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Zookeeper_服务器动态上下线监听案例

作者:互联网

目录

1.需求

2.需求分析

3.具体实现

4.测试


1.需求

        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。这里用客户端和服务端模拟。 (1)服务端:输入服务器hostname模拟上线,在zk集群创建节点,节点是临时节点,重启程序就表示下线了。 (2)客户端:监听zk集群的节点变化就知道服务器的上下线情况。

2.需求分析

上线创建的节点在/servers下面

3.具体实现

( 1 )先在集群上创建 /servers 节点
[zk: localhost:2181(CONNECTED) 10] create /servers "servers"
Created /servers
(2)在 Idea 中创建包名: com.atguigu.zkcase1 (3)服务器端 代码
public class DistributeServer {
    private String connectString = "hadoop102:2181,hadoop103:2181,hadoop104:2181";
    private int sessionTimeout = 2000;
    private ZooKeeper zk;

    public static void main(String[] args) throws IOException, KeeperException, InterruptedException {

        DistributeServer server = new DistributeServer();
        //1 获取zk连接
        server.getConnect();

        //2 注册服务器到zk集群
        server.regist(args[0]);

        //3 启动业务逻辑(sleep)
        server.business();
    }

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

    private void regist(String hostname) throws KeeperException, InterruptedException {
        //因为上下线,因此节点是临时的,加-e
        String create = zk.create("/servers/" + hostname, hostname.getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL);
        //打印上线信息
        System.out.println(hostname + " is online");
    }

    private void getConnect() throws IOException {
        zk = new ZooKeeper(connectString, sessionTimeout, new Watcher() {
            @Override
            public void process(WatchedEvent watchedEvent) {

            }
        });
    }
}
(4)客户端代码
public class DistributeClient {
    private String connectString = "hadoop102:2181,hadoop103:2181,hadoop104:2181";
    private int sessionTimeout = 2000;
    private ZooKeeper zk;

    public static void main(String[] args) throws IOException, KeeperException, InterruptedException {
        DistributeClient client = new DistributeClient();
        //1 获取zk连接
        client.getConnect();

        //2 监听/servers下面子节点的增加和删除
        client.getServerList();

        //3 业务逻辑(sleep)
        client.business();
    }

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

    private void getServerList() throws KeeperException, InterruptedException {
        List<String> children = zk.getChildren("/servers", true);

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

        for (String child : children) {
            //路径进行拼接
            //上面根目录已经监听了,这里就不监听了
            //第三参数是状态
            byte[] data = zk.getData("/servers/" + child, false, null);

            servers.add(new String(data));
        }

        System.out.println(servers);
    }

    private void getConnect() throws IOException {
        zk = new ZooKeeper(connectString, sessionTimeout, new Watcher() {
            @Override
            public void process(WatchedEvent watchedEvent) {
                try {
                    getServerList();
                } catch (KeeperException e) {
                    e.printStackTrace();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        });
    }
}

4.测试

1 )在 Linux 命令行上操作增加减少服务器 测试客户端代码 ( 1 )启动 DistributeClient 客户端 (2)在 hadoop102 上 zk 的客户端 /servers 目录上创建临时带序号节点
[zk: localhost:2181(CONNECTED) 1] create -e -s 
/servers/hadoop102 "hadoop102"
[zk: localhost:2181(CONNECTED) 2] create -e -s 
/servers/hadoop103 "hadoop103"
(3)观察 Idea 控制台变化
[hadoop102, hadoop103]
(4)执行删除操作
[zk: localhost:2181(CONNECTED) 8] delete 
/servers/hadoop1020000000000
(5)观察 Idea 控制台变化
[hadoop103]
2 )在 Idea 上操作增加减少服务器 ( 1 )启动 DistributeClient 客户端(如果已经启动过,不需要重启) (2)启动 DistributeServer 服务 ①点击 Edit Configuration

②在弹出的窗口中( Program arguments )输入想启动的主机,例如, hadoop102 ③回到 DistributeServer 的 main 方 法 , 右 键 , 在 弹 出 的 窗 口 中 点 击 Run “DistributeServer.main()” ④观察 DistributeServer 控制台,提示 hadoop103 is online ⑤观察 DistributeClient 控制台,输出节点信息,提示 hadoop103  已经上线

标签:节点,zk,void,Zookeeper,private,servers,2181,服务器,监听
来源: https://blog.csdn.net/weixin_43955488/article/details/122768401