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Posted to hdfs-issues@hadoop.apache.org by "Chris Nauroth (JIRA)" <ji...@apache.org> on 2013/07/18 20:16:50 UTC

[jira] [Updated] (HDFS-4996) ClientProtocol#metaSave can be made idempotent by overwriting the output file instead of appending to it

     [ https://issues.apache.org/jira/browse/HDFS-4996?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Chris Nauroth updated HDFS-4996:
--------------------------------

    Status: Patch Available  (was: Open)
    
> ClientProtocol#metaSave can be made idempotent by overwriting the output file instead of appending to it
> --------------------------------------------------------------------------------------------------------
>
>                 Key: HDFS-4996
>                 URL: https://issues.apache.org/jira/browse/HDFS-4996
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: namenode
>    Affects Versions: 3.0.0, 2.1.0-beta
>            Reporter: Chris Nauroth
>            Assignee: Chris Nauroth
>            Priority: Minor
>         Attachments: HDFS-4996.1.patch
>
>
> {{ClientProtocol#metaSave}} opens its output file for append.  This prevents the operation from being idempotent, because retries can cause unpredictable side effects (single copy of the output vs. multiple copies).  As discussed on HDFS-4974, the operation could be made idempotent by changing this to open the file for overwrite instead of append.

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