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From "Arun C Murthy (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-1158) JobTracker should collect statistics of failed map output fetches, and take decisions to reexecute map tasks and/or restart the (possibly faulty) Jetty server on the TaskTracker
Date Thu, 07 Jun 2007 04:06:26 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-1158?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12502212
] 

Arun C Murthy commented on HADOOP-1158:
---------------------------------------

Oh, it might be worth considering a separate MapTaskStatus and ReduceTaskStatus classes since
there are varied pieces of un-related information for Map and Reduce tasks (i.e. shuffle/sort-merge
related info, fetch failures etc.) ... we could stick it up in the appropriate 'Task' class
too (which the child-vm could then compute and send to the TaskTracker) - perhaps as a separate
issue?

> JobTracker should collect statistics of failed map output fetches, and take decisions
to reexecute map tasks and/or restart the (possibly faulty) Jetty server on the TaskTracker
> ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: HADOOP-1158
>                 URL: https://issues.apache.org/jira/browse/HADOOP-1158
>             Project: Hadoop
>          Issue Type: Improvement
>          Components: mapred
>    Affects Versions: 0.12.2
>            Reporter: Devaraj Das
>            Assignee: Arun C Murthy
>
> The JobTracker should keep a track (with feedback from Reducers) of how many times a
fetch for a particular map output failed. If this exceeds a certain threshold, then that map
should be declared as lost, and should be reexecuted elsewhere. Based on the number of such
complaints from Reducers, the JobTracker can blacklist the TaskTracker. This will make the
framework reliable - it will take care of (faulty) TaskTrackers that sometimes always fail
to serve up map outputs (for which exceptions are not properly raised/handled, for e.g., if
the exception/problem happens in the Jetty server).

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