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From "Yuri Pradkin (JIRA)" <j...@apache.org>
Subject [jira] Created: (HADOOP-3212) null pointer exception while accessing secondaryname web interface (servlet dfshealth.jsp should not be served from the
Date Tue, 08 Apr 2008 19:39:24 GMT
secondary Namenode)
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null pointer exception while accessing secondaryname web interface (servlet dfshealth.jsp
should not be served from the
secondary Namenode)
-------------------------------------------------------------------------------------------------------------------------------------------

                 Key: HADOOP-3212
                 URL: https://issues.apache.org/jira/browse/HADOOP-3212
             Project: Hadoop Core
          Issue Type: Bug
          Components: dfs
    Affects Versions: 0.16.2
         Environment: Hadoop 0.16.2, and before
            Reporter: Yuri Pradkin
            Priority: Minor


when I go to the secondary namenode HTTP (dfs.secondary.http.address) in
my browser I see something like this:

        HTTP ERROR: 500
        init
        RequestURI=/dfshealth.jsp
        Powered by Jetty://

And in secondary's log I find these lines:

2008-04-02 11:26:25,357 WARN /: /dfshealth.jsp:
java.lang.NullPointerException
        at org.apache.hadoop.dfs.dfshealth_jsp.<init>(dfshealth_jsp.java:21)
        at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
        at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
        at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
        at java.lang.reflect.Constructor.newInstance(Constructor.java:539)
        at java.lang.Class.newInstance0(Class.java:373)
        at java.lang.Class.newInstance(Class.java:326)
        at org.mortbay.jetty.servlet.Holder.newInstance(Holder.java:199)
        at org.mortbay.jetty.servlet.ServletHolder.getServlet(ServletHolder.java:326)
        at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:405)
        at org.mortbay.jetty.servlet.WebApplicationHandler.dispatch(WebApplicationHandler.java:475)
        at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:567)
        at org.mortbay.http.HttpContext.handle(HttpContext.java:1565)
        at org.mortbay.jetty.servlet.WebApplicationContext.handle(WebApplicationContext.java:635)
        at org.mortbay.http.HttpContext.handle(HttpContext.java:1517)
        at org.mortbay.http.HttpServer.service(HttpServer.java:954)
        at org.mortbay.http.HttpConnection.service(HttpConnection.java:814)
        at org.mortbay.http.HttpConnection.handleNext(HttpConnection.java:981)
        at org.mortbay.http.HttpConnection.handle(HttpConnection.java:831)
        at org.mortbay.http.SocketListener.handleConnection(SocketListener.java:244)
        at org.mortbay.util.ThreadedServer.handle(ThreadedServer.java:357)
        at org.mortbay.util.ThreadPool$PoolThread.run(ThreadPool.java:534)



Responses from core-user@hadoop.apache.org:
 
------------
"dhruba Borthakur":
The secondary Namenode uses the HTTP interface to pull the fsimage from
the primary. Similarly, the primary Namenode uses the
dfs.secondary.http.address to pull the checkpointed-fsimage back from
the secondary to the primary. So, the definition of
dfs.secondary.http.address is needed.

However, the servlet dfshealth.jsp should not be served from the
secondary Namenode. This servet should be setup in such a way that only
the primary Namenode invokes this servlet.
--------------
 Konstantin Shvachko:
We do not have any secondary nn web interface as of today.
The http server is used for transferring data between the primary and the secondary.
I don't see we can display anything useful on the secondary web UI except for the
current status, config values, and the last checkpoint date/time.
--------------

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