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From "Steve Loughran (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-15209) DistCp to eliminate needless deletion of files under already-deleted directories
Date Mon, 05 Mar 2018 19:25:01 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-15209?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16386597#comment-16386597
] 

Steve Loughran commented on HADOOP-15209:
-----------------------------------------

Patch 005. 
* improve copycommitter logging
* contains the checksum bypassing of HADOOP-15273, including not asking for a checksum on
the destFS if the srcFS doesn't have one. That way, if you are doing a distcp from localfs
or some store FS without checksums (wasb,...) then it will avoid the HTTP/RPC call for the
dest FS.Makes a big difference from localfs to s3

> DistCp to eliminate needless deletion of files under already-deleted directories
> --------------------------------------------------------------------------------
>
>                 Key: HADOOP-15209
>                 URL: https://issues.apache.org/jira/browse/HADOOP-15209
>             Project: Hadoop Common
>          Issue Type: Improvement
>          Components: tools/distcp
>    Affects Versions: 2.9.0
>            Reporter: Steve Loughran
>            Assignee: Steve Loughran
>            Priority: Major
>         Attachments: HADOOP-15209-001.patch, HADOOP-15209-002.patch, HADOOP-15209-003.patch,
HADOOP-15209-004.patch, HADOOP-15209-005.patch
>
>
> DistCP issues a delete(file) request even if is underneath an already deleted directory.
This generates needless load on filesystems/object stores, and, if the store throttles delete,
can dramatically slow down the delete operation.
> If the distcp delete operation can build a history of deleted directories, then it will
know when it does not need to issue those deletes.
> Care is needed here to make sure that whatever structure is created does not overload
the heap of the process.



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