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From "Chris Douglas (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-12681) Fold HdfsLocatedFileStatus into HdfsFileStatus
Date Wed, 15 Nov 2017 06:44:00 GMT

    [ https://issues.apache.org/jira/browse/HDFS-12681?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16253029#comment-16253029

Chris Douglas commented on HDFS-12681:

bq. I am trying to understand why this is returning null, could you explain why this change
caused this blockLocations to be returned null, as I was not clear with that part?
Are you observing this returning null? Or are you asking if it might?

After this change, if an application requests a mix of {{FileStatus}} and {{LocatedFileStatus}}
instances, then it can't distinguish whether it needs an RPC to fetch locations based on their
type (as in the example you cite). v05 (IIRC) of the patch is an alternative [discussed|https://issues.apache.org/jira/browse/HDFS-12681?focusedCommentId=16219657&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-16219657]

In the cases we found (though this wasn't exhaustive), clients that used locations requested
the locations in the first request (receiving {{LocatedFileStatus}}), not using 2 RPCs.

> Fold HdfsLocatedFileStatus into HdfsFileStatus
> ----------------------------------------------
>                 Key: HDFS-12681
>                 URL: https://issues.apache.org/jira/browse/HDFS-12681
>             Project: Hadoop HDFS
>          Issue Type: Bug
>            Reporter: Chris Douglas
>            Assignee: Chris Douglas
>            Priority: Minor
>             Fix For: 3.1.0
>         Attachments: HDFS-12681.00.patch, HDFS-12681.01.patch, HDFS-12681.02.patch, HDFS-12681.03.patch,
HDFS-12681.04.patch, HDFS-12681.05.patch, HDFS-12681.06.patch, HDFS-12681.07.patch, HDFS-12681.08.patch,
HDFS-12681.09.patch, HDFS-12681.10.patch
> {{HdfsLocatedFileStatus}} is a subtype of {{HdfsFileStatus}}, but not of {{LocatedFileStatus}}.
Conversion requires copying common fields and shedding unknown data. It would be cleaner and
sufficient for {{HdfsFileStatus}} to extend {{LocatedFileStatus}}.

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