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From "Rick Cox (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-3280) virtual address space limits break streaming apps
Date Fri, 18 Apr 2008 22:34:21 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-3280?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12590633#action_12590633
] 

Rick Cox commented on HADOOP-3280:
----------------------------------

The prologue idea seems to support the variety of uses easily. I like it. To make sure I understand:

The prologue setting would first be tokenized using the same parser as is used for the regular
command, and we'd then concatenate the list of prologue tokens with the list of regular command
tokens.

Use cases would include:

Setting a ulimit: {{prologue="bash -c ulimit -v NNN; exec"}}

Adding a wrapper: {{prologue="wrapper.sh"}}
where wrapper.sh could be:
{code}
#!/bin/bash

...set environment variables, ulimits, etc...

exec "$@"
{code}

Or just directly executing the command: {{prologue=""}}.

Since this will only apply to streaming (and possibly pipes), should the setting name be {{stream.task.prologue}}?



> 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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