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From "alan wootton (JIRA)" <j...@apache.org>
Subject [jira] Created: (HADOOP-215) New method for obtaining report of NameNode and JobTracker internals
Date Fri, 12 May 2006 20:50:08 GMT
New method for obtaining report of NameNode and JobTracker internals
--------------------------------------------------------------------

         Key: HADOOP-215
         URL: http://issues.apache.org/jira/browse/HADOOP-215
     Project: Hadoop
        Type: New Feature

  Components: mapred, dfs  
    Reporter: alan wootton
    Priority: Minor


Many weeks ago we (at shopping.com research) decided we wanted to be able to get reports from
the internals of JobTracker and NameNode. The hadoop web server provides some of this, but
we wanted a more structured output, and easier extensibility.

So, we decided to use xml, and I wrote it.

There is a very thin interface to ClientProtocol, and JobSubmissionProtocol like this:

public XmlReporter getXmlReport(String classname, String question);

The implementation (in JobTracker and NameNode ) looks like this:

public XmlReporter getXmlReport(String classname, String question)
    {
		XmlReporter reporter = XmlReporter.getInstance( classname, this,  question);
		reporter.report();
		return reporter;
    }

The idea being that you pass in some xml (question), an XmlReporter (classname) is instanciated
and passed back. 

An XmlReporter object consists of nothing more that two org.w3c.dom.Document objects (one
in the question, the other is the answer). The Writable interface, for the RPC, simply serializes
the dom tree to a string, and then parses it back to a dom tree.

Anyway, here it is. I would like for it to either make it into the code, or for me to find
anoher way. 



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