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From "Zheng Shao (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HADOOP-13975) Allow DistCp to use MultiThreadedMapper
Date Fri, 24 Feb 2017 02:32:44 GMT

     [ https://issues.apache.org/jira/browse/HADOOP-13975?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Zheng Shao updated HADOOP-13975:
--------------------------------
    Attachment: HADOOP-distcp-multithreaded-mapper-branch26.7.patch

Fixed a bug in DynamicInputChunk that interferes with MultiThreadedMapper

> Allow DistCp to use MultiThreadedMapper
> ---------------------------------------
>
>                 Key: HADOOP-13975
>                 URL: https://issues.apache.org/jira/browse/HADOOP-13975
>             Project: Hadoop Common
>          Issue Type: New Feature
>          Components: tools/distcp
>    Affects Versions: 3.0.0-alpha1
>            Reporter: Zheng Shao
>            Assignee: Zheng Shao
>            Priority: Minor
>         Attachments: HADOOP-distcp-multithreaded-mapper-branch26.1.patch, HADOOP-distcp-multithreaded-mapper-branch26.2.patch,
HADOOP-distcp-multithreaded-mapper-branch26.3.patch, HADOOP-distcp-multithreaded-mapper-branch26.4.patch,
HADOOP-distcp-multithreaded-mapper-branch26.5.patch, HADOOP-distcp-multithreaded-mapper-branch26.6.patch,
HADOOP-distcp-multithreaded-mapper-branch26.7.patch, HADOOP-distcp-multithreaded-mapper-trunk.1.patch,
HADOOP-distcp-multithreaded-mapper-trunk.2.patch, HADOOP-distcp-multithreaded-mapper-trunk.3.patch,
HADOOP-distcp-multithreaded-mapper-trunk.4.patch, HADOOP-distcp-multithreaded-mapper-trunk.5.patch,
HADOOP-distcp-multithreaded-mapper-trunk.6.patch
>
>
> Although distcp allow users to control the parallelism via number of mappers, sometimes
it's desirable to run fewer mappers but more threads per mapper.  Since distcp is network
bound (either by throughput or more frequently by latency of creating connections, opening
files, reading/writing files, and closing files), this can make each mapper much more efficient.
 When WebHDFS protocol is used either as source or target, this MultiThreaded approach can
make the HTTP connection reuse (to the NameNode) more efficient as well.
> In that way, a lot of resources can be shared so we can save memory and connections to
NameNode.



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