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Re: [Zookeeper-user] [Bug?] Notification not guaranteed
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From: Patrick H. <ph...@gm...> - 2008-04-25 17:06:45
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On Fri, Apr 25, 2008 at 8:48 AM, Benjamin Reed <br...@ya...> wrote:
> Naming and the semantics it implies can be an endless argument. Unless we
> call
> it a one time trigger I think people will think of SQL triggers which are
> not
> one time. (I'm not saying that watch is any better.
Agree - otw I would have suggested changing it. ;-) Just wanted to point
out that this was an issue in my internalizing the feature.
>
> I agree about the java doc clarifications. I've been working on it since
> Ted
> brought it up, but I've been side tracked by the session loss bug. I'm
> hoping
> to finish up today. I'll make sure the javadoc emphasizes the way watches
> work.
I should have entered a bug really, my bad.
>
>
> ben
>
> On Friday 25 April 2008 00:14:11 Patrick Hunt wrote:
> > Benjamin Reed wrote:
> > > This is really a key point for new users to understand, so any pointers
> > > on how we can clarify that page would be very helpful!
> >
> > Part of the issue may be the naming itself. For whatever reason I
> > associate "watch" with something long lived - not a "one time
> > notification" which I would associate more naturally with "trigger".
> >
> > I jumped in right way and started using the java client/server. The java
> > client javadoc in particular is not clear about watches being "one time
> > notifications". Would def help to fix the javadoc on this point.
> >
> > Patrick
> >
> > > ----- Original Message ----
> > > From: Stefan Groschupf <sg...@10...>
> > > To: zoo...@li...
> > > Sent: Thursday, April 24, 2008 10:19:16 PM
> > > Subject: [Zookeeper-user] [Bug?] Notification not guaranteed
> > >
> > > Hi there,
> > > as far I understand notification is guaranteed for e.g. child creation.
> > > However I have a test that shows that randomly I do not get all
> > > notification I do expect.
> > > I basically create 10 child in /folder but only get 8 or 9
> > > notifications back.
> > > However in case I add a Thread.sleep(50); between my child znode
> > > creation I always get 10 notifications.
> > >
> > > Is that a bug or an optimization, e.g. getting one notification for
> > > two new sub znode creations?
> > > Thanks for any hints.
> > > Stefan
> > >
> > > My code looks like this:
> > >
> > > TestMethod:
> > >
> > > public void testNotifications() throws Exception {
> > > KattaConfiguration conf = new KattaConfiguration();
> > > Server server = new Server(conf);
> > > ZKClient client = new ZKClient(conf);
> > > MyListener listener = new MyListener();
> > > String katta = "/katta";
> > > if (client.exists(katta)) {
> > > client.deleteRecursiv(katta);
> > > }
> > > client.create(katta);
> > > client.subscribeChildChanges(katta, listener);
> > > for (int i = 0; i < 10; i++) {
> > > client.create(katta + "/" + i);
> > > // Thread.sleep(50);
> > > }
> > > Thread.sleep(1000);
> > > assertEquals(10, listener._counter);
> > > server.shutdown();
> > > }
> > >
> > > Watcher process Method:
> > >
> > > public void process(WatcherEvent event) {
> > > synchronized (_mutex) {
> > > String path = event.getPath();
> > > if (event.getType() ==
> > > Watcher.Event.EventNodeChildrenChanged) {
> > > HashSet<IZKEventListener> listeners =
> > > _childListener.get(path);
> > > if (listeners != null) {
> > > for (IZKEventListener listener : listeners) {
> > > listener.process(event);
> > > }
> > > // re subscribe to event.
> > > try {
> > > _zk.getChildren(event.getPath(), true);
> > > } catch (Exception e) {
> > > for (IZKEventListener listener : listeners) {
> > > removeListener(path, listener);
> > > }
> > > Logger.warn("unable to re subscribe to child
> > > change notification", e);
> > > }
> > > }
> > > }
> > > }
> > > }
> > >
> > >
> > >
> > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > > 101tec Inc.
> > > Menlo Park, California, USA
> > > http://www.101tec.com
> > >
> > >
> > >
> > >
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