[jira] [Commented] (HADOOP-15489) S3Guard to self update on directory listings of S3
[
https://issues.apache.org/jira/browse/HADOOP-15489?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel=16622914#comment-16622914
]
Aaron Fabbri commented on HADOOP-15489:
---
[~ste...@apache.org] that was the original behavior and we changed it to
improve performance (those constant write-backs of listings into dynamo become
expensive). I think it is fairly close to reasonable default behavior now, but
I'd be ok with adding a non-default config knob to get the "always write back
listings" behavior. I'm thinking it might be slow though. All depends on the
access patterns.
> 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
>Assignee: Gabor Bota
>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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[jira] [Commented] (HADOOP-15489) S3Guard to self update on directory listings of S3
[
https://issues.apache.org/jira/browse/HADOOP-15489?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel=16549672#comment-16549672
]
Steve Loughran commented on HADOOP-15489:
-
OK, I see, if !auth no update. Explains why I didn't see it. I think I'd like
this even in non-auth, probably, so that if you do a getFileStatus() after it
can bypass the FS.
But: i see the risks here if something else does an update
> 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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[jira] [Commented] (HADOOP-15489) S3Guard to self update on directory listings of S3
[
https://issues.apache.org/jira/browse/HADOOP-15489?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel=16548655#comment-16548655
]
Aaron Fabbri commented on HADOOP-15489:
---
[~ste...@apache.org] see my comment above. Is there anything to do here?
> 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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[jira] [Commented] (HADOOP-15489) S3Guard to self update on directory listings of S3
[
https://issues.apache.org/jira/browse/HADOOP-15489?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel=16490281#comment-16490281
]
Aaron Fabbri commented on HADOOP-15489:
---
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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[jira] [Commented] (HADOOP-15489) S3Guard to self update on directory listings of S3
[
https://issues.apache.org/jira/browse/HADOOP-15489?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel=16484119#comment-16484119
]
Steve Loughran commented on HADOOP-15489:
-
No benchmark data here; just realised the issue exists if you are doing things
like treewalks of a filesystem not yet imported into S3Guard. Although the S3
LIST calls get the data of the descendants, the DDB table isn't updated. This
is underperformant
> 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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