hadoop错误No Route to Host连接不上yarn master:8031

Caused by: java.net.NoRouteToHostException: No Route to Host from  slave2/192.168.1.30 to master:8031 failed on socket timeout exception: java.net.NoRouteToHostEx
ception: 没有到主机的路由; For more details see:  http://wiki.apache.org/hadoop/NoRouteToHost
        at sun.reflect.GeneratedConstructorAccessor8.newInstance(Unknown Source)
        at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
        at java.lang.reflect.Constructor.newInstance(Constructor.java:422)
        at org.apache.hadoop.net.NetUtils.wrapWithMessage(NetUtils.java:791)
        at org.apache.hadoop.net.NetUtils.wrapException(NetUtils.java:757)
        at org.apache.hadoop.ipc.Client.call(Client.java:1474)
        at org.apache.hadoop.ipc.Client.call(Client.java:1401)
        at org.apache.hadoop.ipc.ProtobufRpcEngine$Invoker.invoke(ProtobufRpcEngine.java:232)
        at com.sun.proxy.$Proxy28.registerNodeManager(Unknown Source)
        at org.apache.hadoop.yarn.server.api.impl.pb.client.ResourceTrackerPBClientImpl.registerNodeManager(ResourceTrackerPBClientImpl.java:68)
        at sun.reflect.GeneratedMethodAccessor2.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:497)
        at org.apache.hadoop.io.retry.RetryInvocationHandler.invokeMethod(RetryInvocationHandler.java:187)
        at org.apache.hadoop.io.retry.RetryInvocationHandler.invoke(RetryInvocationHandler.java:102)
        at com.sun.proxy.$Proxy29.registerNodeManager(Unknown Source)
        at org.apache.hadoop.yarn.server.nodemanager.NodeStatusUpdaterImpl.registerWithRM(NodeStatusUpdaterImpl.java:262)
        at org.apache.hadoop.yarn.server.nodemanager.NodeStatusUpdaterImpl.serviceStart(NodeStatusUpdaterImpl.java:196)
        ... 6 more


Retrying connect to server: master/192.168.1.10:8031. Already tried 2 time(s); retry policy is RetryUpT
oMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1000 MILLISECONDS)
2017-01-18 19:38:53,349 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: master/192.168.1.10:8031. Already tried 3 time(s); retry policy is RetryUpT
oMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1000 MILLISECONDS)
2017-01-18 19:38:54,351 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: master/192.168.1.10:8031. Already tried 4 time(s); retry policy is RetryUpT
oMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1000 MILLISECONDS)
2017-01-18 19:39:02,367 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: master/192.168.1.10:8031. Already tried 5 time(s); retry policy is RetryUpT
oMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1000 MILLISECONDS)
2017-01-18 19:39:03,370 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: master/192.168.1.10:8031. Already tried 6 time(s); retry policy is RetryUpT
oMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1000 MILLISECONDS)
2017-01-18 19:39:04,373 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: master/192.168.1.10:8031. Already tried 7 time(s); retry policy is RetryUpT
oMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1000 MILLISECONDS)


ERROR org.apache.hadoop.yarn.server.nodemanager.NodeManager: RECEIVED SIGNAL 15: SIGTERM

解决办法：
以上尝试
各种ping，防火墙等在配置集群的时候，已经设置过了，但是后来总是报错。
后来明白，原来是因为开机启动了防火墙。所以一些服务记得开机禁用。
[mw_shl_code=bash,true]sudo systemctl disable firewalld.service
[/mw_shl_code]