監聽伺服器節點動態上下線案例分析
1．需求
某分散式系統中，主節點可以有多臺，可以動態上下線，任意一臺客戶端都能實時感知到主節點伺服器的上下線。
2．需求分析，如圖所示
3．具體實現
（0）先在叢集上建立/servers節點
[zk: localhost:2181(CONNECTED) 10] create /servers “servers”
Created /servers
（1）伺服器端向Zookeeper註冊程式碼
package com.atguigu.zkcase;
import java.io.IOException;
import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooKeeper;
import org.apache.zookeeper.ZooDefs.Ids;
public class DistributeServer {
private static String connectString = “hadoop102:2181,hadoop103:2181,hadoop104:2181”;
private static int sessionTimeout = 2000;
private ZooKeeper zk = null;
private String parentNode = “/servers”;
// 建立到zk的客戶端連線
public void getConnect() throws IOException{
zk = new ZooKeeper(connectString, sessionTimeout, new Watcher() {
@Override
public void process(WatchedEvent event) {
}
});
}
// 註冊伺服器
public void registServer(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);
}
// 業務功能
public void business(String hostname) throws Exception{
System.out.println(hostname+” is working …”);
Thread.sleep(Long.MAX_VALUE);
}
public static void main(String[] args) throws Exception {
// 1獲取zk連線
DistributeServer server = new DistributeServer();
server.getConnect();
// 2 利用zk連線註冊伺服器資訊
server.registServer(args[0]);
// 3 啟動業務功能
server.business(args[0]);
}
}
（2）客戶端程式碼
package com.atguigu.zkcase;
import java.io.IOException;
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 DistributeClient {
private static String connectString = “hadoop102:2181,hadoop103:2181,hadoop104:2181”;
private static int sessionTimeout = 2000;
private ZooKeeper zk = null;
private String parentNode = “/servers”;
// 建立到zk的客戶端連線
public void getConnect() throws IOException {
zk = new ZooKeeper(connectString, sessionTimeout, new Watcher() {
@Override
public void process(WatchedEvent event) {
// 再次啟動監聽
try {
getServerList();
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
// 獲取伺服器列表資訊
public void getServerList() throws Exception {
// 1獲取伺服器子節點資訊，並且對父節點進行監聽
List<String> children = zk.getChildren(parentNode, true);
// 2儲存伺服器資訊列表
ArrayList<String> servers = new ArrayList<>();
// 3遍歷所有節點，獲取節點中的主機名稱資訊
for (String child : children) {
byte[] data = zk.getData(parentNode + “/” + child, false, null);
servers.add(new String(data));
}
// 4列印伺服器列表資訊
System.out.println(servers);
}
// 業務功能
public void business() throws Exception{
System.out.println(“client is working …”);
Thread.sleep(Long.MAX_VALUE);
}
public static void main(String[] args) throws Exception {
// 1獲取zk連線
DistributeClient client = new DistributeClient();
client.getConnect();
// 2獲取servers的子節點資訊，從中獲取伺服器資訊列表
client.getServerList();
// 3業務程序啟動
client.business();
}
}
瞭解大資料培訓開發技術知識，關注我，有更多精彩內容與您分享！
文章轉載連結：http://www.atguigu.com/jsfx/13029.html