学习笔记：Zookeeper 应用案例(上下线动态感知)
1、Zookeeper 應(yīng)用案例(上下線動態(tài)感知)
8.1 案例1——服務(wù)器上下線動態(tài)感知
8.1.1 需求描述
某分布式系統(tǒng)中，主節(jié)點可以有多臺，可以動態(tài)上下線
任意一臺客戶端都能實時感知到主節(jié)點服務(wù)器的上下線
8.1.2 設(shè)計思路
8.1.3 代碼開發(fā)
1、客戶端實現(xiàn)
package cn.com.toto.zkonlineoroffline; ? import java.util.ArrayList; import java.util.List; ? import org.apache.zookeeper.WatchedEvent; import org.apache.zookeeper.Watcher; import org.apache.zookeeper.ZooKeeper; ? public class DistributedClient { ??? private static final String connectString = "192.168.106.80:2181,192.168.106.81:2181,192.168.106.82:2181"; ??? private static final int sessionTimeout = 2000; ???? private static final String parentNode = "/servers"; ???? // 注意:加volatile的意義何在？ ???? private volatile List<String> serverList; ???? private ZooKeeper zk = null; ? ???? /** ???? ?* 創(chuàng)建到zk的客戶端連接 ???? ?* ???? ?* @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調(diào)函數(shù)（應(yīng)該是我們自己的事件處理邏輯） ?????????????????? try { ?????????????????????? //重新更新服務(wù)器列表，并且注冊了監(jiān)聽 ?????????????????????? getServerList(); ? ?????????????????? } catch (Exception e) { ?????????????????? } ????????????? } ???????? }); ???? } ? ???? /** ???? ?* 獲取服務(wù)器信息列表 ???? ?* ???? ?* @throws Exception ???? ?*/ ???? public void getServerList() throws Exception { ???????? // 獲取服務(wù)器子節(jié)點信息，并且對父節(jié)點進行監(jiān)聽 ???????? List<String> children = zk.getChildren(parentNode, true); ? ???????? // 先創(chuàng)建一個局部的list來存服務(wù)器信息 ???????? List<String> servers = new ArrayList<String>(); ???????? for (String child : children) { ????????????? // child只是子節(jié)點的節(jié)點名 ????????????? byte[] data = zk.getData(parentNode + "/" + child, false, null); ????????????? servers.add(new String(data)); ???????? } ???????? // 把servers賦值給成員變量serverList，已提供給各業(yè)務(wù)線程使用 ???????? serverList = servers; ???????? ???????? //打印服務(wù)器列表 ???????? System.out.println(serverList); ???? } ? ???? /** ???? ?* 業(yè)務(wù)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 { ???????? // 獲取zk連接 ???????? DistributedClient client = new DistributedClient(); ???????? client.getConnect(); ???????? // 獲取servers的子節(jié)點信息（并監(jiān)聽），從中獲取服務(wù)器信息列表 ???????? client.getServerList(); ? ???????? // 業(yè)務(wù)線程啟動 ???????? client.handleBussiness(); ???? } } |
2、服務(wù)器端實現(xiàn)
package cn.com.toto.zkonlineoroffline; ? import java.util.concurrent.CountDownLatch; ? import org.apache.zookeeper.CreateMode; import org.apache.zookeeper.WatchedEvent; import org.apache.zookeeper.Watcher; import org.apache.zookeeper.ZooKeeper; import org.apache.zookeeper.Watcher.Event.KeeperState; import org.apache.zookeeper.ZooDefs.Ids; import org.apache.zookeeper.data.Stat; ? public class DistributedServer { ???? private static final String CONNECT_STRING = "192.168.106.80:2181,192.168.106.81:2181,192.168.106.82:2181"; ???? private static final int SESSION_TIME_OUT = 2000; ???? private static final String PARENT_NODE = "/servers"; ? ???? private ZooKeeper zk = null; ???? ???? CountDownLatch countDownLatch = new CountDownLatch(1); ? ???? /** ???? ?* 創(chuàng)建到zk的客戶端連接 ???? ?* ???? ?* @throws Exception ???? ?*/ ???? public void getConnect() throws Exception { ???????? zk = new ZooKeeper(CONNECT_STRING, SESSION_TIME_OUT, new Watcher() { ????????????? @Override ????????????? public void process(WatchedEvent event) { ?????????????????? if(event.getState()==KeeperState.SyncConnected){ ?????????????????????? countDownLatch.countDown(); ?????????????????? } ????????????? } ???????? }); ???????? countDownLatch.await(); ???? } ? ???? /** ???? ?* 向zk集群注冊服務(wù)器信息 ???? ?* ???? ?* @param hostname ???? ?* @throws Exception ???? ?*/ ???? public void registerServer(String hostname) throws Exception { ???????? Stat exists = zk.exists(PARENT_NODE, false); ???????? if(exists==null) zk.create(PARENT_NODE, null, Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT); ???????? String path = zk.create(PARENT_NODE + "/server", hostname.getBytes(), Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL); ???????? System.out.println(hostname + "is online.." + path); ???? } ? ???? /** ???? ?* 業(yè)務(wù)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 { ???????? DistributedServer server = new DistributedServer(); ???????? // 獲取zk連接 ???????? server.getConnect(); ? ???????? // 利用zk連接注冊服務(wù)器信息(主機名) ???????? server.registerServer(args[0]); ? ???????? // 啟動業(yè)務(wù)功能 ???????? server.handleBussiness(args[0]); ???? } } |
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