## ✌✌✌古人有云，好记性不如烂笔头，千里之行，始于足下，每日千行代码必不可少，每日总结写一写，目标大厂，满怀希望便会所向披靡，哈哈哈！！！✌✌✌
一、✌题目要求
> 动态监视服务器上下线的过程
二、✌代码实现
1.✌Server服务器类
public class Server {
private static String connectString = "hadoop151:2181,hadoop152:2181,hadoop153:2181";
private static int sessionTimeout = 2000;
private ZooKeeper zk = null;
public static void main(String[] args) throws IOException, KeeperException, InterruptedException {
args = new String[]{"hadoop153"};
Server server = new Server();
server.getConnect();
server.regist(args[0]);
server.business();
}
//连接ZooKeeper集群
private void getConnect() throws IOException {
zk = new ZooKeeper(connectString, sessionTimeout, new Watcher() {
@Override
public void process(WatchedEvent watchedEvent) {
}
});
}
//注册服务器，将主机名写入ZooKeeper中
private void regist(String hostname) throws KeeperException, InterruptedException {
String create = zk.create("/servers/server", hostname.getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL);
System.out.println(hostname + " is online" + create);
}
//业务代码
private void business() throws InterruptedException {
//保持代码不结束，监控整个过程
Thread.sleep(Long.MAX_VALUE);
}
}2.✌Client客户端类
public class Client {
private static String connectString = "hadoop151:2181,hadoop152:2181,hadoop153:2181";
private static int sessionTimeout = 2000;
private ZooKeeper zk = null;
public static void main(String[] args) throws InterruptedException, IOException, KeeperException {
Client client = new Client();
client.getConnect();
client.getServerList();
client.business();
}
//连接ZooKeeper，并实现方法
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();
}
}
});
}
//获取文件子目录文件
private void getServerList() throws KeeperException, InterruptedException {
List<String> children = zk.getChildren("/servers", true);
ArrayList<String> servers = new ArrayList<>();
for (String child : children) {
byte[] data = zk.getData("/servers/" + child, false, null);
servers.add(new String(data));
}
System.out.println(servers);
}
private void business() throws InterruptedException {
Thread.sleep(Long.MAX_VALUE);
}
}、
