zookeeper Watcher ZK状态 事件类型

 Watcher ZK状态 事件类型

zookeeper有Watch事件，是一次性出发的，当watch 监视的数据发生变化时,通知设置了该watch的client，即Watcher

同样，其Watcher事监听数据发送了某些变化，那就一定会有对应的事件类型和状态类型

事件类型：（znode节点相关）

EventType.NodeCreated

EventType.NodeDateChanged

EventType.NodeChildrenchanged

EventType.NodeDeleted

状态类型：（是跟客户端实例相关的） Flow 与 Leader Watcher 

KeeperState:Disconnected

KeeperState:SyncConnected

KeeperState:AuthFailed

KeeperState:Expired

c1 c2 相当于client 通过建立一个线程watch 事件监听 zookeeper节点的变化 所以C1 C2 相当于 Watcher ，而且client端可以有多个Watcher 一个Watcher监控一个节点，但Watch事件，是一次性出发的，如果一直监控节点的话 要重复的进行watch。

下面我们通过代码来看一下：

/**
 * Zookeeper Wathcher 
 * 本类就是一个Watcher类（实现了org.apache.zookeeper.Watcher类）
 */
public class ZooKeeperWatcher implements Watcher {

	/** 定义原子变量 */
	AtomicInteger seq = new AtomicInteger();
	/** 定义session失效时间 */
	private static final int SESSION_TIMEOUT = 10000;
	/** zookeeper服务器地址 */
	private static final String CONNECTION_ADDR = "192.168.80.88:2181";
	/** zk父路径设置 */
	private static final String PARENT_PATH = "/testWatch";
	/** zk子路径设置 */
	private static final String CHILDREN_PATH = "/testWatch/children";
	/** 进入标识 */
	private static final String LOG_PREFIX_OF_MAIN = "【Main】";
	/** zk变量 */
	private ZooKeeper zk = null;
	/** 信号量设置，用于等待zookeeper连接建立之后 通知阻塞程序继续向下执行 */
	private CountDownLatch connectedSemaphore = new CountDownLatch(1);

	/**
	 * 创建ZK连接
	 * @param connectAddr ZK服务器地址列表
	 * @param sessionTimeout Session超时时间
	 */
	public void createConnection(String connectAddr, int sessionTimeout) {
		this.releaseConnection();
		try {
			zk = new ZooKeeper(connectAddr, sessionTimeout, this);
			System.out.println(LOG_PREFIX_OF_MAIN + "开始连接ZK服务器");
			connectedSemaphore.await();
		} catch (Exception e) {
			e.printStackTrace();
		}
	}

	/**
	 * 关闭ZK连接
	 */
	public void releaseConnection() {
		if (this.zk != null) {
			try {
				this.zk.close();
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
		}
	}

	/**
	 * 创建节点
	 * @param path 节点路径
	 * @param data 数据内容
	 * @return 
	 */
	public boolean createPath(String path, String data) {
		try {
			//设置监控(由于zookeeper的监控都是一次性的所以 每次必须设置监控)
			this.zk.exists(path, true);
			System.out.println(LOG_PREFIX_OF_MAIN + "节点创建成功, Path: " + 
							   this.zk.create(	/**路径*/ 
									   			path, 
									   			/**数据*/
									   			data.getBytes(), 
									   			/**所有可见*/
								   				Ids.OPEN_ACL_UNSAFE, 
								   				/**永久存储*/
								   				CreateMode.PERSISTENT ) + 	
							   ", content: " + data);
		} catch (Exception e) {
			e.printStackTrace();
			return false;
		}
		return true;
	}

	/**
	 * 读取指定节点数据内容
	 * @param path 节点路径
	 * @return
	 */
	public String readData(String path, boolean needWatch) {
		try {
			return new String(this.zk.getData(path, needWatch, null));
		} catch (Exception e) {
			e.printStackTrace();
			return "";
		}
	}

	/**
	 * 更新指定节点数据内容
	 * @param path 节点路径
	 * @param data 数据内容
	 * @return
	 */
	public boolean writeData(String path, String data) {
		try {
			System.out.println(LOG_PREFIX_OF_MAIN + "更新数据成功，path：" + path + ", stat: " +
								this.zk.setData(path, data.getBytes(), -1));
		} catch (Exception e) {
			e.printStackTrace();
		}
		return false;
	}

	/**
	 * 删除指定节点
	 * 
	 * @param path
	 *            节点path
	 */
	public void deleteNode(String path) {
		try {
			this.zk.delete(path, -1);
			System.out.println(LOG_PREFIX_OF_MAIN + "删除节点成功，path：" + path);
		} catch (Exception e) {
			e.printStackTrace();
		}
	}

	/**
	 * 判断指定节点是否存在
	 * @param path 节点路径
	 */
	public Stat exists(String path, boolean needWatch) {
		try {
			return this.zk.exists(path, needWatch);
		} catch (Exception e) {
			e.printStackTrace();
			return null;
		}
	}

	/**
	 * 获取子节点
	 * @param path 节点路径
	 */
	private List getChildren(String path, boolean needWatch) {
		try {
			return this.zk.getChildren(path, needWatch);
		} catch (Exception e) {
			e.printStackTrace();
			return null;
		}
	}

	/**
	 * 删除所有节点
	 */
	public void deleteAllTestPath() {
		if(this.exists(CHILDREN_PATH, false) != null){
			this.deleteNode(CHILDREN_PATH);
		}
		if(this.exists(PARENT_PATH, false) != null){
			this.deleteNode(PARENT_PATH);
		}		
	}
	
	/**
	 * 收到来自Server的Watcher通知后的处理。
	 */
	@Override
	public void process(WatchedEvent event) {
		
		System.out.println("进入 process 。。。。。event = " + event);
		
		try {
			Thread.sleep(200);
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
		
		if (event == null) {
			return;
		}
		
		// 连接状态
		KeeperState keeperState = event.getState();
		// 事件类型
		EventType eventType = event.getType();
		// 受影响的path
		String path = event.getPath();
		
		String logPrefix = "【Watcher-" + this.seq.incrementAndGet() + "】";

		System.out.println(logPrefix + "收到Watcher通知");
		System.out.println(logPrefix + "连接状态:\t" + keeperState.toString());
		System.out.println(logPrefix + "事件类型:\t" + eventType.toString());

		if (KeeperState.SyncConnected == keeperState) {
			// 成功连接上ZK服务器
			if (EventType.None == eventType) {
				System.out.println(logPrefix + "成功连接上ZK服务器");
				connectedSemaphore.countDown();
			} 
			//创建节点
			else if (EventType.NodeCreated == eventType) {
				System.out.println(logPrefix + "节点创建");
				try {
					Thread.sleep(100);
				} catch (InterruptedException e) {
					e.printStackTrace();
				}
				this.exists(path, true);
			} 
			//更新节点
			else if (EventType.NodeDataChanged == eventType) {
				System.out.println(logPrefix + "节点数据更新");
				System.out.println("我看看走不走这里........");
				try {
					Thread.sleep(100);
				} catch (InterruptedException e) {
					e.printStackTrace();
				}
				System.out.println(logPrefix + "数据内容: " + this.readData(PARENT_PATH, true));
			} 
			//更新子节点
			else if (EventType.NodeChildrenChanged == eventType) {
				System.out.println(logPrefix + "子节点变更");
				try {
					Thread.sleep(3000);
				} catch (InterruptedException e) {
					e.printStackTrace();
				}
				System.out.println(logPrefix + "子节点列表：" + this.getChildren(PARENT_PATH, true));
			} 
			//删除节点
			else if (EventType.NodeDeleted == eventType) {
				System.out.println(logPrefix + "节点 " + path + " 被删除");
			}
			else ;
		} 
		else if (KeeperState.Disconnected == keeperState) {
			System.out.println(logPrefix + "与ZK服务器断开连接");
		} 
		else if (KeeperState.AuthFailed == keeperState) {
			System.out.println(logPrefix + "权限检查失败");
		} 
		else if (KeeperState.Expired == keeperState) {
			System.out.println(logPrefix + "会话失效");
		}
		else ;

		System.out.println("--------------------------------------------");

	}

	/**
	 * 方法名称：测试zookeeper监控

	 * 概要说明：主要测试watch功能

	 * @param args
	 * @throws Exception
	 */
	public static void main(String[] args) throws Exception {

		//建立watcher
		ZooKeeperWatcher zkWatch = new ZooKeeperWatcher();
		//创建连接
		zkWatch.createConnection(CONNECTION_ADDR, SESSION_TIMEOUT);
		//System.out.println(zkWatch.zk.toString());
		
		Thread.sleep(1000);
		
		// 清理节点
		zkWatch.deleteAllTestPath();
		
		if (zkWatch.createPath(PARENT_PATH, System.currentTimeMillis() + "")) {
			
			Thread.sleep(1000);
			
			
			// 读取数据
			System.out.println("---------------------- read parent ----------------------------");
			//zkWatch.readData(PARENT_PATH, true);
			
			// 读取子节点
			System.out.println("---------------------- read children path ----------------------------");
			zkWatch.getChildren(PARENT_PATH, true);

			// 更新数据
			zkWatch.writeData(PARENT_PATH, System.currentTimeMillis() + "");
			
			Thread.sleep(1000);
			
			// 创建子节点
			zkWatch.createPath(CHILDREN_PATH, System.currentTimeMillis() + "");
			
			Thread.sleep(1000);
			
			zkWatch.writeData(CHILDREN_PATH, System.currentTimeMillis() + "");
		}
		
		Thread.sleep(50000);
		// 清理节点
		zkWatch.deleteAllTestPath();
		Thread.sleep(1000);
		zkWatch.releaseConnection();
	}

}

 下节链接地址http://blog.csdn.net/lm324114/article/details/78388638