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https://issues.apache.org/jira/browse/HDFS-12681?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16253029#comment-16253029
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Chris Douglas commented on HDFS-12681:
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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]
earlier.
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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