ZooKeeper 案例-服务器动态上下线

服务器动态上下线监听

命令行客户端中删除所有测试时使用的节点，并创建servers节点

创建net.loftiest.case1.DistributeServer类，即服务端

public class DistributeServer {
    
    

    private ZooKeeper zK;

    public static void main(String[] args) throws IOException, InterruptedException, KeeperException {
    
    
        DistributeServer server = new DistributeServer();
        // 连接zk
        server.getConnect();
        //注册服务器到zk集群
        server.regist(args[0]);
        // 启动业务逻辑
        server.business();
    }

    private void business() throws InterruptedException {
    
    
        Thread.sleep(Long.MAX_VALUE);//睡眠java允许的最长时间
    }

    private void regist(String hostname) throws InterruptedException, KeeperException {
    
    
        zK.create("/servers/"+hostname,hostname.getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL);//创建上线服务器的节点 临时带序号
        System.out.println(hostname+"is online");
    }

    private void getConnect() throws IOException {
    
    
        String connectString = "Hadoop003:2181,Hadoop004:2181,Hadoop005:2181";
        int sessionTimeout=2000;

        zK = new ZooKeeper(connectString, sessionTimeout, new Watcher() {
    
    
            @Override
            public void process(WatchedEvent watchedEvent) {
    
    

            }
        });
    }
}

给server服务端创建三个方法，getConnect()，regist(args[0])，business()；

连接到zk
创建节点
线程休眠

创建net.loftiest.case1.DistributeClient类，即客户端

public class DistributeClient {
    
    

    private ZooKeeper zK;

    public static void main(String[] args) throws IOException, InterruptedException, KeeperException {
    
    
        DistributeClient client = new DistributeClient();
        //获取zk连接
        client.getConnect();
        //监听 /servers下面的节点增加和删除
        client.getServerList();
        //业务逻辑
        client.business();
    }

    private void business() throws InterruptedException {
    
    
        Thread.sleep(Long.MAX_VALUE);
    }

    private void getServerList() throws InterruptedException, KeeperException {
    
    
        List<String> children = zK.getChildren("/servers", true);//获取所有servers下的节点

        ArrayList<Object> servers = new ArrayList<>();

        for (String child : children) {
    
    //子节点data添加到list
            byte[] data = zK.getData("/servers/"+child,false,null);
            servers.add(new String(data));
        }
        System.out.println(servers);
    }

    private void getConnect() throws IOException {
    
    
        String connectString = "Hadoop003:2181,Hadoop004:2181,Hadoop005:2181";
        int sessionTimeout = 2000;
        zK = new ZooKeeper(connectString, sessionTimeout, new Watcher() {
    
    
            @Override
            public void process(WatchedEvent watchedEvent) {
    
    
				  try {
    
    
                    getServerList();
                } catch (InterruptedException e) {
    
    
                    e.printStackTrace();
                } catch (KeeperException e) {
    
    
                    e.printStackTrace();
                }
            }
        });
    }
}