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From "Jothi Padmanabhan (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-3333) job failing because of reassigning same tasktracker to failing tasks
Date Fri, 13 Jun 2008 11:22:45 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-3333?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12604804#action_12604804
] 

Jothi Padmanabhan commented on HADOOP-3333:
-------------------------------------------

It appears that the only way to handle the case of multiple TTs per node is to trickle down
the list of uniques hosts (that run TT) down from the JobTracker (hostsReader.getHosts().size()).
This information needs to trickle down through several layers before it can be used in findTaskFromList.
We need to evaluate if we want to make this change to handle this special case or just go
ahead with the existing patch and document this case as a limitation.

> 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
>            Assignee: Jothi Padmanabhan
>            Priority: Blocker
>             Fix For: 0.18.0
>
>         Attachments: HADOOP-3333_0_20080503.patch, HADOOP-3333_1_20080505.patch, HADOOP-3333_2_20080506.patch
>
>
> 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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