试图写某事。 Java使用HDFS。
HDFS运作良好，我可以手动将文件上传到HDFS：
sudo -u hdfs hdfs dfs -put file /tmp
根据HDFS Web UI（http://nn_ip:9870），所有数据节点均正常。
但是当我尝试使用Java进行此操作时，出现异常：
Exception in thread "main" org.apache.hadoop.ipc.RemoteException(java.io.IOException): File ... could only be written to 0 of the 1 minReplication nodes. There are 3 datanode(s) running and 3 node(s) are excluded in this operation.
at org.apache.hadoop.hdfs.server.blockmanagement.BlockManager.chooseTarget4NewBlock(BlockManager.java:2103)
at org.apache.hadoop.hdfs.server.namenode.FSDirWriteFileOp.chooseTargetForNewBlock(FSDirWriteFileOp.java:287)
at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.getAdditionalBlock(FSNamesystem.java:2702)
at org.apache.hadoop.hdfs.server.namenode.NameNodeRpcServer.addBlock(NameNodeRpcServer.java:865)
at org.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolServerSideTranslatorPB.addBlock(ClientNamenodeProtocolServerSideTranslatorPB.java:550)
at org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos$ClientNamenodeProtocol$2.callBlockingMethod(ClientNamenodeProtocolProtos.java)
at org.apache.hadoop.ipc.ProtobufRpcEngine$Server$ProtoBufRpcInvoker.call(ProtobufRpcEngine.java:523)
at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:991)
at org.apache.hadoop.ipc.Server$RpcCall.run(Server.java:869)
at org.apache.hadoop.ipc.Server$RpcCall.run(Server.java:815)
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:1726)
at org.apache.hadoop.ipc.Server$Handler.run(Server.java:2675)
at org.apache.hadoop.ipc.Client.getRpcResponse(Client.java:1481)
at org.apache.hadoop.ipc.Client.call(Client.java:1427)
at org.apache.hadoop.ipc.Client.call(Client.java:1337)
at org.apache.hadoop.ipc.ProtobufRpcEngine$Invoker.invoke(ProtobufRpcEngine.java:227)
at org.apache.hadoop.ipc.ProtobufRpcEngine$Invoker.invoke(ProtobufRpcEngine.java:116)
at com.sun.proxy.$Proxy10.addBlock(Unknown Source)
at org.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolTranslatorPB.addBlock(ClientNamenodeProtocolTranslatorPB.java:440)
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:398)
at org.apache.hadoop.io.retry.RetryInvocationHandler$Call.invokeMethod(RetryInvocationHandler.java:163)
at org.apache.hadoop.io.retry.RetryInvocationHandler$Call.invoke(RetryInvocationHandler.java:155)
at org.apache.hadoop.io.retry.RetryInvocationHandler$Call.invokeOnce(RetryInvocationHandler.java:95)
at org.apache.hadoop.io.retry.RetryInvocationHandler.invoke(RetryInvocationHandler.java:335)
at com.sun.proxy.$Proxy11.addBlock(Unknown Source)
at org.apache.hadoop.hdfs.DataStreamer.locateFollowingBlock(DataStreamer.java:1733)
at org.apache.hadoop.hdfs.DataStreamer.nextBlockOutputStream(DataStreamer.java:1536)
at org.apache.hadoop.hdfs.DataStreamer.run(DataStreamer.java:658)
Java代码可以生成HDFS路径和文件，但是该文件为空：
public static void main(String[] args) throws Exception {
String hdfsuri = "hdfs://namenodeserver:8020";
String path="/user/hdfs/example1/hdfs/";
String fileName="hello.csv";
String fileContent="hello;world";
// ====== Init HDFS File System Object
Configuration conf = new Configuration();
conf.set("fs.defaultFS", hdfsuri);
conf.set("fs.hdfs.impl", org.apache.hadoop.hdfs.DistributedFileSystem.class.getName());
conf.set("fs.file.impl", org.apache.hadoop.fs.LocalFileSystem.class.getName());
System.setProperty("HADOOP_USER_NAME", "hdfs");
System.setProperty("hadoop.home.dir", "/");
FileSystem fs = FileSystem.get(URI.create(hdfsuri), conf);
//Create a path
Path hdfswritepath = new Path(newFolderPath + "/" + fileName);
//Init output stream
FSDataOutputStream outputStream=fs.create(hdfswritepath);
//Cassical output stream usage
outputStream.writeBytes(fileContent);
outputStream.close();
//Create a path
Path hdfsreadpath = new Path(newFolderPath + "/" + fileName);
//Init input stream
FSDataInputStream inputStream = fs.open(hdfsreadpath);
//Classical input stream usage
String out= IOUtils.toString(inputStream, "UTF-8");
inputStream.close();
fs.close();
}
如何解决此问题？
我看到了诸如this之类的问题。有人建议格式化namenode。但是为什么要格式化namenode？此步骤解决什么问题？我已经多次安装了HDFS。但是这个问题仍然存在。
感谢您的帮助。