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https://issues.apache.org/jira/browse/HADOOP-13208?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Chris Nauroth updated HADOOP-13208:
-----------------------------------
Release Note: S3A has optimized the listFiles method by doing a bulk
listing of all entries under a path in a single S3 operation instead of
recursively walking the directory tree. The listLocatedStatus method has been
optimized by fetching results from S3 lazily as the caller traverses the
returned iterator instead of doing an eager fetch of all possible results.
> S3A listFiles(recursive=true) to do a bulk listObjects instead of walking the
> pseudo-tree of directories
> --------------------------------------------------------------------------------------------------------
>
> Key: HADOOP-13208
> URL: https://issues.apache.org/jira/browse/HADOOP-13208
> Project: Hadoop Common
> Issue Type: Sub-task
> Components: fs/s3
> Affects Versions: 2.8.0
> Reporter: Steve Loughran
> Assignee: Steve Loughran
> Priority: Minor
> Fix For: 2.9.0
>
> Attachments: HADOOP-13208-branch-2-001.patch,
> HADOOP-13208-branch-2-007.patch, HADOOP-13208-branch-2-008.patch,
> HADOOP-13208-branch-2-009.patch, HADOOP-13208-branch-2-010.patch,
> HADOOP-13208-branch-2-011.patch, HADOOP-13208-branch-2-012.patch,
> HADOOP-13208-branch-2-017.patch, HADOOP-13208-branch-2-018.patch,
> HADOOP-13208-branch-2-019.patch, HADOOP-13208-branch-2-020.patch,
> HADOOP-13208-branch-2-021.patch
>
> Original Estimate: 24h
> Remaining Estimate: 24h
>
> A major cost in split calculation against object stores turns out be listing
> the directory tree itself. That's because against S3, it takes S3A two HEADs
> and two lists to list the content of any directory path (2 HEADs + 1 list for
> getFileStatus(); the next list to query the contents).
> Listing a directory could be improved slightly by combining the final two
> listings. However, a listing of a directory tree will still be
> O(directories). In contrast, a recursive {{listFiles()}} operation should be
> implementable by a bulk listing of all descendant paths; one List operation
> per thousand descendants.
> As the result of this call is an iterator, the ongoing listing can be
> implemented within the iterator itself
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