zookeeper 服务端上下线，客户端感知

package pfs.y2017.m11.zookeeper.demo03;

import java.util.ArrayList;
import java.util.List;

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

public class DistributedClient {

    private static final String connectString = "192.168.1.192:2181,192.168.1.55:2181,192.168.1.28:2181";
    private static final int sessionTimeout = 2000;
    private static final String parentNode = "/servers";
    // 注意:加volatile的意义何在？
    private volatile List<String> serverList;
    private ZooKeeper zk = null;

    /**
     * 创建到zk的客户端连接
     *
     * @throws Exception
     */
    public void getConnect() throws Exception {

        zk = new ZooKeeper(connectString, sessionTimeout, new Watcher() {
            @Override
            public void process(WatchedEvent event) {
                // 收到事件通知后的回调函数（应该是我们自己的事件处理逻辑）
                try {
                    //重新更新服务器列表，并且注册了监听
                    getServerList();

                } catch (Exception e) {
                }
            }
        });

    }

    /**
     * 获取服务器信息列表
     *
     * @throws Exception
     */
    public void getServerList() throws Exception {

        // 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);

        // 先创建一个局部的list来存服务器信息
        List<String> servers = new ArrayList<String>();
        for (String child : children) {
            // child只是子节点的节点名
            byte[] data = zk.getData(parentNode + "/" + child, false, null);
            servers.add(new String(data));
        }
        // 把servers赋值给成员变量serverList，已提供给各业务线程使用
        serverList = servers;

        //打印服务器列表
        System.out.println(serverList);

    }

    /**
     * 业务功能
     *
     * @throws InterruptedException
     */
    public void handleBussiness() throws InterruptedException {
        System.out.println("client start working.....");
        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（并监听），从中获取服务器信息列表
        client.getServerList();

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

    }

}

package pfs.y2017.m11.zookeeper.demo03;

import java.util.List;

import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooDefs.Ids;
import org.apache.zookeeper.ZooKeeper;

public class DistributedServer {
    private static final String connectString = "192.168.1.192:2181,192.168.1.55:2181,192.168.1.28:2181";
    private static final int sessionTimeout = 2000;
    private static final String parentNode = "/servers";

    private ZooKeeper zk = null;

    /**
     * 创建到zk的客户端连接
     *
     * @throws Exception
     */
    public void getConnect() throws Exception {

        zk = new ZooKeeper(connectString, sessionTimeout, new Watcher() {
            @Override
            public void process(WatchedEvent event) {
                // 收到事件通知后的回调函数（应该是我们自己的事件处理逻辑）
                System.out.println(event.getType() + "---" + event.getPath());
                try {
                    zk.getChildren("/", true);
                } catch (Exception e) {
                }
            }
        });

    }

    /**
     * 向zk集群注册服务器信息
     *
     * @param hostname
     * @throws Exception
     */
    public void registerServer(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
     *
     * @throws InterruptedException
     */
    public void handleBussiness(String hostname) throws InterruptedException {
        System.out.println(hostname + "start working.....");
        Thread.sleep(Long.MAX_VALUE);
    }

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

        // 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]);

    }

}