无法访问服务器的hdfs

我们访问namenode机器，namenode会给我们数据所在datanode的ip地址供我们访问数据传输服务,

但是返回的的是datanode内网的ip,我们无法根据该IP访问datanode服务器.

报错如下

2018-06-06 17:01:44,555 [main] WARN  [org.apache.hadoop.hdfs.BlockReaderFactory] - I/O error constructing remote block reader.
java.net.ConnectException: Connection timed out: no further information
	at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method)
	at sun.nio.ch.SocketChannelImpl.finishConnect(SocketChannelImpl.java:717)
	at org.apache.hadoop.net.SocketIOWithTimeout.connect(SocketIOWithTimeout.java:206)
	at org.apache.hadoop.net.NetUtils.connect(NetUtils.java:531)
	at org.apache.hadoop.hdfs.DFSClient.newConnectedPeer(DFSClient.java:3450)
	at org.apache.hadoop.hdfs.BlockReaderFactory.nextTcpPeer(BlockReaderFactory.java:777)
	at org.apache.hadoop.hdfs.BlockReaderFactory.getRemoteBlockReaderFromTcp(BlockReaderFactory.java:694)
	at org.apache.hadoop.hdfs.BlockReaderFactory.build(BlockReaderFactory.java:355)
	at org.apache.hadoop.hdfs.DFSInputStream.blockSeekTo(DFSInputStream.java:665)
	at org.apache.hadoop.hdfs.DFSInputStream.readWithStrategy(DFSInputStream.java:874)
	at org.apache.hadoop.hdfs.DFSInputStream.read(DFSInputStream.java:926)
	at java.io.DataInputStream.read(DataInputStream.java:149)
	at sun.nio.cs.StreamDecoder.readBytes(StreamDecoder.java:284)
	at sun.nio.cs.StreamDecoder.implRead(StreamDecoder.java:326)
	at sun.nio.cs.StreamDecoder.read(StreamDecoder.java:178)
	at java.io.InputStreamReader.read(InputStreamReader.java:184)
	at java.io.BufferedReader.fill(BufferedReader.java:161)
	at java.io.BufferedReader.readLine(BufferedReader.java:324)
	at java.io.BufferedReader.readLine(BufferedReader.java:389)
	at com.feiyangshop.recommendation.HdfsHandler.main(HdfsHandler.java:36)
2018-06-06 17:01:44,560 [main] WARN  [org.apache.hadoop.hdfs.DFSClient] - Failed to connect to /192.168.1.219:50010 for block, add to deadNodes and continue. java.net.ConnectException: Connection timed out: no further information
java.net.ConnectException: Connection timed out: no further information
	at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method)
	at sun.nio.ch.SocketChannelImpl.finishConnect(SocketChannelImpl.java:717)
	at org.apache.hadoop.net.SocketIOWithTimeout.connect(SocketIOWithTimeout.java:206)
	at org.apache.hadoop.net.NetUtils.connect(NetUtils.java:531)
	at org.apache.hadoop.hdfs.DFSClient.newConnectedPeer(DFSClient.java:3450)
	at org.apache.hadoop.hdfs.BlockReaderFactory.nextTcpPeer(BlockReaderFactory.java:777)

为了能够让开发机器访问到hdfs,我们可以让namenode返回给我们datanode的域名

在开发机器的hosts文件中配置datanode对应的外网ip和域名,并且在与hdfs交互的程序中添加如下代码即可

import org.apache.hadoop.conf.Configuration;

Configuration conf = new Configuration();
//设置通过域名访问datanode
conf.set("dfs.client.use.datanode.hostname", "true");