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https://issues.apache.org/jira/browse/HADOOP-15281?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16762757#comment-16762757
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Andrew Olson commented on HADOOP-15281:
---------------------------------------
Thanks for accepting the patch. We don't have a concrete need for it in 2.x at
this time, but I think the code changes should merge in mostly cleanly.
> Distcp to add no-rename copy option
> -----------------------------------
>
> Key: HADOOP-15281
> URL: https://issues.apache.org/jira/browse/HADOOP-15281
> Project: Hadoop Common
> Issue Type: Improvement
> Components: tools/distcp
> Affects Versions: 3.0.0
> Reporter: Steve Loughran
> Assignee: Andrew Olson
> Priority: Major
> Fix For: 3.2.1, 3.1.3
>
> Attachments: HADOOP-15281-001.patch, HADOOP-15281-002.patch,
> HADOOP-15281-003.patch, HADOOP-15281-004.patch
>
>
> Currently Distcp uploads a file by two strategies
> # append parts
> # copy to temp then rename
> option 2 executes the following sequence in {{promoteTmpToTarget}}
> {code}
> if ((fs.exists(target) && !fs.delete(target, false))
> || (!fs.exists(target.getParent()) && !fs.mkdirs(target.getParent()))
> || !fs.rename(tmpTarget, target)) {
> throw new IOException("Failed to promote tmp-file:" + tmpTarget
> + " to: " + target);
> }
> {code}
> For any object store, that's a lot of HTTP requests; for S3A you are looking
> at 12+ requests and an O(data) copy call.
> This is not a good upload strategy for any store which manifests its output
> atomically at the end of the write().
> Proposed: add a switch to write directly to the dest path, which can be
> supplied as either a conf option (distcp.direct.write) or a CLI option
> (-direct).
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