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