Zookeeer笔记（5）——分布式应用系统服务器上下线动态感知程序开发

1 客户端能实时洞察服务器上下线的情况

2 服务端程序

//DistributedServer.java

package demo2;

import org.apache.zookeeper.*;

import java.io.IOException;

public class DistributedServer {
    private ZooKeeper zk = null;

    private static final String connectString = "192.168.154.131:2181,192.168.154.131:2181,192.168.154.131:2181";
    private static final int sessionTimeout = 200000;
    private static final String parentNode="/servers";


    public void getConnect() throws IOException {
        zk=new ZooKeeper(connectString, sessionTimeout, new Watcher() {
            @Override
            public void process(WatchedEvent event) {
                System.out.println(event.getType()+"---"+event.getPath());
                try{
                    zk.getChildren("/",true);
                }catch (Exception e){

                }
            }
        });
    }

    /*
    * 向zk集群注册服务器
    * */
    public void registerServer(String hostname) throws KeeperException, InterruptedException {
       String create= zk.create(parentNode+"/server",hostname.getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL);
        System.out.println(hostname+" is online..."+create);
    }

    /*
    * 业务功能
    * */
    public void handleBussiness(String hostname) throws InterruptedException {
        System.out.println(hostname+" start work......");
        Thread.sleep(Long.MAX_VALUE);
    }

    public static void main(String[] args) throws IOException, KeeperException, InterruptedException {
        //获取zk连接
        DistributedServer server=new DistributedServer();
        server.getConnect();

        //利用zk连接注册服务器信息
        server.registerServer(args[0]);

        //启动业务功能
        server.handleBussiness(args[0]);

    }

}

3 客户端程序

//DistributedClient.java

package demo2;

import org.apache.zookeeper.KeeperException;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooKeeper;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

public class DistributedClient {


    private ZooKeeper zk = null;

    private static final String connectString = "192.168.154.131:2181,192.168.154.131:2181,192.168.154.131:2181";
    private static final int sessionTimeout = 200000;
    private static final String parentNode = "/servers";

    //
    private volatile List<String> serverList;

    public void getConnect() throws IOException {
        zk = new ZooKeeper(connectString, sessionTimeout, new Watcher() {
            @Override
            public void process(WatchedEvent event) {
                try {
                    //重新更新服务器列表，并且注册了监听
                        getServerList();
                } catch (Exception e) {
                        e.printStackTrace();
                }
            }
        });
    }

    /*
    *
    * 获取服务器信息列表
    * */

    public void getServerList() throws KeeperException, InterruptedException {

        //获取服务器子节点信息，对父节点监听
        List<String> children = zk.getChildren(parentNode, true);
        List<String> servers = new ArrayList<>();
        for (String child : children) {
            //child 只是子节点名
            byte[] data = zk.getData(parentNode + "/" + child, false, null);
            servers.add(new String(data));
        }

        //把servers赋值给成员变量serverList,以提供给各业务线程使用
        serverList=servers;

        //
        System.out.println(serverList);
    }


    /*
     * 业务功能
     * */
    public void handleBussiness() throws InterruptedException {
        System.out.println(" client start work......");
        Thread.sleep(Long.MAX_VALUE);
    }

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

        //获取zk连接
        DistributedClient client = new DistributedClient();
        client.getConnect();

        //获取servers的子节点信息，从中获取服务器列表信息
        client.getServerList();

        //业务线程启动
        client.handleBussiness();

    }
}

4 效果测试