Read the rest of that web page. Read this exchange as well: http://zookeeper-user.578899.n2.nabble.com/Persistent-watch-stream-td5734685.html
<http://zookeeper-user.578899.n2.nabble.com/Persistent-watch-stream-td5734685.html>Do a google search and summarize what you find in your next question. 2011/6/21 lei liu <[email protected]> > Hi Ted, thank you for your reply. > > Can you tell me why I need to reset the watch? I think that is confusing. > > Thanks, > > LiuLei > > > 2011/6/21 Ted Dunning <[email protected]> > > > Note the part about "and clear the watch" > > > > > > > http://zookeeper.apache.org/doc/r3.1.2/zookeeperProgrammers.html#sc_zkDataMode_watches > > > > your process method must reset the watch. This behavior is intentional > and > > quite important for ZK to work correctly. > > > > 2011/6/21 lei liu <[email protected]> > > > > > I use Zookeeper 3.3.3 version. > > > > > > I create "test" znode, and I add many children for the znode. I want to > > > listen EventType.NodeChildrenChanged event, when there is > > > EventType.NodeChildrenChanged event, I print the event information, > > example > > > below code: > > > > > > public class DisplayGroup implements Watcher { > > > > > > private static final int SESSION_TIMEOUT = 5000; > > > > > > protected ZooKeeper zk; > > > > > > public void connect(String hosts) throws IOException, > > > InterruptedException { > > > zk = new ZooKeeper(hosts, SESSION_TIMEOUT, this); > > > > > > } > > > > > > @Override > > > public void process(WatchedEvent event) { > > > > > > System.out.println(this.getClass().getName() + ": " + event); > > > } > > > > > > public void close() throws InterruptedException { > > > zk.close(); > > > } > > > > > > public void list(String groupName) throws KeeperException, > > > InterruptedException { > > > String path = "/" + groupName; > > > try { > > > > > > List<String> children = zk.getChildren(path, true); > > > if (children.isEmpty()) { > > > System.out.printf("No members in group %s\n", > groupName); > > > > > > } > > > for (String child : children) { > > > System.out.println(child); > > > } > > > } catch (KeeperException.NoNodeException e) { > > > System.out.printf("Group %s does not exist\n", groupName); > > > > > > } > > > } > > > > > > public static void main(String[] args) throws Exception { > > > DisplayGroup listGroup = new DisplayGroup(); > > > String connectString = "localhost:2181"; > > > listGroup.connect(connectString); > > > listGroup.list("test"); > > > Thread.sleep(Long.MAX_VALUE); > > > } > > > > > > } > > > > > > > > > I add many children to the "test" znode, but the process() method of > > > DisplayGroup calss only is called one time, the output information is： > > > 1308621717188 > > > 1308621719250 > > > examples.DisplayGroup: WatchedEvent state:SyncConnected > > > type:NodeChildrenChanged path:/test > > > > > > > > > > > > I want to know why the process() method of DisplayGroup calss is not > > > called > > > many times when I add many children to the "test" znode? > > > > > > > > > Thanks, > > > > > > > > > LiuLei > > > > > >
