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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:
-----------------------------------
    Attachment: HADOOP-13208-branch-2-021.patch

Steve, thank you for patch 020.  I verified all tests passing when applied to 
trunk, running against an S3 bucket in US-west-2.  Refactoring to the new 
{{Listing}} class is helpful.

I'm attaching patch 021 with some trivial changes to get us a clean pre-commit 
run:

* Correct JavaDoc parameter name that was causing a JavaDoc failure for Java 8.
* Wrap some lines that were longer than 80 characters in {{Listing}}.

> 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
>         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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