服务器动态上下线监听案例
文章目录1.需求2.需求分析3.编程实现
1.先在集群上创建/servers节点2.服务器端向Zookeeper注册代码(Server)3.客户端代码(Client) 4.测试
1.在Linux命令行上 *** 作增加减少服务器2.在IDEA上 *** 增加减少服务器
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。2.需求分析 3.编程实现 1.先在集群上创建/servers节点
进入客户端后
create /servers "servers"2.服务器端向Zookeeper注册代码(Server)
package com.yingzi.zkcase1; import org.apache.zookeeper.*; import java.io.IOException; public class DistributeServer { private static int sessionTimeout = 2000; private static String connectString = "hadoop102:2181,hadoop103:2181,hadoop104:2181"; private ZooKeeper zk = null; private String parentNode = "/servers"; public static void main(String[] args) throws IOException, InterruptedException, KeeperException { 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]); //启动业务逻辑 server.business(args[0]); } //1.获取zk连接 private void getConnect() throws IOException { zk = new ZooKeeper(connectString, sessionTimeout, new Watcher() { @Override public void process(WatchedEvent event) { } }); } //2.注册服务器到zk集群 private void regist(String hostname) throws InterruptedException, KeeperException { String create = zk.create(parentNode + "/server",hostname.getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL); System.out.println(hostname + "is online" + create); } //3.启动业务逻辑 private void business(String hostname) throws InterruptedException { System.out.println(hostname + " is working ..."); Thread.sleep(Long.MAX_VALUE); } }3.客户端代码(Client)
package com.yingzi.zkcase1; 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 DistributeClient { private static String getConnectString = "hadoop102:2181,hadoop103:2181,hadoop104:2181"; private static int sessionTimeout = 2000; private ZooKeeper zk = null; private String parentNode = "/servers"; public static void main(String[] args) throws IOException, InterruptedException, KeeperException { 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(睡觉) client.business(); } //获取zk连接 private void getConnect() throws IOException { zk = new ZooKeeper(getConnectString, sessionTimeout, new Watcher() { @Override public void process(WatchedEvent event) { try { getServerList(); } catch (InterruptedException e) { e.printStackTrace(); } catch (KeeperException e) { e.printStackTrace(); } } }); } //获取服务器列表信息 public void getServerList() throws InterruptedException, KeeperException { //1.获取服务器子节点信息,并且对父节点进行监听 List4.测试 1.在Linux命令行上 *** 作增加减少服务器children = zk.getChildren(parentNode, true); //2.存储服务器信息列表 ArrayList servers = new ArrayList<>(); //3.遍历所有节点,获取节点中的主机名称信息 for (String child : children) { byte[] data = zk.getData(parentNode + "/" + child, false, null); servers.add(new String(data)); } //4.打印服务器列表信息 System.out.println(servers); } //业务逻辑 public void business() throws InterruptedException { System.out.println("client is working ..."); Thread.sleep(Long.MAX_VALUE); } }
(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
(3)观察Idea控制台变化
(4)执行删除 *** 作
(5)观察Idea控制台变化
(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 Configurations…
②在d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 d 出 的 窗 口 中 点 击 Run “DistributeServer.main()”
④观察 DistributeServer 控制台,提示 hadoop102 is working
⑤观察 DistributeClient 控制台,提示 hadoop102 已经上线
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