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From Virajith Jalaparti <virajit...@gmail.com>
Subject Tasktracker denied communication with jobtracker
Date Tue, 21 Jun 2011 14:19:05 GMT

I am trying to setup a hadoop cluster with 7nodes with the master node also
functioning as a slave node (i.e. runs a datanode and a tasktracker along
with the namenode and jobtracker deamons). I am able to get HDFS working.
However when I try starting the tasktrackers (bin/start-mapred.sh), I get
the errors similar to the following logged in the jobtrackers log:

org.apache.hadoop.mapred.DisallowedTaskTrackerException: Tasktracker denied
communication with jobtracker: tracker_pc405.emulab.net:localhost/
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:597)
        at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:508)
        at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:959)
        at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:955)
        at java.security.AccessController.doPrivileged(Native Method)
        at javax.security.auth.Subject.doAs(Subject.java:396)
        at org.apache.hadoop.ipc.Server$Handler.run(Server.java:953)

I am not able to figure out why this happening. I think it is not a network
issue since HDFS is able to run just fine. This website
that this is because "tasktracker tries to register or communicate
the jobtracker when it does not appear on the list of included nodes, or has
been specifically excluded". However, I have included all the tasktracker
nodes in the file which is read using the "mapred.hosts" parameter.  (These
are the same nodes as the HDFS nodes and hence shouldn't be a problem)
Can anyone help me out with this?

Thanks a lot,

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