ZooKeeper监听服务器节点动态上下线

某分布式系统中，主节点可以有多台，可以动态上下线，任意一台客户端都能实时感知到主节点服务器的上下线。

2．需求分析，如图

服务器动态上下线

3．具体实现

（0）先在集群上创建/servers节点

[zk: localhost:2181(CONNECTED) 10] create /servers "servers"
Created /servers

（1）服务器端向Zookeeper注册代码

package com.atguigu.zkcase;

import java.io.IOException;

import org.apache.zookeeper.CreateMode;

import org.apache.zookeeper.WatchedEvent;

import org.apache.zookeeper.Watcher;

import org.apache.zookeeper.ZooKeeper;

import org.apache.zookeeper.ZooDefs.Ids;



public class DistributeServer {



private static String connectString = "hadoop102:2181,hadoop103:2181,hadoop104:2181";

private static int sessionTimeout = 2000;

private ZooKeeper zk = null;

private String parentNode = "/servers";



// 创建到zk的客户端连接

public void getConnect() throws IOException{



zk = new ZooKeeper(connectString, sessionTimeout, new Watcher() {



@Override

public void process(WatchedEvent event) {



}

});

}



// 注册服务器

public void registServer(String hostname) throws Exception{



String create = zk.create(parentNode + "/server", hostname.getBytes(), Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL);



System.out.println(hostname +" is online "+ create);

}



// 业务功能

public void business(String hostname) throws Exception{

System.out.println(hostname+" is working ...");



Thread.sleep(Long.MAX_VALUE);

}



public static void main(String[] args) throws Exception {



// 1获取zk连接

DistributeServer server = new DistributeServer();

server.getConnect();

// 2 利用zk连接注册服务器信息

server.registServer(args[0]);

// 3 启动业务功能

server.business(args[0]);

}

}

（2）客户端代码

package com.atguigu.zkcase;

import java.io.IOException;

import java.util.ArrayList;

import java.util.List;

import org.apache.zookeeper.WatchedEvent;

import org.apache.zookeeper.Watcher;

import org.apache.zookeeper.ZooKeeper;



public class DistributeClient {


private static String connectString = "hadoop102:2181,hadoop103:2181,hadoop104:2181";

private static int sessionTimeout = 2000;

private ZooKeeper zk = null;

private String parentNode = "/servers";


// 创建到zk的客户端连接

public void getConnect() throws IOException {

zk = new ZooKeeper(connectString, sessionTimeout, new Watcher() {


@Override

public void process(WatchedEvent event) {

// 再次启动监听

try {

getServerList();

} catch (Exception e) {

e.printStackTrace();

}

}

});

}


// 获取服务列表信息

public void getServerList() throws Exception {

// 1获取服务器子节点信息，并且对父节点进行监听
List<String> children = zk.getChildren(parentNode, true);

// 2存储服务器信息列表
ArrayList<String> servers = new ArrayList<>();
// 3遍历所有节点，获取节点中的主机名称信息
for (String child : children) {

    byte[] data = zk.getData(parentNode + "/" + child, false, null);
    servers.add(new String(data));

}

// 4打印服务器列表信息
System.out.println(servers);

}

// 业务功能
public void business() throws Exception{
System.out.println("client is working ...");
Thread.sleep(Long.MAX_VALUE);

}

public static void main(String[] args) throws Exception {
// 1获取zk连接
DistributeClient client = new DistributeClient();
client.getConnect();
// 2获取servers的子节点信息，从中获取服务器信息列表
client.getServerList();
// 3业务进程启动
client.business();
}

}

ZooKeeper监听服务器节点动态上下线

某分布式系统中，主节点可以有多台，可以动态上下线，任意一台客户端都能实时感知到主节点服务器的上下线。

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