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https://issues.apache.org/jira/browse/HADOOP-15209?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16399897#comment-16399897
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Aaron Fabbri commented on HADOOP-15209:
---------------------------------------
Nice work here [[email protected]]. I did a quick re-review of the latest
patch. +1 LGTM.
{noformat}
+ if (sourceChecksum != null) {
+ // iff there's a source checksum, look for one at the destination.
+ targetChecksum = targetFS.getFileChecksum(target);
+ }
{noformat}
Nice little optimization here.
I ran the hadoop-distcp unit tests and also did some manual distcp testing from
local fs to s3a. I uploaded a 4-deep directory tree of about ~350 files and
directories to two s3a subdirs. Next I deleted 3/4 of the source (local)
directory tree and ran distcp -update -delete with and without this patch.
Significantly faster (about 4x) for that phase with the patch. (1 minute 18
second wall time with patch, 5 minute 42 second w/o patch).
Still running through the unit / integration tests.. Will update in next hour
if I see any issues. I'm happy to commit this if you are ready, just shout.
> 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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