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

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
>

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
> >
>

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
> > >
> >
>