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Posted to common-issues@hadoop.apache.org by "Steve Loughran (JIRA)" <ji...@apache.org> on 2019/01/14 16:28:00 UTC
[jira] [Resolved] (HADOOP-16047) Avoid expensive rename when DistCp
is writing to S3
[ https://issues.apache.org/jira/browse/HADOOP-16047?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Steve Loughran resolved HADOOP-16047.
-------------------------------------
Resolution: Duplicate
closing as duplicate...please reattach your proposal there
as noted in that one, it's not just performance: if the rename takes so long that the workers don't get their heartbeat in: disaster
> Avoid expensive rename when DistCp is writing to S3
> ---------------------------------------------------
>
> Key: HADOOP-16047
> URL: https://issues.apache.org/jira/browse/HADOOP-16047
> Project: Hadoop Common
> Issue Type: Improvement
> Components: fs/s3, tools/distcp
> Reporter: Andrew Olson
> Priority: Major
>
> When writing to an S3-based target, the temp file and rename logic in RetriableFileCopyCommand adds some unnecessary cost to the job, as the rename operation does a server-side copy + delete in S3 [1]. The renames are parallelized across all of the DistCp map tasks, so the severity is mitigated to some extent. However a configuration property to conditionally allow distributed copies to avoid that expense and write directly to the target path would improve performance considerably.
> [1] https://github.com/apache/hadoop/blob/release-3.2.0-RC1/hadoop-common-project/hadoop-common/src/site/markdown/filesystem/introduction.md#object-stores-vs-filesystems
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