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From "Scott Chen (JIRA)" <j...@apache.org>
Subject [jira] Commented: (MAPREDUCE-1829) JobInProgress.findSpeculativeTask should use min() to find the candidate instead of sort()
Date Tue, 08 Jun 2010 17:49:12 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-1829?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12876742#action_12876742
] 

Scott Chen commented on MAPREDUCE-1829:
---------------------------------------

The tests failed because of class not found exception.
For example, java.lang.NoClassDefFoundError: org/apache/hadoop/security/RefreshUserToGroupMappingsProtocol

I do not know why this happened.
I have manually run the test, TestSpeculativeExecution which covers this code path and it
succeed.
{code}
Testsuite: org.apache.hadoop.mapred.TestSpeculativeExecution
Tests run: 5, Failures: 0, Errors: 0, Time elapsed: 39.893 sec
{code}

There is no unit test included because the code path is been tested by the existing TestSpeculativeExecution.
I am submitting this to Hudson again.

> JobInProgress.findSpeculativeTask should use min() to find the candidate instead of sort()
> ------------------------------------------------------------------------------------------
>
>                 Key: MAPREDUCE-1829
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-1829
>             Project: Hadoop Map/Reduce
>          Issue Type: Improvement
>          Components: jobtracker
>    Affects Versions: 0.22.0
>            Reporter: Scott Chen
>            Assignee: Scott Chen
>             Fix For: 0.22.0
>
>         Attachments: MAPREDUCE-1829.txt
>
>
> findSpeculativeTask needs only one candidate to speculate so it does not need to sort
the whole list. It may looks OK but someone can still submit big jobs with small slow task
thresholds. In this case, this sorting becomes expensive.

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