org.apache.hadoop.ipc.RemoteException(java.io.IOException): File could only be replicated to 0 nodes instead of minReplication (=1). There are 1 datanode(s) running and 1 node(s) are excluded in this operation.

描述：远程使用java api往hdfs写入文件时，只能创建空文件，无内容，报错如下

org.apache.hadoop.ipc.RemoteException(java.io.IOException): File /user/23953/test could only be replicated to 0 nodes instead of minReplication (=1).  There are 1 datanode(s) running and 1 node(s) are excluded in this operation.
	at org.apache.hadoop.hdfs.server.blockmanagement.BlockManager.chooseTarget4NewBlock(BlockManager.java:1832)
	at org.apache.hadoop.hdfs.server.namenode.FSDirWriteFileOp.chooseTargetForNewBlock(FSDirWriteFileOp.java:265)
	at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.getAdditionalBlock(FSNamesystem.java:2586)
	at org.apache.hadoop.hdfs.server.namenode.NameNodeRpcServer.addBlock(NameNodeRpcServer.java:880)
	at org.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolServerSideTranslatorPB.addBlock(ClientNamenodeProtocolServerSideTranslatorPB.java:517)
	at org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos$ClientNamenodeProtocol$2.callBlockingMethod(ClientNamenodeProtocolProtos.java)
	at org.apache.hadoop.ipc.ProtobufRpcEngine$Server$ProtoBufRpcInvoker.call(ProtobufRpcEngine.java:507)
	at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:1034)
	at org.apache.hadoop.ipc.Server$RpcCall.run(Server.java:1003)
	at org.apache.hadoop.ipc.Server$RpcCall.run(Server.java:931)
	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:1926)
	at org.apache.hadoop.ipc.Server$Handler.run(Server.java:2854)
at org.apache.hadoop.ipc.Client.getRpcResponse(Client.java:1549)
at org.apache.hadoop.ipc.Client.call(Client.java:1495)
at org.apache.hadoop.ipc.Client.call(Client.java:1394)
at org.apache.hadoop.ipc.ProtobufRpcEngine$Invoker.invoke(ProtobufRpcEngine.java:232)
at org.apache.hadoop.ipc.ProtobufRpcEngine$Invoker.invoke(ProtobufRpcEngine.java:118)
at com.sun.proxy.$Proxy10.addBlock(Unknown Source)
at org.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolTranslatorPB.addBlock(ClientNamenodeProtocolTranslatorPB.java:448)
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:422)
at org.apache.hadoop.io.retry.RetryInvocationHandler$Call.invokeMethod(RetryInvocationHandler.java:165)
at org.apache.hadoop.io.retry.RetryInvocationHandler$Call.invoke(RetryInvocationHandler.java:157)
at org.apache.hadoop.io.retry.RetryInvocationHandler$Call.invokeOnce(RetryInvocationHandler.java:95)
at org.apache.hadoop.io.retry.RetryInvocationHandler.invoke(RetryInvocationHandler.java:359)
at com.sun.proxy.$Proxy11.addBlock(Unknown Source)
at org.apache.hadoop.hdfs.DataStreamer.locateFollowingBlock(DataStreamer.java:1846)
at org.apache.hadoop.hdfs.DataStreamer.nextBlockOutputStream(DataStreamer.java:1645)
at org.apache.hadoop.hdfs.DataStreamer.run(DataStreamer.java:710)

采用jps命令查看各节点都正常运行,所有端口都已打开

代码如下

package com.fly.ch03;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FSDataOutputStream;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;

import java.net.URI;

public class WriteFile {
    public static void main(String[] args) {
        try {
            Configuration conf = new Configuration();
            conf.set("dfs.replication","1");
       
            conf.set("dfs.client.use.datanode.hostname", "true");
            conf.set("fs.defaultFS","hdfs://{ip}:9000");
            conf.set("fs.hdfs.impl","org.apache.hadoop.hdfs.DistributedFileSystem");
            FileSystem fs = FileSystem.get(conf);
            byte[] buff = "test...".getBytes(); // 要写入的内容
            String filename = "test"; //要写入的文件名
            FSDataOutputStream os = fs.create(new Path(filename));
            os.write(buff,0,buff.length);
            System.out.println("Create:"+ filename);
            os.close();
            fs.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

}

原因：hadoop是以伪分布式搭建在阿里云上的，此时从名称节点获取到的数据节点地址是内网的地址自然无法访问。通过设置conf.set("dfs.client.use.datanode.hostname", "true"); 获得的则是主机名，通过主机名去访问数据节点。

解决办法：将主机名与ip地址配置到本机host文件中