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https://issues.apache.org/jira/browse/HADOOP-13884?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Steve Loughran updated HADOOP-13884:
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Description:
before doing a create(), s3a does a getFileStatus() to make sure there isn't a
directory there, and, if overwrite=false, that there isn't a file.
Because S3 caches negative HEAD/GET requests, if there isn't a file, then even
after the PUT, a later GET/HEAD may return 404; we are generating create
consistency where none need exist.
when overwrite=true we don't care whether the file exists or not, only that the
path isn't a directory. So we can just do the HEAD path +"/' and the LIST
calls, skipping the {{HEAD path}}. This will save an HTTP round trip of a few
hundred millis, and ensure that there's no 404 cached in the S3 front end for
later callers
was:
before doing a create(), s3a does a getFileStatus() to make sure there isn't a
directory there, and, if overwrite=false, that there isn't a file.
Because S3 caches negative HEAD/GET requests, if there isn't a file, then even
after the PUT, a later GET/HEAD may return 404; we are generating create
consistency where none need exist.
when overwrite=true we don't care whether the file exists or not, only that the
path isn't a directory. So we can just to the HEAD path +"/' and the LIST
calls, skipping the {{HEAD path}}. This will save an HTTP round trip of a few
hundred millis, and ensure that there's no 404 cached in the S3 front end for
later callers
> s3a create(overwrite=true) to only look for dir/ and list entries, not file
> ---------------------------------------------------------------------------
>
> Key: HADOOP-13884
> URL: https://issues.apache.org/jira/browse/HADOOP-13884
> Project: Hadoop Common
> Issue Type: Sub-task
> Components: fs/s3
> Affects Versions: 2.9.0
> Reporter: Steve Loughran
> Priority: Minor
>
> before doing a create(), s3a does a getFileStatus() to make sure there isn't
> a directory there, and, if overwrite=false, that there isn't a file.
> Because S3 caches negative HEAD/GET requests, if there isn't a file, then
> even after the PUT, a later GET/HEAD may return 404; we are generating create
> consistency where none need exist.
> when overwrite=true we don't care whether the file exists or not, only that
> the path isn't a directory. So we can just do the HEAD path +"/' and the LIST
> calls, skipping the {{HEAD path}}. This will save an HTTP round trip of a few
> hundred millis, and ensure that there's no 404 cached in the S3 front end for
> later callers
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