java.net.NoRouteToHostException: No route to host

centos7环境下，启动hadoop集群时，在master节点启动集群，发现master节点的NameNode、SecondaryNameNode、JobTracker全部启动了，但是所有的slaver节点的DataNode、TaskTracker没有启动，查看某台slaver节点logs/hadoop-root-datanode-*-.log出现如下异常：

2018-06-10 01:39:42,032 ERROR org.apache.hadoop.hdfs.server.datanode.DataNode: java.io.IOException: Call to centos7-01/192.168.146.135:9000 failed on local exception: java.net.NoRouteToHostException: No route to host
    at org.apache.hadoop.ipc.Client.wrapException(Client.java:775)
    at org.apache.hadoop.ipc.Client.call(Client.java:743)
    at org.apache.hadoop.ipc.RPC$Invoker.invoke(RPC.java:220)
    at com.sun.proxy.$Proxy3.getProtocolVersion(Unknown Source)
    at org.apache.hadoop.ipc.RPC.getProxy(RPC.java:359)
    at org.apache.hadoop.ipc.RPC.getProxy(RPC.java:346)
    at org.apache.hadoop.ipc.RPC.getProxy(RPC.java:383)
    at org.apache.hadoop.ipc.RPC.waitForProxy(RPC.java:314)
    at org.apache.hadoop.ipc.RPC.waitForProxy(RPC.java:291)
    at org.apache.hadoop.hdfs.server.datanode.DataNode.startDataNode(DataNode.java:269)
    at org.apache.hadoop.hdfs.server.datanode.DataNode.<init>(DataNode.java:216)
    at org.apache.hadoop.hdfs.server.datanode.DataNode.makeInstance(DataNode.java:1283)
    at org.apache.hadoop.hdfs.server.datanode.DataNode.instantiateDataNode(DataNode.java:1238)
    at org.apache.hadoop.hdfs.server.datanode.DataNode.createDataNode(DataNode.java:1246)
    at org.apache.hadoop.hdfs.server.datanode.DataNode.main(DataNode.java:1368)
Caused by: java.net.NoRouteToHostException: No route to host
    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:404)
    at org.apache.hadoop.ipc.Client$Connection.setupIOstreams(Client.java:304)
    at org.apache.hadoop.ipc.Client$Connection.access$1700(Client.java:176)
    at org.apache.hadoop.ipc.Client.getConnection(Client.java:860)
    at org.apache.hadoop.ipc.Client.call(Client.java:720)
    ... 13 more

其原因是master无法穿透slaver的防火墙，只需要关闭所有主机的防火墙即可。

systemctl  stop  firewalld