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https://issues.apache.org/jira/browse/MAPREDUCE-1247?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12783899#action_12783899
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Arun C Murthy commented on MAPREDUCE-1247:
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I agree with Todd, we should *never* do any i/o operation holding locks...
we've added the taskcleanup thread long ago for precisely the same reason. It
is quite possible that we've since violated that - we should fix the primary
cause rather than hide it with out-of-band heartbeats.
> 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
>
> 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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