一. zk admin启动默认端口是8080，如果有其他服务在用8080，那启动时就报错了，端口已被绑定

2019-06-16 10:40:29,724 [myid:] - ERROR [main:ZooKeeperServerMain@79] - Unable to start AdminServer, exiting abnormally
org.apache.zookeeper.server.admin.AdminServer$AdminServerException: Problem starting AdminServer on address 0.0.0.0, port 8080 and command URL /commands
	at org.apache.zookeeper.server.admin.JettyAdminServer.start(JettyAdminServer.java:107)
	at org.apache.zookeeper.server.ZooKeeperServerMain.runFromConfig(ZooKeeperServerMain.java:138)
	at org.apache.zookeeper.server.ZooKeeperServerMain.initializeAndRun(ZooKeeperServerMain.java:106)
	at org.apache.zookeeper.server.ZooKeeperServerMain.main(ZooKeeperServerMain.java:64)
	at org.apache.zookeeper.server.quorum.QuorumPeerMain.initializeAndRun(QuorumPeerMain.java:128)
	at org.apache.zookeeper.server.quorum.QuorumPeerMain.main(QuorumPeerMain.java:82)
Caused by: java.io.IOException: Failed to bind to /0.0.0.0:8080
	at org.eclipse.jetty.server.ServerConnector.openAcceptChannel(ServerConnector.java:346)
	at org.eclipse.jetty.server.ServerConnector.open(ServerConnector.java:308)
	at org.eclipse.jetty.server.AbstractNetworkConnector.doStart(AbstractNetworkConnector.java:80)
	at org.eclipse.jetty.server.ServerConnector.doStart(ServerConnector.java:236)
	at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:68)
	at org.eclipse.jetty.server.Server.doStart(Server.java:396)
	at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:68)
	at org.apache.zookeeper.server.admin.JettyAdminServer.start(JettyAdminServer.java:103)
	... 5 more
Caused by: java.net.BindException: 地址已在使用
	at sun.nio.ch.Net.bind0(Native Method)
	at sun.nio.ch.Net.bind(Net.java:433)
	at sun.nio.ch.Net.bind(Net.java:425)
	at sun.nio.ch.ServerSocketChannelImpl.bind(ServerSocketChannelImpl.java:223)
	at sun.nio.ch.ServerSocketAdaptor.bind(ServerSocketAdaptor.java:74)
	at org.eclipse.jetty.server.ServerConnector.openAcceptChannel(ServerConnector.java:342)
	... 12 more
Unable to start AdminServer, exiting abnormally

二. 这种情况下就去zoo.cfg文件中修改一下端口号,只要没有被其他程序占用的端口都可以

admin.serverPort=9099

三.对其他端口做一下补充

1、zookeeper有三个端口（可以修改）

1、2181

2、3888

3、2888

2、3个端口的作用

1、2181：对cline端提供服务

2、3888：选举leader使用

3、2888：集群内机器通讯使用（Leader监听此端口）

3、部署时注意

1、单机单实例，只要端口不被占用即可

2、单机伪集群（单机，部署多个实例），三个端口必须修改为组组不一样

如：myid1 : 2181,3888,2888

myid2 : 2182,3788,2788

myid3 : 2183,3688,2688

3、集群（一台机器部署一个实例）

4、集群为大于等于3个基数，如 3、5、7....,不宜太多，集群机器多了选举和数据同步耗时时长长，不稳定。目前觉得，三台选举+N台observe很不错。