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From "Steve Loughran (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-9562) Create REST interface for HDFS health data
Date Fri, 17 May 2013 16:15:17 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-9562?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13660825#comment-13660825

Steve Loughran commented on HADOOP-9562:

Clearly I was confused. My apologies. 

Anyway, I think the proposal makes sense, though the liveness tests we did for the branch-1
Linux HA on vSphere and Linux HA used an escalating set of probes.
# Pid signal -0 
# RPC, HTTP ports open
# HTTP request resolving & returning 200. (this is where returning an error code on dfs
safe mode would be invaluable, as it would avoid parsing at all)
# DFS ls operation. This is the one to verify that HDFS is really responding to requests on
the RPC channel.
# for downstream JT liveness: safe mode. state. {{setSafeMode()}} API method has proven brittle
across versions as constants for a nominally internal operation were moved round. This is
also why a safe mode HTTP page appeals to me.

I suggest then
# some JSON/XML view of DSL health, with XML actually my preference.
# a {{hdfs-live.jspx}} page that returns an HTTP error code if DFS is unhappy.

The [HappyAxis|http://svn.apache.org/repos/asf/webservices/axis/branches/explicitHeaderWork/java/webapps/axis/happyaxis.jsp]
page I wrote for Apache Axis did a lot more internal state check and diagnostics of dependencies,
env vars etc
> Create REST interface for HDFS health data
> ------------------------------------------
>                 Key: HADOOP-9562
>                 URL: https://issues.apache.org/jira/browse/HADOOP-9562
>             Project: Hadoop Common
>          Issue Type: Improvement
>          Components: fs
>    Affects Versions: 2.0.4-alpha
>            Reporter: Trevor Lorimer
>            Priority: Minor
> The HDFS health screen (dfshealth.jsp) displays basic Version, Security and Health information
concerning the NameNode, currently this information is accessible from classes in the org.apache.hadoop,hdfs.server.namenode
package and cannot be accessed outside the NameNode. This becomes prevalent if the data is
required to be displayed using a new user interface.
> The proposal is to create a REST interface to expose all the information displayed on
dfshealth.jsp using GET methods. Wrapper classes will be created to serve the data to the
REST root resource within the hadoop-hdfs project.
> This will enable the HDFS health screen information to be accessed remotely.

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