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Date: Thu, 23 Feb 2006 00:01:38 +0100 (CET)
From: "Doug Cutting (JIRA)" <jira@apache.org>
To: hadoop-dev@lucene.apache.org
Subject: [jira] Commented: (HADOOP-41) JAVA_OPTS for the TaskRunner Child
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    [ http://issues.apache.org/jira/browse/HADOOP-41?page=comments#action_12367435 ] 

Doug Cutting commented on HADOOP-41:
------------------------------------

I like this, except that it is not back-compatible.  We should continue to support mapred.child.heap.size, so that folks who upgrade are not broken.

> JAVA_OPTS for the TaskRunner Child
> ----------------------------------
>
>          Key: HADOOP-41
>          URL: http://issues.apache.org/jira/browse/HADOOP-41
>      Project: Hadoop
>         Type: Improvement
>   Components: conf
>     Reporter: stack@archive.org
>     Priority: Minor
>  Attachments: TaskRunner_child_javaopts.patch
>
> Currently, its possible to set the java heap size the TaskRunner child runs in, but thats all thats configurable about the child process.  Hereabouts, we've found it useful being able to specify other options for the child JVM, especially when debugging and monitoring long-lived processes.  
> Examples of why its useful being able to set options are the child include:
> + Being able to set '-server' option or '-c64'.
> + Passing logging.properties to configure child logging.
> + Enable and capture to file verbose GC logging or start the SUN JVM JMX agent for the child process.  Allows connecting with jconsole to watch long-lived children, their heap and thread usage, and when seemingly hung, take thread dumps.

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