An error occurs when did long time processing

Dear all,  when I use my program to do small data processing, it works well. But when I use the program to do the longer time processing, it throws the errors. Does anyone have any idea why this happens. the errors are shows as follows:

ERROR: org.apache.hadoop.hdfs.server.namenode.LeaseExpiredException: No lease on /user/wangzk/genesnp/output2/_temporary/_attempt_201005101835_0045_r_000000_1/part-00000 File does not exist. Holder DFSClient_attempt_201005101835_0045_r_000000_1 does not have any open files.
       at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.checkLease(FSNamesystem.java:1332)
  at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.checkLease(FSNamesystem.java:1323)
  at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.getAdditionalBlock(FSNamesystem.java:1251)
  at org.apache.hadoop.hdfs.server.namenode.NameNode.addBlock(NameNode.java:422)
     at sun.reflect.GeneratedMethodAccessor127.invoke(Unknown Source)
   at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
   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)

org.apache.hadoop.ipc.RemoteException: org.apache.hadoop.hdfs.server.namenode.LeaseExpiredException: No lease on /user/wangzk/genesnp/output2/_temporary/_attempt_201005101835_0045_r_000000_1/part-00000 File does not exist. Holder DFSClient_attempt_201005101835_0045_r_000000_1 does not have any open files.
   at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.checkLease(FSNamesystem.java:1332)
  at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.checkLease(FSNamesystem.java:1323)
  at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.getAdditionalBlock(FSNamesystem.java:1251)
  at org.apache.hadoop.hdfs.server.namenode.NameNode.addBlock(NameNode.java:422)
     at sun.reflect.GeneratedMethodAccessor127.invoke(Unknown Source)
   at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
   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)

  at org.apache.hadoop.ipc.Client.call(Client.java:740)
      at org.apache.hadoop.ipc.RPC$Invoker.invoke(RPC.java:220)
  at $Proxy1.addBlock(Unknown Source)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
     at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
   at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
   at java.lang.reflect.Method.invoke(Method.java:597)
        at org.apache.hadoop.io.retry.RetryInvocationHandler.invokeMethod(RetryInvocationHandler.java:82)
  at org.apache.hadoop.io.retry.RetryInvocationHandler.invoke(RetryInvocationHandler.java:59)
        at $Proxy1.addBlock(Unknown Source)
        at org.apache.hadoop.hdfs.DFSClient$DFSOutputStream.locateFollowingBlock(DFSClient.java:2937)
      at org.apache.hadoop.hdfs.DFSClient$DFSOutputStream.nextBlockOutputStream(DFSClient.java:2819)
     at org.apache.hadoop.hdfs.DFSClient$DFSOutputStream.access$2000(DFSClient.java:2102)
       at org.apache.hadoop.hdfs.DFSClient$DFSOutputStream$DataStreamer.run(DFSClient.java:2288)