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From "Yufei Gu (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-8828) Utilize Snapshot diff report to build copy list in distcp
Date Wed, 19 Aug 2015 00:01:39 GMT

    [ https://issues.apache.org/jira/browse/HDFS-8828?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14702194#comment-14702194

Yufei Gu commented on HDFS-8828:

Hi [~jingzhao],

Thank you very much for great comments. I've uploaded a new patch 009. 
1. The new patch moves the diff report processing code and the list building code all into
the DistCpSync class, and wraps the DiffInfo EnumMap in the class DistCpSync. 
2. The new patch removes one sort operation, and modifies code to optimize function getTraverseExcludeList
with a sorted array.

> Utilize Snapshot diff report to build copy list in distcp
> ---------------------------------------------------------
>                 Key: HDFS-8828
>                 URL: https://issues.apache.org/jira/browse/HDFS-8828
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: distcp, snapshots
>            Reporter: Yufei Gu
>            Assignee: Yufei Gu
>         Attachments: HDFS-8828.001.patch, HDFS-8828.002.patch, HDFS-8828.003.patch, HDFS-8828.004.patch,
HDFS-8828.005.patch, HDFS-8828.006.patch, HDFS-8828.007.patch, HDFS-8828.008.patch, HDFS-8828.009.patch
> Some users reported huge time cost to build file copy list in distcp. (30 hours for 1.6M
files). We can leverage snapshot diff report to build file copy list including files/dirs
which are changes only between two snapshots (or a snapshot and a normal dir). It speed up
the process in two folds: 1. less copy list building time. 2. less file copy MR jobs.
> HDFS snapshot diff report provide information about file/directory creation, deletion,
rename and modification between two snapshots or a snapshot and a normal directory. HDFS-7535
synchronize deletion and rename, then fallback to the default distcp. So it still relies on
default distcp to building complete list of files under the source dir. This patch only puts
creation and modification files into the copy list based on snapshot diff report. We can minimize
the number of files to copy. 

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