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From "Steve Loughran (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HADOOP-13208) S3A listFiles(recursive=true) to do a bulk listObjects instead of walking the pseudo-tree of directories
Date Sat, 23 Jul 2016 11:43:20 GMT

     [ https://issues.apache.org/jira/browse/HADOOP-13208?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Steve Loughran updated HADOOP-13208:
------------------------------------
    Status: Patch Available  (was: Open)

The no of requests is 5+(N/5000) for the curious, where N= # of files + mock directories under
path {{P}}.

Contrast with the recursive walker, where time is something like 4* real-or-mock-directories
+ files/5000

> 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
>
>   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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