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From "Andrew Wang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-6492) Support create-time xattrs and atomically setting multiple xattrs
Date Fri, 06 Jun 2014 01:36:01 GMT

    [ https://issues.apache.org/jira/browse/HDFS-6492?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14019498#comment-14019498

Andrew Wang commented on HDFS-6492:

Hi [~hitliuyi], thanks for taking a look,

Yea, I'd like to add a {{List<XAttr}} field to OP_MKDIR and OP_ADD. The idea here is that
we can be assured that a file will have the xattrs even in the presence of failures. With
separate ops, the NN might fail between creating a file and then setting xattrs, leading to
the situations I mentioned.

I'll note that other RPCs do log multiple ops, like create with overwrite and mkdirs, and
thus I believe are not atomic. That feels more okay, since it's a user operation that needs
to be cleaned up by the user, but here we'd have a messy system operation that *we'd* have
to clean up. I'd prefer to avoid making such a mess in the first place ;)

> Support create-time xattrs and atomically setting multiple xattrs
> -----------------------------------------------------------------
>                 Key: HDFS-6492
>                 URL: https://issues.apache.org/jira/browse/HDFS-6492
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: namenode
>    Affects Versions: 3.0.0
>            Reporter: Andrew Wang
>            Assignee: Andrew Wang
> Ongoing work in HDFS-6134 requires being able to set system namespace extended attributes
at create and mkdir time, as well as being able to atomically set multiple xattrs at once.
There's currently no need to expose this functionality in the client API, so let's not unless
we have to.

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