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From "Arun C Murthy (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-3333) job failing because of reassigning same tasktracker to failing tasks
Date Fri, 02 May 2008 15:36:55 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-3333?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12593797#action_12593797
] 

Arun C Murthy commented on HADOOP-3333:
---------------------------------------

bq. Number of blacklisted TaskTrackers is low (less than 1%), because we have a high threshold
(100 failures) for TaskTrackers to be declared blacklisted.

Christian, the notion of blacklisting is useful to ensure that tasks aren't scheduled on the
marginal tasktrackers. That said, the scheduling code in the JobTracker tries to not allocate
on nodes on which it hasn't previously been executed, unless it has failed on all machines.
What is your configuration for mapred.reduce.max.attempts?

bq. I can point you to a running job offline exhibiting the problem.
Yes, that will help. Thanks!

> job failing because of reassigning same tasktracker to failing tasks
> --------------------------------------------------------------------
>
>                 Key: HADOOP-3333
>                 URL: https://issues.apache.org/jira/browse/HADOOP-3333
>             Project: Hadoop Core
>          Issue Type: Bug
>          Components: mapred
>    Affects Versions: 0.16.3
>            Reporter: Christian Kunz
>            Priority: Blocker
>
> We have a long running a job in a 2nd atttempt. Previous job was failing and current
jobs risks to fail as well, because  reduce tasks failing on marginal TaskTrackers are assigned
repeatedly to the same TaskTrackers (probably because it is the only available slot), eventually
running out of attempts.
> Reduce tasks should be assigned to the same TaskTrackers at most twice, or TaskTrackers
need to get some better smarts to find  failing hardware.
> BTW, mapred.reduce.max.attempts=12, which is high, but does not help in this case.

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