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From "Suresh Srinivas (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-4849) Idempotent create, append and delete operations.
Date Wed, 29 May 2013 05:36:20 GMT

    [ https://issues.apache.org/jira/browse/HDFS-4849?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13669018#comment-13669018

Suresh Srinivas commented on HDFS-4849:

bq. because DFSClient.clientName includes the thread name...
How do you guarantee RPC call ID + client name is unique?

bq. The semantics of delete should be that "object does not exist after delete completes".
This seems idempotent to me.
This definition is not complete. Slightly rephrasing "uniquely identified object does not
exist after delete completes". In this regard, any deletion that identifies the object using
path, which is not unique will not work. Between two retries, if another client creates the
path being deleted, second retry could delete a file that should not be deleted. I think fileID/inodeID
recently introduced can make delete idempotent, in cases where client knows about the file
ID of the file. This will not work for deletions based on path alone.

> Idempotent create, append and delete operations.
> ------------------------------------------------
>                 Key: HDFS-4849
>                 URL: https://issues.apache.org/jira/browse/HDFS-4849
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: namenode
>    Affects Versions: 2.0.4-alpha
>            Reporter: Konstantin Shvachko
>            Assignee: Konstantin Shvachko
> create, append and delete operations can be made idempotent. This will reduce chances
for a job or other app failures when NN fails over.

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