上半部分的服务器可以理解为要往zookeeper上注册的服务,下面的客户端就是用来监听这些服务上下线的.
server端
package com.buba.zkcase;
import org.apache.zookeeper.*;
public class ZKServer {
//连接的zk的地址及端口号配置
private String connectString = "hadoop102:2181,hadoop103:2181,hadoop104:2181";
//会话超时时间,单位毫秒
private int sessionTimeout = 2000;
private ZooKeeper zooKeeper = null;
private String parentNode = "/servers";
//1.获取连接
public void getConnect() throws Exception{
zooKeeper = new ZooKeeper(connectString, sessionTimeout, new Watcher() {
@Override
public void process(WatchedEvent event) {
}
});
}
//2.注册
public void regist(String hostName) throws Exception{
String create = zooKeeper.create(parentNode + "/server", hostName.getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL);//EPHEMERAL_SEQUENTIAL短暂有序的
System.out.println(hostName + "is online" + create);
}
//3.具体的业务
public void business() throws Exception{
System.out.println("具体业务");
Thread.sleep(Long.MAX_VALUE);
}
public static void main(String[] args) throws Exception{
//1.获取连接
ZKServer server = new ZKServer();
server.getConnect();
//2.注册(创建节点)
server.regist(args[0]);
//3.具体业务逻辑
server.business();
}
}
client端
package com.buba.zookeeper;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooKeeper;
import org.junit.Test;
import java.util.ArrayList;
import java.util.List;
public class ZKClient {
//连接的zk的地址及端口号配置
private String connectString = "hadoop102:2181,hadoop103:2181,hadoop104:2181";
//会话超时时间,单位毫秒
private int sessionTimeout = 2000;
private ZooKeeper zooKeeper = null;
private String parentNode = "/servers";
//1.获取连接
public void getConnect() throws Exception{
zooKeeper = new ZooKeeper(connectString, sessionTimeout, new Watcher() {
@Override
public void process(WatchedEvent event) {
try {
getServers();
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
//2.监听节点的变化
public void getServers() throws Exception{
//监听parentNode路径子节点
List<String> children = zooKeeper.getChildren(parentNode, true);
ArrayList<String> servers = new ArrayList<>();
//获取所有子节点信息
for(String child : children){
byte[] data = zooKeeper.getData(parentNode + "/" + child, false, null);
//保存信息 ip地址
servers.add(new String(data));
}
//打印数据
System.out.println(servers);
}
//3.具体的业务逻辑
public void business() throws Exception{
System.out.println("具体业务-client");
Thread.sleep(Long.MAX_VALUE);
}
public static void main(String[] args) throws Exception {
//1.获取连接
ZKClient client = new ZKClient();
client.getConnect();
//2.监听节点变化
client.getServers();
//3.实现自己的业务逻辑
client.business();
}
}
先手动在集群上创建父节点,因为要往它下面创建节点的话,父节点必须存在,不然创建不了
然后先启动客户端,然后再启动服务端,启动服务端的时候给main方法一个参数hostname
然后多起几个服务端,改变main方法参数,然后再停几个服务端,查看client控制台打印出来的信息.
我这是启动了两个服务又停了一个,它client就可以实时监听到服务端的上下线.