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From "Torsten Curdt (JIRA)" <j...@apache.org>
Subject [jira] Commented: (MAPREDUCE-1853) MultipleOutputs does not cache TaskAttemptContext
Date Sun, 13 Jun 2010 10:11:14 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-1853?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12878375#action_12878375
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Torsten Curdt commented on MAPREDUCE-1853:
------------------------------------------

Patch updated. Should apply also with -p0 now.

> MultipleOutputs does not cache TaskAttemptContext
> -------------------------------------------------
>
>                 Key: MAPREDUCE-1853
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-1853
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>    Affects Versions: 0.21.0
>         Environment: OSX 10.6
> java6
>            Reporter: Torsten Curdt
>            Priority: Critical
>         Attachments: cache-task-attempts.diff
>
>
> In MultipleOutputs there is
> [code]
>  private TaskAttemptContext getContext(String nameOutput) throws IOException {
>     // The following trick leverages the instantiation of a record writer via
>     // the job thus supporting arbitrary output formats.
>     Job job = new Job(context.getConfiguration());
>     job.setOutputFormatClass(getNamedOutputFormatClass(context, nameOutput));
>     job.setOutputKeyClass(getNamedOutputKeyClass(context, nameOutput));
>     job.setOutputValueClass(getNamedOutputValueClass(context, nameOutput));
>     TaskAttemptContext taskContext = 
>       new TaskAttemptContextImpl(job.getConfiguration(), 
>                                  context.getTaskAttemptID());
>     return taskContext;
>   }
> [code]
> so for every reduce call it creates a new Job instance ...which creates a new LocalJobRunner.
> That does not sound like a good idea.
> You end up with a flood of "jvm.JvmMetrics: Cannot initialize JVM Metrics with processName=JobTracker,
sessionId= - already initialized"
> This should probably also be added to 0.22.

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