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Date: Thu, 10 Sep 2009 21:26:57 -0700 (PDT)
From: "Jothi Padmanabhan (JIRA)" <jira@apache.org>
To: mapreduce-dev@hadoop.apache.org
Subject: [jira] Resolved: (MAPREDUCE-240) Improve the shuffle phase by using
 the "connection: keep-alive" and doing batch transfers of files
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     [ https://issues.apache.org/jira/browse/MAPREDUCE-240?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Jothi Padmanabhan resolved MAPREDUCE-240.
-----------------------------------------

    Resolution: Duplicate

MAPREDUCE-318 incorporated this

> Improve the shuffle phase by using the "connection: keep-alive" and doing batch transfers of files
> --------------------------------------------------------------------------------------------------
>
>                 Key: MAPREDUCE-240
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-240
>             Project: Hadoop Map/Reduce
>          Issue Type: Improvement
>            Reporter: Devaraj Das
>            Assignee: Jothi Padmanabhan
>         Attachments: hadoop-1338-v1.patch, hadoop-1338-v2.patch
>
>
> We should do transfers of map outputs at the granularity of  *total-bytes-transferred* rather than the current way of transferring a single file and then closing the connection to the server. A single TaskTracker might have a couple of map output files for a given reduce, and we should transfer multiple of them (upto a certain total size) in a single connection to the TaskTracker. Using HTTP-1.1's keep-alive connection would help since it would keep the connection open for more than one file transfer. We should limit the transfers to a certain size so that we don't hold up a jetty thread indefinitely (and cause timeouts for other clients).
> Overall, this should give us improved performance.

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