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https://issues.apache.org/jira/browse/MAPREDUCE-1247?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12783604#action_12783604
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ZhuGuanyin commented on MAPREDUCE-1247:
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We could make the out-of-band heartbeat thread in tasktracker as
optionally(default not start the thread through a configurable parameter),
small cluster (running small jobs) are not needed. The additional thread is
very usefull for the cluster running large jobs. Our Product hadoop cluster
became more Robustness and never fake-lost-tasktracker any more, I would
attach the patch if someone interested.
> 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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