原因： 防火墙没关闭
异常信息如下：

2020-01-07 22:55:12,255 [myid:2] - WARN  [QuorumPeer[myid=2](plain=/0:0:0:0:0:0:0:0:2181)(secure=disabled):QuorumCnxManager@679] - Cannot open channel to 1 at election address /192.168.31.130:3888
java.net.NoRouteToHostException: 没有到主机的路由 (Host unreachable)
        at java.net.PlainSocketImpl.socketConnect(Native Method)
        at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350)
        at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)
        at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188)
        at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
        at java.net.Socket.connect(Socket.java:606)
        at org.apache.zookeeper.server.quorum.QuorumCnxManager.connectOne(QuorumCnxManager.java:650)
        at org.apache.zookeeper.server.quorum.QuorumCnxManager.connectOne(QuorumCnxManager.java:707)
        at org.apache.zookeeper.server.quorum.QuorumCnxManager.connectAll(QuorumCnxManager.java:735)
        at org.apache.zookeeper.server.quorum.FastLeaderElection.lookForLeader(FastLeaderElection.java:910)
        at org.apache.zookeeper.server.quorum.QuorumPeer.run(QuorumPeer.java:1247)
2020-01-07 22:55:12,256 [myid:2] - INFO  [QuorumPeer[myid=2](plain=/0:0:0:0:0:0:0:0:2181)(secure=disabled):FastLeaderElection@919] - Notification time out: 6400

CentOS7 关闭防火墙命令：

systemctl stop firewalld.service #停止firewall

systemctl disable firewalld.service #禁止firewall开机启动

firewall-cmd --state #查看默认防火墙状态（关闭后显示notrunning，开启后显示running）