[
https://issues.apache.org/jira/browse/HADOOP-1158?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12511034
]
Devaraj Das commented on HADOOP-1158:
-------------------------------------
One comment - for cases where a reduce fails to fetch a map output for a number
of times, it informs the jobtracker, and the jobtracker reexecutes the map. The
reduce task also increments a counter associated with the number of failed
fetches (which in the patch is used to kill itself when it exceeds a certain
number). Now if the reduce can fetch the map output correctly from the new map
location, it should decrement that counter.
> 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
> Attachments: HADOOP-1158_20070702_1.patch
>
>
> 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).
--
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.
