title: Hadoop MultipleOutputs in Reducer with FileAlreadyExistsException
body: <p>I use MultipleOutputs in a reducer. The multiple output will write file to a folder called NewIdentities. The code is shown as below:</p>
  
  <pre><code>private MultipleOutputs&lt;Text,Text&gt; mos;
  @Override
  public void reduce(Text inputKey, Iterable&lt;Text&gt; values, Context context) throws IOException, InterruptedException {
          ......
          // output to change report
          if (ischangereport.equals("TRUE")) {
              mos.write(new Text(e.getHID()), new Text(changereport.deleteCharAt(changereport.length() - 1).toString()), "NewIdentities/");
          }
      }
  }
  
  @Override
  public void setup(Context context) {
      mos = new MultipleOutputs&lt;Text,Text&gt;(context);
  }
  
  @Override
  protected void cleanup(Context context) throws IOException, InterruptedException {
      mos.close();
  }
  </code></pre>
  
  <p>It can run previously. But when I run it today, it throws an exception as below. My hadoop version is 2.4.0.</p>
  
  <p>Error: org.apache.hadoop.fs.FileAlreadyExistsException: /CaptureOnlyMatchIndex9/TEMP/ChangeReport/NewIdentities/-r-00000 for client 192.168.71.128 already exists at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.startFileInternal(FSNamesystem.java:2297) at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.startFileInt(FSNamesystem.java:2225) at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.startFile(FSNamesystem.java:2178) at org.apache.hadoop.hdfs.server.namenode.NameNodeRpcServer.create(NameNodeRpcServer.java:520) at org.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolServerSideTranslatorPB.create(ClientNamenodeProtocolServerSideTranslatorPB.java:354) at org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos$ClientNamenodeProtocol$2.callBlockingMethod(ClientNamenodeProtocolProtos.java) at org.apache.hadoop.ipc.ProtobufRpcEngine$Server$ProtoBufRpcInvoker.call(ProtobufRpcEngine.java:585) at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:928) at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:2013) at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:2009) at java.security.AccessController.doPrivileged(Native Method) at javax.security.auth.Subject.doAs(Subject.java:415) at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1548) at org.apache.hadoop.ipc.Server$Handler.run(Server.java:2007) 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:526) at org.apache.hadoop.ipc.RemoteException.instantiateException(RemoteException.java:106) at org.apache.hadoop.ipc.RemoteException.unwrapRemoteException(RemoteException.java:73) at org.apache.hadoop.hdfs.DFSOutputStream.newStreamForCreate(DFSOutputStream.java:1604) at org.apache.hadoop.hdfs.DFSClient.create(DFSClient.java:1465) at org.apache.hadoop.hdfs.DFSClient.create(DFSClient.java:1390) at org.apache.hadoop.hdfs.DistributedFileSystem$6.doCall(DistributedFileSystem.java:394) at org.apache.hadoop.hdfs.DistributedFileSystem$6.doCall(DistributedFileSystem.java:390) at org.apache.hadoop.fs.FileSystemLinkResolver.resolve(FileSystemLinkResolver.java:81) at org.apache.hadoop.hdfs.DistributedFileSystem.create(DistributedFileSystem.java:390) at org.apache.hadoop.hdfs.DistributedFileSystem.create(DistributedFileSystem.java:334) at org.apache.hadoop.fs.FileSystem.create(FileSystem.java:906) at org.apache.hadoop.fs.FileSystem.create(FileSystem.java:887) at org.apache.hadoop.fs.FileSystem.create(FileSystem.java:784) at org.apache.hadoop.mapreduce.lib.output.TextOutputFormat.getRecordWriter(TextOutputFormat.java:132) at org.apache.hadoop.mapreduce.lib.output.MultipleOutputs.getRecordWriter(MultipleOutputs.java:475) at </p>