[jira] Commented: (HADOOP-137) Different TaskTrackers may get the same task tracker id, thus cause many problems.

["Runping Qi (JIRA)" <ji...@apache.org>]

    [ http://issues.apache.org/jira/browse/HADOOP-137?page=comments#action_12374587 ] 

Runping Qi commented on HADOOP-137:
-----------------------------------


A simple fix for the issue is to add hostname as part of task track names. 
I believe Owen has actually done this in trying to fix another issue, but the patch
is not committed yet.



> Different TaskTrackers may get the same task tracker id, thus cause many problems.
> ----------------------------------------------------------------------------------
>
>          Key: HADOOP-137
>          URL: http://issues.apache.org/jira/browse/HADOOP-137
>      Project: Hadoop
>         Type: Bug

>   Components: mapred
>     Reporter: Runping Qi
>     Priority: Critical

>
> In the TaskTracker#Initialize method, the following line assigns task tracker name (id):
> this.taskTrackerName = "tracker_" + (Math.abs(r.nextInt()) % 100000);
> For a fair size cluster, it is possible that different task trackers to get the same id, causing name conflict.
> I encountered this problem with a cluster of 274 nodes. Once such conflict happens, a lot of strange things may happen.
> For example, a reducer task tried to copy from a machine (task tracker) a map output file that was actually produced 
> on another machine.

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