[大数据]解决Hadoop集群多次进行格式化导致DataNode不启动不能正常储存文件

格式化命令只需要在Hadoop集群初次启动前执行一次即可，后续重复启动时就不需要执行格式化了。如果再次执行格式化，集群会出错，不能正常存储文件。

报错信息如下

21/09/13 06:05:29 WARN hdfs.DFSClient: DataStreamer Exception
org.apache.hadoop.ipc.RemoteException(java.io.IOException): File /hxg.txt._COPYING_ could only be replicated to 0 nodes instead of minReplication (=1).  There are 0 datanode(s) running and no node(s) are excluded in this operation.
	at org.apache.hadoop.hdfs.server.blockmanagement.BlockManager.chooseTarget4NewBlock(BlockManager.java:1550)
	at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.getNewBlockTargets(FSNamesystem.java:3110)
	at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.getAdditionalBlock(FSNamesystem.java:3034)
	at org.apache.hadoop.hdfs.server.namenode.NameNodeRpcServer.addBlock(NameNodeRpcServer.java:723)
	at org.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolServerSideTranslatorPB.addBlock(ClientNamenodeProtocolServerSideTranslatorPB.java:492)
	at org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos$ClientNamenodeProtocol$2.callBlockingMethod(ClientNamenodeProtocolProtos.java)
	at org.apache.hadoop.ipc.ProtobufRpcEngine$Server$ProtoBufRpcInvoker.call(ProtobufRpcEngine.java:616)
	at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:969)
	at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:2049)
	at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:2045)
	at java.security.AccessController.doPrivileged(Native Method)
	at javax.security.auth.Subject.doAs(Subject.java:422)
	at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1657)
	at org.apache.hadoop.ipc.Server$Handler.run(Server.java:2043)

	at org.apache.hadoop.ipc.Client.call(Client.java:1476)
	at org.apache.hadoop.ipc.Client.call(Client.java:1407)
	at org.apache.hadoop.ipc.ProtobufRpcEngine$Invoker.invoke(ProtobufRpcEngine.java:229)
	at com.sun.proxy.$Proxy9.addBlock(Unknown Source)
	at org.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolTranslatorPB.addBlock(ClientNamenodeProtocolTranslatorPB.java:418)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.apache.hadoop.io.retry.RetryInvocationHandler.invokeMethod(RetryInvocationHandler.java:187)
	at org.apache.hadoop.io.retry.RetryInvocationHandler.invoke(RetryInvocationHandler.java:102)
	at com.sun.proxy.$Proxy10.addBlock(Unknown Source)
	at org.apache.hadoop.hdfs.DFSOutputStream$DataStreamer.locateFollowingBlock(DFSOutputStream.java:1430)
	at org.apache.hadoop.hdfs.DFSOutputStream$DataStreamer.nextBlockOutputStream(DFSOutputStream.java:1226)
	at org.apache.hadoop.hdfs.DFSOutputStream$DataStreamer.run(DFSOutputStream.java:449)
put: File /hxg.txt._COPYING_ could only be replicated to 0 nodes instead of minReplication (=1).  There are 0 datanode(s) running and no node(s) are excluded in this operation.

解决方案如下

1. 找到配置Hadoop运行产生的临时数据存储目录（配置core-site.xml文件写的目录）
2. 分别查看路径为/dfs/data/current/VERSION 和 /dfs/name/current//VERSION 中的clusterID=CID-a4437571-2de5-47be-a738-6bde78562e11
3. 对比发现namenode和datanode的clusterID不一致
4. 修改datanode里VERSION文件的clusterID 与namenode里的一致

重新启动start-dfs.sh start-yarn.sh 切记不要再格式化了

11525 SecondaryNameNode
11223 NameNode
12583 Jps
8552 NodeManager
8441 ResourceManager
12237 DataNode

启动完成上传文件测试并查看

[root@hxg220 ~]# hdfs dfs -put hxg.txt /
[root@hxg220 ~]# hdfs dfs -cat /hxg.txt