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From "Allen Wittenauer (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MAPREDUCE-2489) Jobsplits with random hostnames can make the queue unusable
Date Thu, 12 May 2011 23:00:47 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-2489?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13032738#comment-13032738
] 

Allen Wittenauer commented on MAPREDUCE-2489:
---------------------------------------------

I'm assuming no nscd or dns cache was running on the JT?

> Jobsplits with random hostnames can make the queue unusable
> -----------------------------------------------------------
>
>                 Key: MAPREDUCE-2489
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-2489
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>          Components: jobtracker
>            Reporter: Jeffrey Naisbitt
>            Assignee: Jeffrey Naisbitt
>
> We saw an issue where a custom InputSplit was returning invalid hostnames for the splits
that were then causing the JobTracker to attempt to excessively resolve host names.  This
caused a major slowdown for the JobTracker.  We should prevent invalid InputSplit hostnames
from affecting everyone else.
> I propose we implement some verification for the hostnames to try to ensure that we only
do DNS lookups on valid hostnames (and fail otherwise).  We could also fail the job after
a certain number of failures in the resolve.

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