zookeeper监听服务器节点动态上下线
需求：某分布式系统中，主节点有多台，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
实现思路：
- 服务器上线后，就在zookeeper集群上注册（要在zookeeper集群上创建一个临时node，以便服务器下线时就可以在zookeeper集群上删掉该临时node）。
- 客户端上线后，使用getChildren() 获取当前在线服务器列表，并注册监听。
- 当服务器下线后，zookeeper集群上该临时节点就会删掉，服务器下线事件通知客户端。
- 客户端在process()中，再重新获取在线服务器列表，并重新注册监听。
package com.allen.zookeeper01;
import org.apache.zookeeper.*;
import java.io.IOException;
public class DistributeServer {
private String connectString = "hadoop02:2181,hadoop03:2181,hadoop04:2181";
private int sessionTimeout = 2000;
private ZooKeeper zk;
public static void main(String[] args) {
DistributeServer server = new DistributeServer();
// 连接zookeeper集群连接
try {
server.getConnect();
} catch (IOException e) {
e.printStackTrace();
}// 注册节点
try {
server.register(args[0]);
} catch (KeeperException e) {
e.printStackTrace();
} catch (InterruptedException e) {
e.printStackTrace();
}// 业务逻辑处理
try {
server.business();
} catch (InterruptedException e) {
e.printStackTrace();
}}private void business() throws InterruptedException {
Thread.sleep(Long.MAX_VALUE);
}private void register(String hostname) throws KeeperException, InterruptedException {
zk.create("/servers/server", hostname.getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL);
System.out.println(hostname + " is online. ");
}private void getConnect() throws IOException {
zk = new ZooKeeper(connectString, sessionTimeout, new Watcher() {
public void process(WatchedEvent watchedEvent) {}
});
}
}客户端代码：
package com.allen.zookeeper01;
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 DistributedClient {
private String connectString = "hadoop02:2181,hadoop03:2181,hadoop04:2181";
private int sessionTimeout = 2000;
private ZooKeeper zk;
public static void main(String[] args) {
DistributedClient client = new DistributedClient();
// 获取zookeeper集群连接
try {
client.getConnect();
} catch (IOException e) {
e.printStackTrace();
}// 注册监听
try {
client.getChildren();
} catch (KeeperException e) {
e.printStackTrace();
} catch (InterruptedException e) {
e.printStackTrace();
}// 业务逻辑处理
try {
client.business();
} catch (InterruptedException e) {
e.printStackTrace();
}}private void business() throws InterruptedException {
Thread.sleep(Long.MAX_VALUE);
}private void getChildren() throws KeeperException, InterruptedException {
List children = zk.getChildren("/servers", true);
ArrayList hosts = new ArrayList();
for (String child : children) {
byte[] data = https://www.it610.com/article/zk.getData("/servers/" + child, false, null);
hosts.add(new String(data));
}// 将所有在线的服务器打印
System.out.println(hosts);
}private void getConnect() throws IOException {
zk = new ZooKeeper(connectString, sessionTimeout, new Watcher() {
public void process(WatchedEvent watchedEvent) {
try {
getChildren();
} catch (KeeperException e) {
e.printStackTrace();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
});
}
}【zookeeper监听服务器节点动态上下线】效果如图：
文章图片
- 无服务器上线
- hadoop02上线
- hadoop03上线
- hadoop03下线
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