hadoop fs -put上传文件失败，WARN org.apache.hadoop.hdfs.server.datanode.DataNode: Problem connecting to server: master:8020

hadoop fs -put上传文件失败

报错信息：（test文件夹是已经成功建好的）

[root@master ~]# hadoop fs -put test1.txt /test
// :: WARN hdfs.DFSClient: DataStreamer Exception
org.apache.hadoop.ipc.RemoteException(java.io.IOException): File /test/test1.txt._COPYING_ could only be replicated to  nodes instead of minReplication (=).  There are  datanode(s) running and no node(s) are excluded in this operation.
        at org.apache.hadoop.hdfs.server.blockmanagement.BlockManager.chooseTarget4NewBlock(BlockManager.java:)
        at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.getNewBlockTargets(FSNamesystem.java:)
        at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.getAdditionalBlock(FSNamesystem.java:)
        at org.apache.hadoop.hdfs.server.namenode.NameNodeRpcServer.addBlock(NameNodeRpcServer.java:)
        at org.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolServerSideTranslatorPB.addBlock(ClientNamenodeProtocolServerSideTranslatorPB.java:)
        at org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos$ClientNamenodeProtocol$.callBlockingMethod(ClientNamenodeProtocolProtos.java)
        at org.apache.hadoop.ipc.ProtobufRpcEngine$Server$ProtoBufRpcInvoker.call(ProtobufRpcEngine.java:)
        at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:)
        at org.apache.hadoop.ipc.Server$Handler$.run(Server.java:)
        at org.apache.hadoop.ipc.Server$Handler$.run(Server.java:)
        at java.security.AccessController.doPrivileged(Native Method)
        at javax.security.auth.Subject.doAs(Subject.java:)
        at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:)
        at org.apache.hadoop.ipc.Server$Handler.run(Server.java:)

        at org.apache.hadoop.ipc.Client.call(Client.java:)
        at org.apache.hadoop.ipc.Client.call(Client.java:)
        at org.apache.hadoop.ipc.ProtobufRpcEngine$Invoker.invoke(ProtobufRpcEngine.java:)
        at com.sun.proxy.$Proxy10.addBlock(Unknown Source)
        at org.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolTranslatorPB.addBlock(ClientNamenodeProtocolTranslatorPB.java:)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:)
        at java.lang.reflect.Method.invoke(Method.java:)
        at org.apache.hadoop.io.retry.RetryInvocationHandler.invokeMethod(RetryInvocationHandler.java:)
        at org.apache.hadoop.io.retry.RetryInvocationHandler.invoke(RetryInvocationHandler.java:)
        at com.sun.proxy.$Proxy11.addBlock(Unknown Source)
        at org.apache.hadoop.hdfs.DFSOutputStream$DataStreamer.locateFollowingBlock(DFSOutputStream.java:)
        at org.apache.hadoop.hdfs.DFSOutputStream$DataStreamer.nextBlockOutputStream(DFSOutputStream.java:)
        at org.apache.hadoop.hdfs.DFSOutputStream$DataStreamer.run(DFSOutputStream.java:)
put: File /test/test1.txt._COPYING_ could only be replicated to  nodes instead of minReplication (=).  There are  datanode(s) running and no node(s) are excluded in this operation.

Linux报的错误是datanode节点不存在，但是去slave机器上jps发现datanode运行的好好的。然后去网上查找资料，有博客说是因为没关闭防火墙，没有访问权限， 好嘛，又去关防火墙，结果命令又不存在，因为实验室分配的机器太老了（好像是Red Hat4.x Linux3.x版本的），又吭哧吭哧装了半天命令，再查看防火墙，是关闭的啊，我真的是头疼。

然后接着找其他解决方案吧，参考资料2说可能是format次数太多，导致每次的spaceId不一致，现在想来，我确实是format了很多次，那就先来试试。

首先停止所有服务 stop-all.sh。

然后删除 core-site.xml 中hadoop.tmp.dir对应的文件夹下所有数据，注意：不是把这个文件夹也删掉！ sudo rm -rf /root/software/hadooptmp

在之后重新格式化namenode，在bin目录下 hdfs namenode -format

重新启动hadoop集群，start-all.sh

再来试试，还是不行。。

最后还是老老实实看datanode的logs，发现是无法连接上master的8020端口。

在同学的提醒下，我发现之前的hostname与ip的映射只在mater上做了，slave机器没有做，这也就造成了datanode无法连接到master，太太蠢了简直。

这也是给自己提个醒，不能太依赖网上的资料，普遍真理结合具体实际才可以顺利解决问题=_=

参考资料：

1、Failed to execute operation: No such file or directory(systemctl enable iptables.service)

2、File /input/data.txt._COPYING_ could only be replicated to 0 nodes instead of minReplication (=1)