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https://issues.apache.org/jira/browse/HDFS-7239?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14171631#comment-14171631
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Haohui Mai commented on HDFS-7239:
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The whole point of the proposed servlet is to push information that is not
suitable for JMX to UI. Because of the compatibility concerns, JMX should only
contain information that has well-defined formats and avoid duplication
whenever possible.
Since the servlet does not guarantee compatibility, it has more freedom to push
information that has a rich format (e.g., nntop), or information that can be
parsed from configuration (e.g., nameservice id) to the UI. Information that
has well-defined formats / semantics can be continued to pushed to the UI
through JMX.
> Create a servlet for HDFS UI
> ----------------------------
>
> Key: HDFS-7239
> URL: https://issues.apache.org/jira/browse/HDFS-7239
> Project: Hadoop HDFS
> Issue Type: Improvement
> Reporter: Haohui Mai
> Assignee: Haohui Mai
>
> Currently the HDFS UI gathers most of its information from JMX. There are a
> couple disadvantages:
> * JMX is also used by management tools, thus Hadoop needs to maintain
> compatibility across minor releases.
> * JMX organizes information as <key, value> pairs. The organization does not
> fit well with emerging use cases like startup progress report and nntop.
> This jira proposes to introduce a new servlet in the NN for the purpose of
> serving information to the UI.
> It should be viewed as a part of the UI. There is *no* compatibility
> guarantees for the output of the servlet.
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