Namenode constantly using up 100% CPU 
--------------------------------------

                 Key: HADOOP-751
                 URL: http://issues.apache.org/jira/browse/HADOOP-751
             Project: Hadoop
          Issue Type: Bug
          Components: dfs
    Affects Versions: 0.8.0
            Reporter: Koji Noguchi


Trying to figure out the exact cause, but CPU load of the namenode is 
constantly 100% without any file exchanges.

.log file of the namenode showing the following exception about every 20 
seconds.

2006-11-27 16:02:07,199 INFO org.apache.hadoop.ipc.Server: IPC Server handler 5 
on 8020 call error: java.io.IOException: java.util.NoSuchElementException
java.io.IOException: java.util.NoSuchElementException
  at java.util.TreeMap$PrivateEntryIterator.nextEntry(TreeMap.java:1029)
  at java.util.TreeMap$KeyIterator.next(TreeMap.java:1058)
  at java.util.AbstractCollection.toArray(AbstractCollection.java:176)
  at 
org.apache.hadoop.dfs.DatanodeDescriptor.getBlocks(DatanodeDescriptor.java:96)
  at org.apache.hadoop.dfs.FSNamesystem.processReport(FSNamesystem.java:1446)
  at org.apache.hadoop.dfs.NameNode.blockReport(NameNode.java:506)
  at sun.reflect.GeneratedMethodAccessor11.invoke(Unknown Source)
  at 
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
  at java.lang.reflect.Method.invoke(Method.java:585)
  at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:387)
  at org.apache.hadoop.ipc.Server$Handler.run(Server.java:518)



On some of the datanodes, .log file is showing

2006-11-27 16:03:57,542 WARN org.apache.hadoop.dfs.DataNode: 
org.apache.hadoop.ipc.RemoteException: java.io.IOException: 
java.util.NoSuchElementException
  at java.util.TreeMap$PrivateEntryIterator.nextEntry(TreeMap.java:1029)
  at java.util.TreeMap$KeyIterator.next(TreeMap.java:1058)
  at java.util.AbstractCollection.toArray(AbstractCollection.java:176)
  at 
org.apache.hadoop.dfs.DatanodeDescriptor.getBlocks(DatanodeDescriptor.java:96)
  at org.apache.hadoop.dfs.FSNamesystem.processReport(FSNamesystem.java:1446)
  at org.apache.hadoop.dfs.NameNode.blockReport(NameNode.java:506)
  at sun.reflect.GeneratedMethodAccessor11.invoke(Unknown Source)
  at 
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
  at java.lang.reflect.Method.invoke(Method.java:585)
  at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:387)
  at org.apache.hadoop.ipc.Server$Handler.run(Server.java:518)

  at org.apache.hadoop.ipc.Client$Connection.run(Client.java:248)


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