How to recover previous watcher & event after "session expired"

[李赫元 <li...@gmail.com>]

Hi, All

I'm dealing with the case of "session expired" event. Please help me
with the following question.

1. After receive "session expired" event, how to recover the watch
that are setting before expired gracefully?


2.Currently, I record the watch setting and call the api to set it
again after I got "expired event". It will callback for event after
connection was success again. But what about the event happend between
I success reinit the session to zk server. Currently, it got lost. Is
there any way that I can got these events ?


3.I try to use reconnect, in zookeeper_init, but does't work. My guess
is reconnect is only work for connection that are in state connect
(Not valid after session timeout), is it right?


Thanks for your help !

Re: How to recover previous watcher & event after "session expired"

[李赫元 <li...@gmail.com>]

Thanks for your help all the time.

Best Regargs,
Heyuan Li


2012/5/20 Martin Kou <bi...@gmail.com>:
> Correct. And even simple connection losses can cause watches to become
> unreliable as well:
>
> http://zookeeper.apache.org/doc/trunk/releasenotes.html#Watch+Management
> "One caveat to the watch management: it is possible to miss an event for
> the creation and deletion of a znode if watching for creation and both the
> create and delete happens while the client is disconnected from ZooKeeper."
>
> Best Regards,
> Martin Kou
>
> On Fri, May 18, 2012 at 8:33 PM, 李赫元 <li...@gmail.com> wrote:
>
>> Thanks for your help.
>> That means we can't totally rely on watchs because it may loss event if
>> session expired, right?
>>
>> 在 2012年5月19日星期六，Camille Fournier <ca...@apache.org> 写道：
>> > I'm not sure what you mean in question #1. A session expired event
>> > generally causes the client to become completely invalid, you could
>> > wrap the client in your own logic to record what you were watching,
>> > but I don't think you can get that out of the client after it's
>> > expired.
>> >
>> > 2. You won't be able to see events that happened when the session was
>> > expired. The server has closed your connection and won't know to send
>> > you events unless you have a valid session with a valid watch.
>> >
>> > 3. Reconnect won't work on expired sessions, you need to create an
>> > entirely new session. Reconnect works when you get disconnected but
>> > not expired.
>> >
>> > Hope that helps
>> > On Fri, May 18, 2012 at 12:18 PM, 李赫元 <li...@gmail.com> wrote:
>> >> Hi, All
>> >>
>> >> I'm dealing with the case of "session expired" event. Please help me
>> >> with the following question.
>> >>
>> >> 1. After receive "session expired" event, how to recover the watch
>> >> that are setting before expired gracefully?
>> >>
>> >>
>> >> 2.Currently, I record the watch setting and call the api to set it
>> >> again after I got "expired event". It will callback for event after
>> >> connection was success again. But what about the event happend between
>> >> I success reinit the session to zk server. Currently, it got lost. Is
>> >> there any way that I can got these events ?
>> >>
>> >>
>> >> 3.I try to use reconnect, in zookeeper_init, but does't work. My guess
>> >> is reconnect is only work for connection that are in state connect
>> >> (Not valid after session timeout), is it right?
>> >>
>> >>
>> >> Thanks for your help !
>> >
>>

Re: How to recover previous watcher & event after "session expired"

[Martin Kou <bi...@gmail.com>]

Correct. And even simple connection losses can cause watches to become
unreliable as well:

http://zookeeper.apache.org/doc/trunk/releasenotes.html#Watch+Management
"One caveat to the watch management: it is possible to miss an event for
the creation and deletion of a znode if watching for creation and both the
create and delete happens while the client is disconnected from ZooKeeper."

Best Regards,
Martin Kou

On Fri, May 18, 2012 at 8:33 PM, 李赫元 <li...@gmail.com> wrote:

> Thanks for your help.
> That means we can't totally rely on watchs because it may loss event if
> session expired, right?
>
> 在 2012年5月19日星期六，Camille Fournier <ca...@apache.org> 写道：
> > I'm not sure what you mean in question #1. A session expired event
> > generally causes the client to become completely invalid, you could
> > wrap the client in your own logic to record what you were watching,
> > but I don't think you can get that out of the client after it's
> > expired.
> >
> > 2. You won't be able to see events that happened when the session was
> > expired. The server has closed your connection and won't know to send
> > you events unless you have a valid session with a valid watch.
> >
> > 3. Reconnect won't work on expired sessions, you need to create an
> > entirely new session. Reconnect works when you get disconnected but
> > not expired.
> >
> > Hope that helps
> > On Fri, May 18, 2012 at 12:18 PM, 李赫元 <li...@gmail.com> wrote:
> >> Hi, All
> >>
> >> I'm dealing with the case of "session expired" event. Please help me
> >> with the following question.
> >>
> >> 1. After receive "session expired" event, how to recover the watch
> >> that are setting before expired gracefully?
> >>
> >>
> >> 2.Currently, I record the watch setting and call the api to set it
> >> again after I got "expired event". It will callback for event after
> >> connection was success again. But what about the event happend between
> >> I success reinit the session to zk server. Currently, it got lost. Is
> >> there any way that I can got these events ?
> >>
> >>
> >> 3.I try to use reconnect, in zookeeper_init, but does't work. My guess
> >> is reconnect is only work for connection that are in state connect
> >> (Not valid after session timeout), is it right?
> >>
> >>
> >> Thanks for your help !
> >
>

Re: How to recover previous watcher & event after "session expired"

[李赫元 <li...@gmail.com>]

Thanks for your help.
That means we can't totally rely on watchs because it may loss event if
session expired, right?

在 2012年5月19日星期六，Camille Fournier <ca...@apache.org> 写道：
> I'm not sure what you mean in question #1. A session expired event
> generally causes the client to become completely invalid, you could
> wrap the client in your own logic to record what you were watching,
> but I don't think you can get that out of the client after it's
> expired.
>
> 2. You won't be able to see events that happened when the session was
> expired. The server has closed your connection and won't know to send
> you events unless you have a valid session with a valid watch.
>
> 3. Reconnect won't work on expired sessions, you need to create an
> entirely new session. Reconnect works when you get disconnected but
> not expired.
>
> Hope that helps
> On Fri, May 18, 2012 at 12:18 PM, 李赫元 <li...@gmail.com> wrote:
>> Hi, All
>>
>> I'm dealing with the case of "session expired" event. Please help me
>> with the following question.
>>
>> 1. After receive "session expired" event, how to recover the watch
>> that are setting before expired gracefully?
>>
>>
>> 2.Currently, I record the watch setting and call the api to set it
>> again after I got "expired event". It will callback for event after
>> connection was success again. But what about the event happend between
>> I success reinit the session to zk server. Currently, it got lost. Is
>> there any way that I can got these events ?
>>
>>
>> 3.I try to use reconnect, in zookeeper_init, but does't work. My guess
>> is reconnect is only work for connection that are in state connect
>> (Not valid after session timeout), is it right?
>>
>>
>> Thanks for your help !
>

Re: How to recover previous watcher & event after "session expired"

[Camille Fournier <ca...@apache.org>]

I'm not sure what you mean in question #1. A session expired event
generally causes the client to become completely invalid, you could
wrap the client in your own logic to record what you were watching,
but I don't think you can get that out of the client after it's
expired.

2. You won't be able to see events that happened when the session was
expired. The server has closed your connection and won't know to send
you events unless you have a valid session with a valid watch.

3. Reconnect won't work on expired sessions, you need to create an
entirely new session. Reconnect works when you get disconnected but
not expired.

Hope that helps
On Fri, May 18, 2012 at 12:18 PM, 李赫元 <li...@gmail.com> wrote:
> Hi, All
>
> I'm dealing with the case of "session expired" event. Please help me
> with the following question.
>
> 1. After receive "session expired" event, how to recover the watch
> that are setting before expired gracefully?
>
>
> 2.Currently, I record the watch setting and call the api to set it
> again after I got "expired event". It will callback for event after
> connection was success again. But what about the event happend between
> I success reinit the session to zk server. Currently, it got lost. Is
> there any way that I can got these events ?
>
>
> 3.I try to use reconnect, in zookeeper_init, but does't work. My guess
> is reconnect is only work for connection that are in state connect
> (Not valid after session timeout), is it right?
>
>
> Thanks for your help !