[HADOOP-14236] S3Guard: S3AFileSystem::rename() should move non-listed sub-directory entries in metadata store

• Type: Sub-task
• Status: Resolved
• Priority: Critical
• Resolution: Fixed
• Fix Version/s: HADOOP-13345
• Component/s: fs/s3
• Target Version/s: HADOOP-13345
• Assignee: Mingliang Liu
• Reporter: Mingliang Liu
• Created: 25/Mar/17 00:06
• Updated: 31/Mar/17 04:28
• Resolved: 31/Mar/17 02:24

Description

After running integration test ITestS3AFileSystemContract, I found the following items are not cleaned up in DynamoDB:

parent=/mliu-s3guard/user/mliu/s3afilesystemcontract/testRenameDirectoryAsExisting/dir, child=subdir
parent=/mliu-s3guard/user/mliu/s3afilesystemcontract/testRenameDirectoryAsExistingNew/newdir/subdir, child=file2

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:

1. there will be left items for src path in metadata store - left-overs will confuse get(Path) which should return null
2. 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.

Issue Links

• is depended upon by: HADOOP-13998 Merge initial S3guard release into trunk
• relates to: HADOOP-14255 S3A to delete unnecessary fake directory objects in mkdirs()