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https://issues.apache.org/jira/browse/HADOOP-15625?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16790651#comment-16790651
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Gabor Bota commented on HADOOP-15625:
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My review on patch v15:
h3. S3AInputStream.java
* Line 193 "open" and "re-open" could be constants instead of using string
literals in the code. It would be good still we started to use this string as a
parameter in a function `changeTracker.processResponse()`
h3. S3ATestUtils.java
There are two unused imports, please remove them:
* 56 import java.net.MalformedURLException;
* 59 import java.net.URL;
h3. troubleshooting_s3a.md
* Lines 718-729 and 735-747: you removed a tab from the start of those lines.
What is the reason for that?
h3. ChangeDetectionPolicy.java
* Line 333: there's no @Override annotation before {{getSource}} method.
h3. TestStreamChangeTracker.java
* Lines 90, 166, 227: Nit: 'Tracker should not have applied contraints' typo:
contraints -> constraints
h3. index.md
* The following could be emphasized more (like a warning):
{noformat}
1239 ... this option should only be used when the S3 buckets
1240 have object versioning enabled from the beginning.
{noformat}
* Nit in line 1261 {{s.s3a.change.detection.version.required}} should be
{{fs.s3a.change.detection.version.required}}
> S3A input stream to use etags to detect changed source files
> ------------------------------------------------------------
>
> Key: HADOOP-15625
> URL: https://issues.apache.org/jira/browse/HADOOP-15625
> Project: Hadoop Common
> Issue Type: Sub-task
> Components: fs/s3
> Affects Versions: 3.2.0
> Reporter: Brahma Reddy Battula
> Assignee: Brahma Reddy Battula
> Priority: Major
> Attachments: HADOOP--15625-006.patch, HADOOP-15625-001.patch,
> HADOOP-15625-002.patch, HADOOP-15625-003.patch, HADOOP-15625-004.patch,
> HADOOP-15625-005.patch, HADOOP-15625-006.patch, HADOOP-15625-007.patch,
> HADOOP-15625-008.patch, HADOOP-15625-009.patch, HADOOP-15625-010.patch,
> HADOOP-15625-011.patch, HADOOP-15625-012.patch, HADOOP-15625-013-delta.patch,
> HADOOP-15625-013.patch, HADOOP-15625-014.patch, HADOOP-15625-015.patch,
> HADOOP-15625-015.patch
>
>
> S3A input stream doesn't handle changing source files any better than the
> other cloud store connectors. Specifically: it doesn't noticed it has
> changed, caches the length from startup, and whenever a seek triggers a new
> GET, you may get one of: old data, new data, and even perhaps go from new
> data to old data due to eventual consistency.
> We can't do anything to stop this, but we could detect changes by
> # caching the etag of the first HEAD/GET (we don't get that HEAD on open with
> S3Guard, BTW)
> # on future GET requests, verify the etag of the response
> # raise an IOE if the remote file changed during the read.
> It's a more dramatic failure, but it stops changes silently corrupting things.
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