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https://issues.apache.org/jira/browse/HADOOP-15361?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Andras Bokor updated HADOOP-15361:
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Attachment: HADOOP-15361.04.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,
> HADOOP-15361.03.patch, HADOOP-15361.04.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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