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From "Steve Loughran (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HADOOP-15209) DistCp to eliminate needless deletion of files under already-deleted directories
Date Fri, 09 Mar 2018 18:33:01 GMT

     [ https://issues.apache.org/jira/browse/HADOOP-15209?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Steve Loughran updated HADOOP-15209:
    Status: Patch Available  (was: Open)

HADOOP-15209 patch 007

* don't worry about false from deletes. The only FS which *may* return it for bigger problems
is ftp, and ftp doesn't work as a dest for distcp
* just add it to a counter & log. At it means is that a delete of a parent dir has cut
it, but that dir is no longer in the cache.
* print cache size at the end of the run
* tests to verify using counters that there's no files copied over to the remote store. Tested
against: s3a, wasb, adl.
* tried to add counters to the delete operations, but they don't get picked up in the job
results...obviously the committer is special that way.
* and the -i ignore flag also ignores delete() failure, which makes it consistent.

> 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, HADOOP-15209-006.patch, HADOOP-15209-007.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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