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https://issues.apache.org/jira/browse/MAPREDUCE-1247?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Zheng Shao reassigned MAPREDUCE-1247:
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    Assignee: ZhuGuanyin

> Send out-of-band heartbeat to avoid fake lost tasktracker
> ---------------------------------------------------------
>
>                 Key: MAPREDUCE-1247
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-1247
>             Project: Hadoop Map/Reduce
>          Issue Type: New Feature
>            Reporter: ZhuGuanyin
>            Assignee: ZhuGuanyin
>
> Currently the TaskTracker report task status to jobtracker through heartbeat, 
> sometimes if the tasktracker  lock the tasktracker to do some cleanup  job, 
> like remove task temp data on disk, the heartbeat thread would hang for a 
> long time while waiting for the lock, so the jobtracker just thought it had 
> lost and would reschedule all its finished maps or un finished reduce on 
> other tasktrackers, we call it "fake lost tasktracker", some times it doesn't 
> acceptable especially when we run some large jobs.  So We introduce a 
> out-of-band heartbeat mechanism to send an out-of-band heartbeat in that case.

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