Time for action – killing the JobTracker

We'll first kill the JobTracker process which we should expect to impact our ability to execute MapReduce jobs but not affect the underlying HDFS filesystem.

1. Log on to the JobTracker host and kill its process.

2. Attempt to start a test MapReduce job such as Pi or WordCount:

   $ Hadoop jar wc.jar WordCount3 test.txt output
   Starting Job
   11/12/11 16:03:29 INFO ipc.Client: Retrying connect to server: /10.0.0.100:9001. Already tried 0 time(s).
   11/12/11 16:03:30 INFO ipc.Client: Retrying connect to server: /10.0.0.100:9001. Already tried 1 time(s).
   …
   11/12/11 16:03:38 INFO ipc.Client: Retrying connect to server: /10.0.0.100:9001. Already tried 9 time(s).
   java.net.ConnectException: Call to /10.0.0.100:9001 failed on connection exception: java.net.ConnectException: Connection refused
     at org.apache.hadoop.ipc.Client.wrapException(Client.java:767)
     at org.apache.hadoop.ipc.Client.call(Client.java:743)
     at org.apache.hadoop.ipc.RPC$Invoker.invoke(RPC.java:220...