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Date: Tue, 12 Jul 2016 15:07:20 +0000 (UTC)
From: "Steve Loughran (JIRA)" <jira@apache.org>
To: common-issues@hadoop.apache.org
Message-ID: <JIRA.12973196.1464296094000.3359.1468336040881@Atlassian.JIRA>
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Subject: [jira] [Updated] (HADOOP-13208) S3A listFiles(recursive=true) to do
 a bulk listObjects instead of walking the pseudo-tree of directories
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archived-at: Tue, 12 Jul 2016 15:07:22 -0000


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

Steve Loughran updated HADOOP-13208:
------------------------------------
    Attachment: HADOOP-13208-branch-2-009.patch

Patch 009.

# specify RemoteIterator in {{filesystem.md}}, specifically that implementations MUST return finite sequence, that a {{while(true) next();}} is a valid iteration, and cover concurrency issues.
# listing tests also grab the remote iterators returned and do the {{while(true)}} evaluation, verifying the results match.
# Fix S3AFileSystem iterators to correctly pass these new tests (the other filesystems, which don't override the default list* operations, all pass)
# javadoc all RemoteIterators in S3AFileSystem, so explaining chained operations


> 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
>
>   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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