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From "Arun C Murthy (JIRA)" <j...@apache.org>
Subject [jira] Resolved: (HADOOP-3849) MapEventsFetcherThread doesn't wait for the heartbeat-interval if it doesn't have events to fetch
Date Tue, 29 Jul 2008 17:53:32 GMT

     [ https://issues.apache.org/jira/browse/HADOOP-3849?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Arun C Murthy resolved HADOOP-3849.
-----------------------------------

    Resolution: Invalid

Invalid, FetchStatus will regulate itself to ensure it doesn't slam the JobTracker.

> MapEventsFetcherThread doesn't wait for the heartbeat-interval if it doesn't have events
to fetch
> -------------------------------------------------------------------------------------------------
>
>                 Key: HADOOP-3849
>                 URL: https://issues.apache.org/jira/browse/HADOOP-3849
>             Project: Hadoop Core
>          Issue Type: Bug
>          Components: mapred
>    Affects Versions: 0.18.0
>            Reporter: Arun C Murthy
>            Assignee: Arun C Murthy
>             Fix For: 0.19.0
>
>
> The 'notify' done by FetchStatus.getMapEvents causes the MapEventsFetcherThread to immediately
run to the JobTracker (getTaskCompletionEvents). 
> On a 3500 node cluster, I saw that each TaskTracker calls JobTracker.getTaskCompletionEvents
multiple times per-second. This caused the JobTracker's RPC queues to back-up resulting in
each RPC spending more than 120s in the queue - leading to shuffle proceeding very very slowly.

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