                 URL: https://issues.apache.org/jira/browse/HADOOP-4018
>             Project: Hadoop Core
>          Issue Type: Bug
>          Components: mapred
>            Reporter: dhruba borthakur
>            Assignee: dhruba borthakur
>         Attachments: maxSplits.patch, maxSplits2.patch, maxSplits3.patch, maxSplits4.patch, maxSplits5.patch, maxSplits6.patch, maxSplits7.patch, maxSplits8.patch
>
>
> We have seen instances when a user submitted a job with many thousands of mappers. The JobTracker was running with 3GB heap, but it was still not enough to prevent memory trashing from Garbage collection; effectively the Job Tracker was not able to serve jobs and had to be restarted.
> One simple proposal would be to limit the maximum number of tasks per job. This can be a configurable parameter. Is there other things that eat huge globs of memory in job Tracker?

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