[jira] Commented: (HADOOP-5444) Add atomic move option

["Hong Tang (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HADOOP-5444?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12720520#action_12720520 ] 

Hong Tang commented on HADOOP-5444:
-----------------------------------

Would the program litter partially copied directories if the command fails or interrupted by the client? 

> Add atomic move option
> ----------------------
>
>                 Key: HADOOP-5444
>                 URL: https://issues.apache.org/jira/browse/HADOOP-5444
>             Project: Hadoop Core
>          Issue Type: New Feature
>          Components: tools/distcp
>    Affects Versions: 0.18.3
>            Reporter: Richard Theige
>         Attachments: d_retries_atomic.patch
>
>
> Provide support for update to move directories/files atomically by copying the src directory to a tmp directory (with random/unique name) then move the directory to its target destination name after all subdirs/files are copied and verified.
> example option ideas
>   hadoop ... distcp -update -move src dst
> or
>   hadoop ... distcp -update -atomic src dst
> to assure file correctness at the destination, before distcp performs the  'move' at the end of the copy process, it should first perform a strong signature/cksum (e.g. MD4) on the files.
> The issue/need for this is that applications may attempt to start processing data (because files are present), prior to completion of a whole directory copy -- resulting in work against an incomplete data set.

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