[jira] Commented: (HADOOP-6014) Improvements to Global Black-listing of TaskTrackers

["Jim Huang (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HADOOP-6014?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12718696#action_12718696 ] 

Jim Huang commented on HADOOP-6014:
-----------------------------------

In HADOOP-5478, we are asking for the ability to blacklist a tasktrackers via a node health check script.  This should help to differentiate detectable system failures against user/application failures.  Please take HADOOP-5478 as a consideration for this bug.

> 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 all!
> 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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