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https://issues.apache.org/jira/browse/HADOOP-18184?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17742128#comment-17742128
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ASF GitHub Bot commented on HADOOP-18184:
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steveloughran opened a new pull request, #5832:
URL: https://github.com/apache/hadoop/pull/5832
Making this a pre-requisite for vectored IO as
* helps me learn my way around the code
* I propose that the caching block stream stops its prefetching once a
vector io request has come in, maybe even free up all existing blocks.
### How was this patch tested?
in progress.
### For code changes:
- [ ] Does the title or this PR starts with the corresponding JIRA issue id
(e.g. 'HADOOP-17799. Your PR title ...')?
- [ ] Object storage: have the integration tests been executed and the
endpoint declared according to the connector-specific documentation?
- [ ] If adding new dependencies to the code, are these dependencies
licensed in a way that is compatible for inclusion under [ASF
2.0](http://www.apache.org/legal/resolved.html#category-a)?
- [ ] If applicable, have you updated the `LICENSE`, `LICENSE-binary`,
`NOTICE-binary` files?
> s3a prefetching stream to support unbuffer()
> --------------------------------------------
>
> Key: HADOOP-18184
> URL: https://issues.apache.org/jira/browse/HADOOP-18184
> Project: Hadoop Common
> Issue Type: Sub-task
> Components: fs/s3
> Affects Versions: 3.4.0
> Reporter: Steve Loughran
> Assignee: Ahmar Suhail
> Priority: Minor
>
> Apache Impala uses unbuffer() to free up all client side resources held by a
> stream, so allowing it to have a map of available (path -> stream) objects,
> retained across queries.
> This saves on having to reopen the files, with the cost of HEAD checks etc.
> S3AInputStream just closes its http connection. here there is a lot more
> state to discard, but all memory and file storage must be freed.
> until this done, ITestS3AContractUnbuffer must skip when the prefetch stream
> is used.
> its notable that the other tests don't fail, even though the stream doesn't
> implement the interface; the graceful degradation handles that. it should
> fail if the test xml resource says the stream does it, but that the stream
> capabilities say it doesn't.
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