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From "Aaron Kimball (JIRA)" <j...@apache.org>
Subject [jira] Commented: (MAPREDUCE-825) JobClient completion poll interval of 5s causes slow tests in local mode
Date Wed, 05 Aug 2009 18:07:14 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-825?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12739650#action_12739650
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Aaron Kimball commented on MAPREDUCE-825:
-----------------------------------------

Agreed about the other timeout. I'll include that as well.

I can change the suggested test, but as you say, it'll have to be a manual verification and
that'll itself be subjective. Thread.sleep(n) guarantees that a thread will sleep for at least
'n' milliseconds, or receive an InterruptedException. But the OS is always free to reschedule
your thread later, and there are a lot of other variable-time components in these tests. So
writing JUnit tests that compare relative runtimes might nondeterministically fail.

I'll report back results.

> JobClient completion poll interval of 5s causes slow tests in local mode
> ------------------------------------------------------------------------
>
>                 Key: MAPREDUCE-825
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-825
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>            Reporter: Aaron Kimball
>            Assignee: Aaron Kimball
>            Priority: Minor
>         Attachments: completion-poll-interval.patch
>
>
> The JobClient.NetworkedJob.waitForCompletion() method polls for job completion every
5 seconds. When running a set of short tests in pseudo-distributed mode, this is unnecessarily
slow and causes lots of wasted time. When bandwidth is not scarce, setting the poll interval
to 100 ms results in a 4x speedup in some tests.  This interval should be parametrized to
allow users to control the interval for testing purposes.

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