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Zookeeper >> mail # user >> lost ZK events across datacenters


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Re: lost ZK events across datacenters
actually, i think the transaction log could help a lot, and that will
always be there. two scenarios i can think of are:
1) the change happened before the watch was set
2) the change never got there
you could get an answer to both of those questions by looking at the
transaction log.

ben

On Fri, Jun 3, 2011 at 9:59 AM, Jun Rao <[EMAIL PROTECTED]> wrote:
> I don't expect that we can discover the problem right now. However, what are
> the things that I can do to collect enough tracing should the problem occur
> again in the future (e.g., is INFO level logging enough)?
>
> Thanks,
>
> Jun
>
> On Fri, Jun 3, 2011 at 9:56 AM, Jun Rao <[EMAIL PROTECTED]> wrote:
>
>> The log doesn't have any state changing entries around the time the watcher
>> is triggered, in all clients.
>>
>> Jun
>>
>>
>> On Fri, Jun 3, 2011 at 9:32 AM, Fournier, Camille F. [Tech] <
>> [EMAIL PROTECTED]> wrote:
>>
>>> Any state changes for the problem client between setting the watch and
>>> when you expected it to get called? Do you have logs for that client vs the
>>> others that show anything?
>>>
>>> -----Original Message-----
>>> From: Jun Rao [mailto:[EMAIL PROTECTED]]
>>> Sent: Friday, June 03, 2011 4:40 AM
>>> To: [EMAIL PROTECTED]
>>> Subject: Re: lost ZK events across datacenters
>>>
>>> Ben,
>>>
>>> Some details below.
>>>
>>> The call that sets the watcher simple calls getChildren with watcher flag
>>> set to true. The triggering change is that one of the child nodes (which
>>> is
>>> ephemeral) is deleted because the creating client is gone.
>>>
>>> Thanks,
>>>
>>> Jun
>>>
>>> On Thu, Jun 2, 2011 at 10:49 AM, Benjamin Reed <[EMAIL PROTECTED]> wrote:
>>>
>>> > can you tell us a bit more about the scenario? what was the call the
>>> > set the watch event? and what were the changes that caused the event?
>>> >
>>> > thanx
>>> > ben
>>> >
>>> > On Wed, Jun 1, 2011 at 3:14 PM, Jun Rao <[EMAIL PROTECTED]> wrote:
>>> > > All my clients were on different machines. 2 of them got the watcher
>>> > fired
>>> > > about the same time. The third one never got the watcher triggered.
>>> > >
>>> > > Thanks,
>>> > >
>>> > > Jun
>>> > >
>>> > > On Wed, Jun 1, 2011 at 2:18 PM, Fournier, Camille F. [Tech] <
>>> > > [EMAIL PROTECTED]> wrote:
>>> > >
>>> > >> All clients are in different processes?
>>> > >> I've used zkclient and haven't seen any problems, but I haven't
>>> hammered
>>> > it
>>> > >> too hard yet. I took a long look at the code and didn't see any
>>> errors
>>> > but
>>> > >> there could always be something very subtle.
>>> > >>
>>> > >> -----Original Message-----
>>> > >> From: Jun Rao [mailto:[EMAIL PROTECTED]]
>>> > >> Sent: Wednesday, June 01, 2011 4:09 PM
>>> > >> To: [EMAIL PROTECTED]
>>> > >> Subject: Re: lost ZK events across datacenters
>>> > >>
>>> > >> I am using the zkclient package (
>>> > >> https://github.com/sgroschupf/zkclient.git).
>>> > >> The watcher code seems reasonable. Basically, each watcher event is
>>> > first
>>> > >> added to a queue. A separate event thread dequeues each event and
>>> reads
>>> > the
>>> > >> children of a path (which re-registers the watcher) and invokes the
>>> > >> registered listener.
>>> > >>
>>> > >> Anybody knows any issues in zkclient?
>>> > >>
>>> > >> Thanks,
>>> > >>
>>> > >> Jun
>>> > >>
>>> > >> On Wed, Jun 1, 2011 at 12:04 PM, Ted Dunning <[EMAIL PROTECTED]>
>>> > >> wrote:
>>> > >>
>>> > >> > This is most commonly due, in my own history of programming errors,
>>> to
>>> > >> > writing code that has a race window in it.  It is conceivable that
>>> > cross
>>> > >> > data-center operation would make such a race more of a problem.
>>> > >> >
>>> > >> > Can you say a bit about your code?  Did you make sure to use
>>> standard
>>> > >> > idioms
>>> > >> > as opposed to setting the watch in a different call from reading
>>> the
>>> > >> data?
>>> > >> >
>>> > >> > On Wed, Jun 1, 2011 at 11:40 AM, Jun Rao <[EMAIL PROTECTED]> wrote:
>>> > >> >
>>> > >> > > Hi,
>>> > >> > >
>>