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Posted to common-issues@hadoop.apache.org by "Steve Loughran (JIRA)" <ji...@apache.org> on 2018/02/05 18:38:00 UTC
[jira] [Commented] (HADOOP-15209) PoC: DistCp to eliminate needless
deletion of files under deleted directories
[ https://issues.apache.org/jira/browse/HADOOP-15209?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16352741#comment-16352741 ]
Steve Loughran commented on HADOOP-15209:
-----------------------------------------
HADOOP-15209 patch 001
this builds up a set of paths which have have been deleted.
bug: its broken, as shown by test failures. I know the problem, but HADOOP-15208 shows my plan: move this out of distcp and experiment elsewhere.
> PoC: DistCp to eliminate needless deletion of files under 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
> Priority: Major
> Attachments: HADOOP-15209-001.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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