9.使用GetData,Children实现对ZNode的监控

一、 zookeeper中的watcher

1. exists ：监控的是【znode】的CUD 的操作

 

2. getdata 的时候注册的watcher【U,D 监控】update delete

exists 可以获取到当前的节点，但是无法获取到内容。

getdata 可以获取到最新的内容。

异常： 如果znode不存，是无法监控getdata

官方文档： A KeeperException with error code KeeperException.NoNode will be thrown if no node with the given path exists.

　　　　

　　　　同样的实现接口IWatcher

　　　　

    public class DataWatcher: IWatcher
    {
        private ZooKeeper _zookeeper = null;
        Action<WatchedEvent, string> _action = null;

        public DataWatcher(ZooKeeper zookeeper, Action<WatchedEvent, string> action)
        {
            _zookeeper = zookeeper;
            _action = action;
        }

        public void Process(WatchedEvent @event)
        {
            try
            {
                //Console.WriteLine("path={0},state={1},type={2}", @event.Path, @event.State, @event.Type);
                //通过getdata获取内容
                var content = Encoding.UTF8.GetString(_zookeeper.GetData(@event.Path, this, null));
                if (_action != null)
                {
                    _action(@event, content);
                }
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message);
            }
        }
    }

　　使用：

　　

            Console.WriteLine("欢迎来到zookeeper.net 9 ");
            try
            {
                var bytes = zookeeper.GetData("/google", new DataWatcher(zookeeper, (e, data) =>
                 {
                     //data 是返回的内容
                     Console.WriteLine("path={0},state={1},type={2},data={3}", e.Path, e.State, e.Type, data);
                 }), null);
            }
            catch (KeeperException ex)
            {
                throw new Exception(ex.Message);
            }

　　3. getchildren 的时候注册的watcher

　　　　子节点的add,remove 都是能够监控的到状态。【Update是监控不到的，需要使用exists】

 

   public class ChildrenWatcher : IWatcher
    {
        private ZooKeeper _zookeeper = null;
        Action<WatchedEvent, IEnumerable<string>> _action = null;

        public ChildrenWatcher(ZooKeeper zookeeper, Action<WatchedEvent, IEnumerable<string>> action)
        {
            _zookeeper = zookeeper;
            _action = action;
        }

        public void Process(WatchedEvent @event)
        {
            try
            {
                //通过getdata获取内容
                var list = _zookeeper.GetChildren(@event.Path, this, null);
                if (_action != null)
                {
                    _action(@event, list);
                }
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message);
            }
        }

    }

try
            {
              var list_t = zookeeper.GetChildren("/google", new ChildrenWatcher(zookeeper, (e, data) =>
                {
                    Console.WriteLine("path={0},state={1},type={2},data={3}", e.Path, e.State, e.Type, string.Join(",", data));
                }), null);

            }
            catch (KeeperException ex)
            {
                throw new Exception(ex.Message);
            }

执行创建，删除后的效果

　　

监听结果

　　

 

应用场景：

　　【智能感知上下线】 服务注（provider） 和发现（client）