分布式应用系统服务器上下线动态感知程序开发学习笔记

分布式应用系统服务器上下线动态感知程序

package cn.itcast.bigdata.zkdist;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 = "mini1:2181,mini2:2181,mini3:2181";    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]);    }}

分布式应用系统客户端上下线动态感知程序

package cn.itcast.bigdata.zkdist;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 = "mini1:2181,mini2:2181,mini3:2181";    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();    }}