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From "Todd Lipcon (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MAPREDUCE-2740) MultipleOutputs in new API creates needless TaskAttemptContexts
Date Sat, 30 Jul 2011 00:35:09 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-2740?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13073085#comment-13073085

Todd Lipcon commented on MAPREDUCE-2740:

Ran local test-patch:

     [exec] -1 overall.  
     [exec]     +1 @author.  The patch does not contain any @author tags.
     [exec]     -1 tests included.  The patch doesn't appear to include any new or modified
     [exec]                         Please justify why no new tests are needed for this patch.
     [exec]                         Also please list what manual steps were performed to verify
this patch.
     [exec]     +1 javadoc.  The javadoc tool did not generate any warning messages.
     [exec]     +1 javac.  The applied patch does not increase the total number of javac compiler
     [exec]     -1 findbugs.  The patch appears to introduce -7 new Findbugs (version 1.3.8)
     [exec]     +1 release audit.  The applied patch does not increase the total number of
release audit warnings.
     [exec]     +1 system test framework.  The patch passed system test framework compile.

- No tests are included since it's an optimization, and covered by original tests.
- the findbugs warning is clearly bogus -- negative 7?

> MultipleOutputs in new API creates needless TaskAttemptContexts
> ---------------------------------------------------------------
>                 Key: MAPREDUCE-2740
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-2740
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>    Affects Versions: 0.23.0
>            Reporter: Todd Lipcon
>            Assignee: Todd Lipcon
>             Fix For: 0.23.0
>         Attachments: mr-2740.txt
> MultipleOutputs.write creates a new TaskAttemptContext, which we've seen to take a significant
amount of CPU. The TaskAttemptContext constructor creates a JobConf, gets current UGI, etc.
I don't see any reason it needs to do this, instead of just creating a single TaskAttemptContext
when the InputFormat is created (or lazily but cached as a member)

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