Andras Bokor created HADOOP-15361:
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Summary: RawLocalFileSystem should use Java nio framework for
rename
Key: HADOOP-15361
URL: https://issues.apache.org/jira/browse/HADOOP-15361
Project: Hadoop Common
Issue Type: Improvement
Reporter: Andras Bokor
Assignee: Andras Bokor
Currently RawLocalFileSystem uses a fallback logic for cross-volume renames.
The fallback logic is a copy-on-fail logic so when rename fails it copies the
source then delete it.
An additional fallback logic was needed for Windows to provide POSIX rename
behavior.
Due to the fallback logic RawLocalFileSystem does not pass the contract tests
(HADOOP-13082).
With using Java nio framework both could be eliminated since it is not platform
dependent and provides cross-volume rename.
In addition the fallback logic for Windows is not correct since Java io
overrides the destination only if the source is also a directory but
handleEmptyDstDirectoryOnWindows method checks only the destination. That means
rename allows to override a directory with a file on Windows but not on Unix.
File#renameTo and Files#move are not 100% compatible:
If the source is a directory and the destination is an empty directory
File#renameTo overrides the source but Files#move is does not. We have to use
{{StandardCopyOption.REPLACE_EXISTING}} but it overrides the destination even
if the source or the destination is a file. So to make them compatible we have
to check that the either the source or the destination is a directory before we
add the copy option.
I think the correct strategy is
* Where the contract test passed so far it should pass after this
* Where the contract test failed because of Java specific think and not
because of the fallback logic we should keep the original behavior.
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