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https://issues.apache.org/jira/browse/HADOOP-17833?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17451803#comment-17451803
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Steve Loughran commented on HADOOP-17833:
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Tagging as a dependent on MAPREDUCE-7341 for changes in the common jar.
* statistic keys.
* rate limiter
* remote iterator feed for Tasks so incremental scheduling of manifest load and
post.
> Improve Magic Committer Performance
> -----------------------------------
>
> Key: HADOOP-17833
> URL: https://issues.apache.org/jira/browse/HADOOP-17833
> Project: Hadoop Common
> Issue Type: Improvement
> Components: fs/s3
> Affects Versions: 3.3.1
> Reporter: Steve Loughran
> Assignee: Steve Loughran
> Priority: Minor
> Labels: pull-request-available
> Time Spent: 5h 20m
> Remaining Estimate: 0h
>
> Magic committer tasks can be slow because every file created with
> overwrite=false triggers a HEAD (verify there's no file) and a LIST (that
> there's no dir). And because of delayed manifestations, it may not behave as
> expected.
> ParquetOutputFormat is one example of a library which does this.
> we could fix parquet to use overwrite=true, but (a) there may be surprises in
> other uses (b) it'd still leave the list and (c) do nothing for other formats
> call
> Proposed: createFile() under a magic path to skip all probes for file/dir at
> end of path
> Only a single task attempt Will be writing to that directory and it should
> know what it is doing. If there is conflicting file names and parts across
> tasks that won't even get picked up at this point. Oh and none of the
> committers ever check for this: you'll get the last file manifested (s3a) or
> renamed (file)
> If we skip the checks we will save 2 HTTP requests/file.
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