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https://issues.apache.org/jira/browse/HDFS-14718?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16904511#comment-16904511
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Wei-Chiu Chuang commented on HDFS-14718:
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There are two things that should get considered:
(1) does it break existing applications? TreeMap and HashMap are different in
that the output may be in different order. I don't we ever specified the order
so this isn't an incompatible change.
(2) performance. which one is more performant if you list a million files?
> HttpFS: Sort response by key names as WebHDFS does
> --------------------------------------------------
>
> Key: HDFS-14718
> URL: https://issues.apache.org/jira/browse/HDFS-14718
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: httpfs
> Reporter: Siyao Meng
> Assignee: Siyao Meng
> Priority: Major
>
> *Example*
> See description of HDFS-14665 for an example of LISTSTATUS.
> *Analysis*
> WebHDFS is [using a
> TreeMap|https://github.com/apache/hadoop/blob/99bf1dc9eb18f9b4d0338986d1b8fd2232f1232f/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/web/JsonUtil.java#L120]
> to serialize HdfsFileStatus, while HttpFS [uses a
> LinkedHashMap|https://github.com/apache/hadoop/blob/6fcc5639ae32efa5a5d55a6b6cf23af06fc610c3/hadoop-hdfs-project/hadoop-hdfs-httpfs/src/main/java/org/apache/hadoop/fs/http/server/FSOperations.java#L107]
> to serialize FileStatus.
> *Questions*
> Why the difference? Is this intentional?
> - I looked into the Git history. It seems it's simply because WebHDFS uses
> TreeMap from the beginning; and HttpFS uses LinkedHashMap from the beginning.
> It is not only limited to LISTSTATUS, but ALL other request's JSON
> serialization.
> Now the real question: Could/Should we replace ALL LinkedHashMap into TreeMap
> in HttpFS serialization in FSOperations class?
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