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https://issues.apache.org/jira/browse/HADOOP-15489?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16490281#comment-16490281
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Aaron Fabbri edited comment on HADOOP-15489 at 5/25/18 6:08 AM:
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Look at S3Guard#dirListingUnion(). We used to always update MetadataStore at
the end of listStatus(). Later we changed it to only happen when
fs.s3a.metadatastore.authoritative = true.
If you set this to true you will always update MetadataStore at end of
listStatus(), but keep in mind that the short-circuit listings are not
implemented for Dynamo MS yet ([~gabor.bota] is working towards that though).
So, you would get the behavior you want for getFileStatus() (short-circuit /
skip S3) but not listStatus() etc.
There are the other listing APIs that don't update the MetadataStore, though.
was (Author: fabbri):
Look at S3Guard#dirListingUnion(). We used to always update MetadataStore at
the end of listStatus(). Later we changed it to only happen when
fs.s3a.metadatastore.authoritative = true.
If you set this to true you will always update MetadataStore at end of
listStatus(), but keep in mind that the short-circuit listings are not
implemented for Dynamo MS yet ([~gabor.bota] is working towards that though).
There are other listing APIs that don't do this, of course.
> S3Guard to self update on directory listings of S3
> --------------------------------------------------
>
> Key: HADOOP-15489
> URL: https://issues.apache.org/jira/browse/HADOOP-15489
> Project: Hadoop Common
> Issue Type: Sub-task
> Components: fs/s3
> Affects Versions: 3.1.0
> Environment: s3guard
> Reporter: Steve Loughran
> Priority: Major
>
> S3Guard updates its table on a getFileStatus call, but not on a directory
> listing.
> While this makes directory listings faster (no need to push out an update),
> it slows down subsequent queries of the files, such as a sequence of:
> {code}
> statuses = s3a.listFiles(dir)
> for (status: statuses) {
> if (status.isFile) {
> try(is = s3a.open(status.getPath())) {
> ... do something
> }
> }
> {code}
> this is because the open() is doing the getFileStatus check, even after the
> listing.
> Updating the DDB tables after a listing would give those reads a speedup,
> albeit at the expense of initiating a (bulk) update in the list call. Of
> course, we could consider making that async, though that design (essentially
> a write-buffer) would require the buffer to be checked in the reads too.
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