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From "Konstantin Boudnik (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-6927) Herriot NN and DN clients should vend statistics
Date Fri, 17 Sep 2010 22:25:34 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-6927?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12910821#action_12910821
] 

Konstantin Boudnik commented on HADOOP-6927:
--------------------------------------------

{{DatanodeDescriptor}} is namesystem specific entity. Therefore it seems to be more appropriate
to expose this information via an injected API on namenode side ((NNProtocol). 

If this new API is required to be added via DNClient protocol then its every invocation will
cause a subsequent RPC call. Instead, we can have a method in NNProtocol which will expose
datanodeMap object from where a node descriptor can be received if a datanode registration
is known.

> Herriot NN and DN clients should vend statistics
> ------------------------------------------------
>
>                 Key: HADOOP-6927
>                 URL: https://issues.apache.org/jira/browse/HADOOP-6927
>             Project: Hadoop Common
>          Issue Type: Improvement
>          Components: test
>            Reporter: Al Thompson
>
> The HDFS web user interface serves useful information through dfshealth.jsp and dfsnodelist.jsp.
> The Herriot interface to the namenode and datanode (as implemented in NNClient and DNClient,
respectively) would benefit from the addition of some way to channel this information. In
the case of DNClient this can be an injected method that returns a DatanodeDescriptor relevant
to the underlying datanode.
> There seems to be no analagous NamenodeDescriptor. It may be useful to add this as a
facade to a visitor that aggregates values across the filesystem datanodes. These values are
(from dfshealth JSP):
> Configured Capacity
> DFS Used
> Non DFS Used
> DFS Remaining
> DFS Used%
> DFS Remaining%
> Live Nodes
> Dead Nodes
> Decommissioning Nodes
> Number of Under-Replicated Blocks
> Attributes reflecting the web user interface header may also be useful such as When-Started,
Version, When-Compiled, and Upgrade-Status.
> A NamenodeDescriptor would essentially "push down" the code in dfshealth web UI behind
a more general abstraction. If it is objectionable to make this class available in HDFS, perhaps
this could be packaged in a Herriot specific way.

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