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Posted to common-issues@hadoop.apache.org by "Andras Bokor (JIRA)" <ji...@apache.org> on 2018/04/04 14:34:00 UTC
[jira] [Updated] (HADOOP-15361) RawLocalFileSystem should use Java
nio framework for rename
[ https://issues.apache.org/jira/browse/HADOOP-15361?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Andras Bokor updated HADOOP-15361:
----------------------------------
Status: Patch Available (was: Open)
> 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
>
>
> 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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