hdfs檔案讀寫bug2
多DFSClient同時寫同一個檔案，可能會導致以下異常。其中一個會獲取許可權寫，另外的應該會報異常。（但是獲取許可權的順序不太確定，也麼有深究）
IOExceptionLease mismatch on xxxxx owned by DFSClient_NONMAPREDUCE_230060699_8but is accessed by DFSClient_NONMAPREDUCE_1017678927_8
atorg.apache.hadoop.hdfs.server.namenode.FSNamesystem.checkLease(FSNamesystem.java:2949)
atorg.apache.hadoop.hdfs.server.namenode.FSNamesystem.analyzeFileState(FSNamesystem.java:2754)
atorg.apache.hadoop.hdfs.server.namenode.FSNamesystem.getAdditionalBlock(FSNamesystem.java:2662)
atorg.apache.hadoop.hdfs.server.namenode.NameNodeRpcServer.addBlock(NameNodeRpcServer.java:584)
atorg.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolServerSideTranslatorPB.addBlock(ClientNamenodeProtocolServerSideTranslatorPB.java:440)
atorg.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos$ClientNamenodeProtocol$2.callBlockingMethod(ClientNamenodeProtocolProtos.java)
atorg.apache.hadoop.ipc.ProtobufRpcEngine$Server$ProtoBufRpcInvoker.call(ProtobufRpcEngine.java:585)
atorg.apache.hadoop.ipc.RPC$Server.call(RPC.java:928)
atorg.apache.hadoop.ipc.Server$Handler$1.run(Server.java:2013)
atorg.apache.hadoop.ipc.Server$Handler$1.run(Server.java:2009)
atjava.security.AccessController.doPrivileged(Native Method)
atjavax.security.auth.Subject.doAs(Subject.java:415)
atorg.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1548)
atorg.apache.hadoop.ipc.Server$Handler.run(Server.java:2007)
多DFSClient同時寫同一個檔案，報出異常之後，自以為是的在異常捕獲中加入了將遠端檔案（上傳的相同檔案）刪除的程式碼。結果又出了另一個bug。一個在上傳，另一個把這個檔案刪除了。。。。
IOException---No lease on /XXXX: File does not exist. HolderDFSClient_NONMAPREDUCE_-223137850_8 does not have any open files.
atorg.apache.hadoop.hdfs.server.namenode.FSNamesystem.checkLease(FSNamesystem.java:2934)
atorg.apache.hadoop.hdfs.server.namenode.FSNamesystem.analyzeFileState(FSNamesystem.java:2754)
atorg.apache.hadoop.hdfs.server.namenode.FSNamesystem.getAdditionalBlock(FSNamesystem.java:2662)
atorg.apache.hadoop.hdfs.server.namenode.NameNodeRpcServer.addBlock(NameNodeRpcServer.java:584)
atorg.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolServerSideTranslatorPB.addBlock(ClientNamenodeProtocolServerSideTranslatorPB.java:440)
atorg.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos$ClientNamenodeProtocol$2.callBlockingMethod(ClientNamenodeProtocolProtos.java)
atorg.apache.hadoop.ipc.ProtobufRpcEngine$Server$ProtoBufRpcInvoker.call(ProtobufRpcEngine.java:585)
atorg.apache.hadoop.ipc.RPC$Server.call(RPC.java:928)
atorg.apache.hadoop.ipc.Server$Handler$1.run(Server.java:2013)
atorg.apache.hadoop.ipc.Server$Handler$1.run(Server.java:2009)
atjava.security.AccessController.doPrivileged(Native Method)
atjavax.security.auth.Subject.doAs(Subject.java:415)
atorg.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1548)
atorg.apache.hadoop.ipc.Server$Handler.run(Server.java:2007)