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From "Owen O'Malley (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-3280) virtual address space limits break streaming apps
Date Mon, 21 Apr 2008 20:17:22 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-3280?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12591032#action_12591032
] 

Owen O'Malley commented on HADOOP-3280:
---------------------------------------

Very good point, Allen. I think we should just revert HADOOP-2765 and just assume that the
admin configuring the cluster sets it in $conf/hadoop-env.sh on the task trackers. The only
downside is that the task trackers would be under the same ram limitation as the sub-processes.
But that seems ok.

> virtual address space limits break streaming apps
> -------------------------------------------------
>
>                 Key: HADOOP-3280
>                 URL: https://issues.apache.org/jira/browse/HADOOP-3280
>             Project: Hadoop Core
>          Issue Type: Bug
>          Components: contrib/streaming
>            Reporter: Rick Cox
>            Priority: Blocker
>             Fix For: 0.17.0
>
>         Attachments: HADOOP-3280_0_20080418.patch
>
>
> HADOOP-2765 added a mandatory, hard virtual address space limit to streaming apps based
on the Java process's -Xmx setting.
> This makes it impossible to run a 64-bit streaming app that needs large address spaces
under a 32-bit JVM, even if one is otherwise willing to dramatically increase the -Xmx setting
without cause. Also, unlike Java's -Xmx limit, the virtual address space limit for an arbitrary
UNIX process does not necessarily correspond to RAM usage, so it's likely to be a relatively
difficult to configure limit.
> 2765 was originally opened to allow an optional wrapper script around streaming tasks,
one use case for which was setting a ulimit. That approach seems much less intrusive and more
flexible than the final implementation. The ulimit can also be trivially set by the streaming
task itself without any support from Hadoop.
> Marking this as an 0.17 blocker because it will break deployed apps and there is no workaround
available.

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