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From "Amareshwari Sriramadasu (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-6014) Improvements to Global Black-listing of TaskTrackers
Date Fri, 19 Jun 2009 09:03:07 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-6014?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12721701#action_12721701

Amareshwari Sriramadasu commented on HADOOP-6014:

bq. But it is very hard to draw the inference the other way when you may have a run of "bad"
jobs that are all expected to fail.
Current blacklisting strategy looks at trackers blacklisted by Successful jobs. Also, a TT
gets blacklisted onlyif #blacklists for the tracker is 50% above the average #blacklists,
over the active and potentially faulty trackers

> Improvements to Global Black-listing of TaskTrackers
> ----------------------------------------------------
>                 Key: HADOOP-6014
>                 URL: https://issues.apache.org/jira/browse/HADOOP-6014
>             Project: Hadoop Core
>          Issue Type: Improvement
>          Components: mapred
>    Affects Versions: 0.20.0
>            Reporter: Arun C Murthy
>             Fix For: 0.21.0
> HADOOP-4305 added a global black-list of tasktrackers.
> We saw a scenario on one of our clusters where a few jobs caused a lot of tasktrackers
to immediately be blacklisted. This was caused by a specific set of jobs which (same user)
whose tasks were shot down the by the TaskTracker for being over the vmem limit of 2G. Each
of these jobs had over 600 failures of the same kind. This resulted in each of the users black-listing
some tasktrackers, which in itself is wrong since the failures had nothing to do with the
node on which the failure occurred (i.e. high memory usage) and shouldn't have had to penalized
the tasktracker. We clearly need to start treating system and user failures separately for
black-listing etc. A DiskError is fatal and should probably we blacklisted immediately while
a task which was 'failed' for using more memory shouldn't count against the tasktracker at
> The other problem is that we never configured mapred.max.tracker.blacklists and continue
to use the default value of 4. Further more this config should really be a percent of the
cluster-size and not a whole number. 

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