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From "Steve Loughran (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-14236) S3Guard: S3AFileSystem::rename() should move non-listed sub-directory entries in metadata store
Date Wed, 29 Mar 2017 16:25:41 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-14236?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15947439#comment-15947439
] 

Steve Loughran commented on HADOOP-14236:
-----------------------------------------

As mingliang has just pointed out to me, s3a's {{mkdirs()}} doesn't delete mock parent paths,
so 
{{mkdir /a}}  creates "a/"
{{mkdir /a/b}} creates "a/b/" and leaves "a/"
only in the {{reate(a/b/c.txt)}} will a/ and b/ get deleted

FS contract tests need to verify empty directory create through sequence of 

{code}
mkdir a
mkdir a/b
mkdir a/b/c
rename (a, d)
assertIsDir(d/b)
assertIsDir(d/b/c)
{code}

> S3Guard: S3AFileSystem::rename() should move non-listed sub-directory entries in metadata
store
> -----------------------------------------------------------------------------------------------
>
>                 Key: HADOOP-14236
>                 URL: https://issues.apache.org/jira/browse/HADOOP-14236
>             Project: Hadoop Common
>          Issue Type: Sub-task
>          Components: fs/s3
>            Reporter: Mingliang Liu
>            Assignee: Mingliang Liu
>            Priority: Critical
>         Attachments: HADOOP-14236-HADOOP-13345.000.patch, HADOOP-14236-HADOOP-13345.001.patch,
HADOOP-14236-HADOOP-13345.002.patch
>
>
> After running integration test {{ITestS3AFileSystemContract}}, I found the following
items are not cleaned up in DynamoDB:
> {code}
> parent=/mliu-s3guard/user/mliu/s3afilesystemcontract/testRenameDirectoryAsExisting/dir,
child=subdir
> parent=/mliu-s3guard/user/mliu/s3afilesystemcontract/testRenameDirectoryAsExistingNew/newdir/subdir,
child=file2
> {code}
> At first I thought it’s similar to [HADOOP-14226] or [HADOOP-14227], and we need to
be careful when cleaning up test data.
> Then I found it’s a bug(?) in the code of integrating S3Guard with S3AFileSystem: for
rename we miss sub-directory items to put (dest) and delete (src). The reason is that in S3A,
we delete those fake directory objects if they are not necessary, e.g. non-empty. So when
we list the objects to rename, the object summaries will only return _file_ objects. This
has two consequences after rename:
> #  there will be left items for src path in metadata store - left-overs will confuse
{{get(Path)}} which should return null
> # we are not persisting the whole subtree for dest path to metadata store - this will
break the DynamoDBMetadataStore invariant: _if a path exists, all its ancestors will also
exist in the table_.
> UPDATE: modified test case {{ITestS3AFileSystemContract:: testRenameDirectoryAsExistingDirectory()}}
will fail w/o this patch; it passes w/ this patch. If the test case makes sense, the proposal
follows.
> Existing tests are not complaining about this though. If this is a real bug, let’s
address it here.



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