zookeeper应用

服务器端：监听zk上父节点的子节点变化

1. package monitor;
   import java.util.List;
   import java.util.concurrent.CountDownLatch;
   import java.util.concurrent.TimeUnit;
   import org.apache.zookeeper.CreateMode;
   import org.apache.zookeeper.WatchedEvent;
   import org.apache.zookeeper.Watcher;
   import org.apache.zookeeper.Watcher.Event.KeeperState;
   import org.apache.zookeeper.ZooDefs;
   import org.apache.zookeeper.ZooKeeper;
   /**
    * 监听客户端的上下线
    * @author lisg
    *
    */
   public class ServerMonitor {
   	public static final String HOSTS = "vm1";
   	private ZooKeeper zk = null;
   	
   	public static final String PARENT_PATH = "/monitor";
   	
   	private static int client_count = 0;
   	public ServerMonitor() {
   		final CountDownLatch cdl = new CountDownLatch(1);
   		try {
   			zk = new ZooKeeper(HOSTS, 5000, new Watcher() {
   				@Override
   				public void process(WatchedEvent event) {
   					if(KeeperState.SyncConnected.equals(event.getState())) {
   						cdl.countDown();
   					}
   				}
   			});
   			
   			cdl.await();
   			
   			//创建父节点
   			if(zk.exists(PARENT_PATH, false) == null) {
   				zk.create(PARENT_PATH, 
   						"".getBytes(), 
   						ZooDefs.Ids.OPEN_ACL_UNSAFE, 
   						CreateMode.PERSISTENT);
   			}
   		} catch (Exception e) {
   			e.printStackTrace();
   		}
   	}
   	
   	public void run() {
   		try {
   			zk.getChildren(PARENT_PATH, new ClientChangeWatcher());
   		} catch (Exception e) {
   			e.printStackTrace();
   		}
   	}
   	
   	class ClientChangeWatcher implements Watcher {
   		@Override
   		public void process(WatchedEvent event) {
   			try {
   				if(Event.EventType.NodeChildrenChanged.equals(event.getType())) {
   					//获取子节点，同时注册监听
   					final List<String> children = zk.getChildren(PARENT_PATH, this);
   					if(client_count > children.size()) {
   						System.out.println("有客户端下线");
   					} else {
   						System.out.println("有客户端上线");
   					}
   					client_count = children.size();
   				}
   			} catch (Exception e) {
   				e.printStackTrace();
   			}
   		}
   	}
   	
   	public static void main(String[] args) {
   		new ServerMonitor().run();
   		
   		try {
   			TimeUnit.DAYS.sleep(1);
   		} catch (InterruptedException e) {
   			e.printStackTrace();
   		}
   	}
   }
   

   　　

 

客户端：上线的时候在父节点上创建短暂的子节点

 

package monitor;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.TimeUnit;
import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.Watcher.Event.KeeperState;
import org.apache.zookeeper.ZooDefs.Ids;
import org.apache.zookeeper.ZooKeeper;
/**
 * 客户端
 * 上线的时候在zk上创建一个短暂的子节点
 * @author lisg
 *
 */
public class Client {
	
	public static final String CLIENT_PATH_PREFIX = "cli-";
	public static void main(String[] args) {
		final CountDownLatch cdl = new CountDownLatch(1);
		try {
			ZooKeeper zk = new ZooKeeper(ServerMonitor.HOSTS, 5000, new Watcher() {
				@Override
				public void process(WatchedEvent event) {
					if(KeeperState.SyncConnected.equals(event.getState())) {
						cdl.countDown();
					}
				}
			});
			
			cdl.await();
			
			//创建父节点
			zk.create(ServerMonitor.PARENT_PATH + "/" + CLIENT_PATH_PREFIX, 
					"".getBytes(), 
					Ids.OPEN_ACL_UNSAFE, 
					CreateMode.EPHEMERAL_SEQUENTIAL);
			
			TimeUnit.SECONDS.sleep(5);
			zk.close();
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
}

　　

来自为知笔记(Wiz)

附件列表