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https://issues.apache.org/jira/browse/HADOOP-18184?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17743209#comment-17743209
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ASF GitHub Bot commented on HADOOP-18184:
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steveloughran commented on PR #5832:
URL: https://github.com/apache/hadoop/pull/5832#issuecomment-1636071189
HADOOP-18184. S3A prefetch unbuffer
* Lots of statistic collection with use in tests.
* s3a prefetch tests all moved to prefetch. package
* and split into caching stream and large files tests
* large files and LRU are scale
* and testRandomReadLargeFile uses small block size to reduce read overhead
* new hadoop common org.apache.hadoop.test.Sizes sizes class with predefined
sizes (from azure; not moved existing code to it yet)
Overall, the prefetch reads of the large files are slow; while it's critical
to test multi-block files, we don't need to work on the landsat csv file.
better: one of the huge tests uses it, with a small block size of 1 MB to
force lots of work.
> 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: Steve Loughran
> Priority: Minor
> Labels: pull-request-available
>
> 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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