解决单机 hadoop SafeModeException 异常：Cannot create file xxxxxx. Name node is in safe mode_caused by: org.apache.hadoop.hdfs.server.namenode.-优快云博客

本文介绍了一种在Hadoop单机环境下遇到的安全模式异常情况，导致无法上传文件的问题及解决办法。通过分析异常日志，发现Hadoop处于安全模式，从而阻止了文件的创建。最终通过使用命令解除安全模式解决了问题。

文章目录

1 问题说明
2 排查与解决

1 问题说明

单机 hadoop 运行环境，Java 服务调用上传文件到 hadoop 时报错，异常日志如下

org.apache.hadoop.hdfs.server.namenode.SafeModeException: Cannot create file/partFile/c38b1b95e511960d150898dfbc76d4bf/0. Name node is in safe mode.
The reported blocks 0 needs additional 18 blocks to reach the threshold 0.9990 of total blocks 19.
The number of live datanodes 1 has reached the minimum number 0. Safe mode will be turned off automatically once the thresholds have been reached. NamenodeHostName:localhost
	at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.newSafemodeException(FSNamesystem.java:1407)
	at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.checkNameNodeSafeMode(FSNamesystem.java:1395)
	at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.startFileInt(FSNamesystem.java:2280)
	at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.startFile(FSNamesystem.java:2225)
	at org.apache.hadoop.hdfs.server.namenode.NameNodeRpcServer.create(NameNodeRpcServer.java:728)
	at org.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolServerSideTranslatorPB.create(ClientNamenodeProtocolServerSideTranslatorPB.java:413)
	at org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos$ClientNamenodeProtocol$2.callBlockingMethod(ClientNamenodeProtocolProtos.java)
	at org.apache.hadoop.ipc.ProtobufRpcEngine$Server$ProtoBufRpcInvoker.call(ProtobufRpcEngine.java:447)
	at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:989)
	at org.apache.hadoop.ipc.Server$RpcCall.run(Server.java:850)
	at org.apache.hadoop.ipc.Server$RpcCall.run(Server.java:793)
	at java.security.AccessController.doPrivileged(Native Method)
	at javax.security.auth.Subject.doAs(Subject.java:422)
	at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1844)
	at org.apache.hadoop.ipc.Server$Handler.run(Server.java:2489)

	at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
	at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
	at org.apache.hadoop.ipc.RemoteException.instantiateException(RemoteException.java:121)
	at org.apache.hadoop.ipc.RemoteException.unwrapRemoteException(RemoteException.java:88)
	at org.apache.hadoop.hdfs.DFSOutputStream.newStreamForCreate(DFSOutputStream.java:270)
	at org.apache.hadoop.hdfs.DFSClient.create(DFSClient.java:1274)
	at org.apache.hadoop.hdfs.DFSClient.create(DFSClient.java:1216)
	at org.apache.hadoop.hdfs.DistributedFileSystem$8.doCall(DistributedFileSystem.java:473)
	at org.apache.hadoop.hdfs.DistributedFileSystem$8.doCall(DistributedFileSystem.java:470