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https://issues.apache.org/jira/browse/HADOOP-3849?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Arun C Murthy resolved HADOOP-3849.
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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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