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From "Todd Lipcon (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-6240) Rename operation is not consistent between different implementations of FileSystem
Date Mon, 14 Sep 2009 18:08:57 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-6240?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12755119#action_12755119

Todd Lipcon commented on HADOOP-6240:

bq. Is there a use case, when atomic rename replacing the existing destination is required?

I don't have an example of one where it's strictly required, but it certainly makes application
developers' lives easier. Think about the case where a distributed application uses HDFS as
the source of record for some metadata (eg there is a small text file on HDFS with some application
information). As an application developer it would be nice to simply open the file, read it,
and be sure you won't fail. Without the atomic rename-replace, the reader can hit a race where
the file has been deleted but the new version hasn't been written. Surely the application
can know about this and continually retry until it gets a valid read, but it's a bit of an

I could certainly be convinced that this kind of behavior is out of scope for HDFS and applications
should use a database or zookeeper if they need semantics like this.

> Rename operation is not consistent between different implementations of FileSystem
> ----------------------------------------------------------------------------------
>                 Key: HADOOP-6240
>                 URL: https://issues.apache.org/jira/browse/HADOOP-6240
>             Project: Hadoop Common
>          Issue Type: Bug
>          Components: fs
>            Reporter: Suresh Srinivas
>            Assignee: Suresh Srinivas
>             Fix For: 0.21.0
> The rename operation has many scenarios that are not consistently implemented across
file systems.

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