Andras Bokor updated HADOOP-15361:
    Attachment: HADOOP-15361.02.patch

> 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
>            Priority: Major
>              Labels: incompatibleChange
>         Attachments: HADOOP-15361.01.patch, HADOOP-15361.02.patch
> 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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