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Date: Thu, 20 Jun 2013 05:16:23 +0000 (UTC)
From: "Suresh Srinivas (JIRA)" <jira@apache.org>
To: hdfs-dev@hadoop.apache.org
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Subject: [jira] [Created] (HDFS-4921) Create a web page to display the
 namenode features and whether they are turned on or off
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Suresh Srinivas created HDFS-4921:
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             Summary: Create a web page to display the namenode features and whether they are turned on or off
                 Key: HDFS-4921
                 URL: https://issues.apache.org/jira/browse/HDFS-4921
             Project: Hadoop HDFS
          Issue Type: Improvement
    Affects Versions: 3.0.0
            Reporter: Suresh Srinivas


The only way to determine a feature is turned on or off is to look at namenode logs or configuration. Some time when features change/modified (short circuit for example), the corresponding log message changes or goes from info to debug etc. Logs are not a reliable way to programmatically, for example in tests, to determine if a feature is turned on/off.

Also when debugging issues, routinely I have to ask for configuration to determine if the feature is turned on or off and hope that the configuration provided is the correct one loaded in the namenode.

While namenode does provide config it has loaded over http, some times either due to poor documentation or lack of understanding of configuration mechanism, people may not be able to determine if a state of the feature. I propose adding a web page that shows all that we print today in the logs, that feature status and the corresponding configuration values and feature status. This should also be made available over JMX and JMX http, just like all the other namenode webUI info, so that scripts and other programs can consume it.

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