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From "Chris Douglas (JIRA)" <j...@apache.org>
Subject [jira] Updated: (HADOOP-4888) Use Apache HttpClient for fetching map outputs
Date Tue, 16 Dec 2008 22:32:44 GMT

     [ https://issues.apache.org/jira/browse/HADOOP-4888?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Chris Douglas updated HADOOP-4888:
----------------------------------

    Attachment: 4888-0.patch

Preliminary patch. There are a few choices that are worth revisiting:
* This adds a HEAD to the fetch, rather than opening a connection and closing it if there's
insufficient space. While this adds a round trip, the connection will likely be reused. If
the impact is measurable, it is possible to restore the former behavior.
* The hard-coded timeouts and retries remain, but could easily be made configurable.

I haven't been able to benchmark this. Once that's possible:
* The effect of the fetch buffer size on shuffle time should be quantified
* The number of reduce copier threads should exceed the number of connection threads so the
latter may be reused. A good ratio should be arrived at experimentally.
* We should measure performance with HttpClient 3.1, too. If the data and S3 support it, we
should upgrade.

> Use Apache HttpClient for fetching map outputs
> ----------------------------------------------
>
>                 Key: HADOOP-4888
>                 URL: https://issues.apache.org/jira/browse/HADOOP-4888
>             Project: Hadoop Core
>          Issue Type: Improvement
>          Components: mapred
>            Reporter: Chris Douglas
>         Attachments: 4888-0.patch
>
>
> It's worth experimenting with the [HttpClient|http://hc.apache.org/httpclient-3.x/] library
to speed up the shuffle.

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