zookeeper应用 - leader选举 锁

package leader;
import java.util.List;
import java.util.concurrent.TimeUnit;
import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.KeeperException;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.Watcher.Event.EventType;
import org.apache.zookeeper.ZooDefs.Ids;
import org.apache.zookeeper.ZooKeeper;
/**
 * 模拟leader选举
 * 
 * 1、zookeeper服务器上有一个/leader节点
 * 2、在/leader节点下创建短暂顺序节点/leader/lock-xxxxxxx
 * 3、获取/leader的所有子节点并注册监听
 * 4、拿自己的顺序号跟其他子节点的顺序号比较，如果自己的是最小的则获得leader
 * 5、监听到/leader子节点发生变化则执行步骤3、 4尝试获取leader
 *
 */
public class Client {
	
	public static final String HOSTS = "hadoop1:2181";
	public static final String LEADER_PATH = "/leader";
	
	private String path = null;
	
	public void run() throws Exception {
		ZooKeeper zk = ZKUtils.open(HOSTS);
		path = zk.create(LEADER_PATH + "/lock-", null, Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL);
		
		getLeader(zk);
		
		TimeUnit.DAYS.sleep(1);
	}
	private void getLeader(final ZooKeeper zk)
			throws KeeperException, InterruptedException {
		//获取/leader下的所有子节点
		//注册/leader子节点观察
		List<String> children = zk.getChildren(LEADER_PATH, new Watcher() {
			@Override
			public void process(WatchedEvent event) {
				//如果/leader子节点发生变化，则再进行一次getLeader
				if(event.getType().equals(EventType.NodeChildrenChanged)) {
					try {
						getLeader(zk);
					} catch (KeeperException e) {
						e.printStackTrace();
					} catch (InterruptedException e) {
						e.printStackTrace();
					}
				}
			}
		});
		
		//拿自己的顺序号跟/leader所有子节点的顺序号比较，如果是最小的则拿到leader
		long seq = getSeq(path);
		boolean isMin = true;
		for (String child : children) {
			long childSeq = getSeq(child);
			if(childSeq < seq) {
				isMin = false;
				break;
			}
		}
		if(isMin) {
			System.out.printf("我拿到锁了, path: %s, thread: %s", path, Thread.currentThread().getName() );
		}
	}
	
	public long getSeq(String path) {
		return Long.parseLong(path.split("-")[1]);
	}
}

package leader;
public class Test {
	//多次执行这个类，模拟多个客户端竞选leader
	public static void main(String[] args) throws Exception {
		new Client().run();
	}
}