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Date: Mon, 30 Aug 2010 02:48:57 -0400 (EDT)
From: "Liyin Liang (JIRA)" <jira@apache.org>
To: mapreduce-issues@hadoop.apache.org
Subject: [jira] Commented: (MAPREDUCE-1247) Send out-of-band heartbeat to
 avoid fake lost tasktracker
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    [ https://issues.apache.org/jira/browse/MAPREDUCE-1247?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12904091#action_12904091 ] 

Liyin Liang commented on MAPREDUCE-1247:
----------------------------------------

Hi Guanyin, our product cluster met the same problem. Would you please attach your patch file? tks.

> 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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