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From "Devaraj Das (JIRA)" <j...@apache.org>
Subject [jira] Updated: (HADOOP-5245) In TaskTracker, the notification for waking up the completion-events fetcher thread may be lost
Date Fri, 13 Feb 2009 05:25:59 GMT

     [ https://issues.apache.org/jira/browse/HADOOP-5245?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Devaraj Das updated HADOOP-5245:
--------------------------------

    Attachment: 5245.patch

Straightforward patch.

> In TaskTracker, the notification for waking up the completion-events fetcher thread may
be lost
> -----------------------------------------------------------------------------------------------
>
>                 Key: HADOOP-5245
>                 URL: https://issues.apache.org/jira/browse/HADOOP-5245
>             Project: Hadoop Core
>          Issue Type: Bug
>          Components: mapred
>            Reporter: Devaraj Das
>            Assignee: Devaraj Das
>             Fix For: 0.21.0
>
>         Attachments: 5245.patch
>
>
> In the TaskTracker, there is a completion events fetcher thread that fetches new events
from the JobTracker. Normally, the fetcher thread would sleep for heartbeatInterval amount
of time per cycle. When a reduce task asks for completion events from the corresponding TaskTracker
and the TaskTracker currently doesn't have anything to hand out, a notification is sent to
the completion events fetcher thread to wake up and fetch new events if any. Sometimes this
notification could be lost and the reduce task would be idle for a few seconds. This hurts
the performance of jobs like terasort.

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