On Tue, May 4, 2010 at 3:45 PM, Ted Dunning <ted.dunn...@gmail.com> wrote:
> Travis,
>
> Attachments are stripped from this mailing list.  Can you file a JIRA and
> put your attachment on that instead?
>
> Here is a link to get you started:
> https://issues.apache.org/jira/browse/ZOOKEEPER

Whoops. Filed:

https://issues.apache.org/jira/browse/ZOOKEEPER-765

--travis


>
> On Tue, May 4, 2010 at 3:43 PM, Travis Crawford 
> <traviscrawf...@gmail.com>wrote:
>
>> Attached is a skeleton application I extracted from a script I use --
>> perhaps we could add this as a recipe? If there are issues I'm more
>> than happy to fix them, or add more comments, whatever. It took a
>> while to figure this out and I'd love to save others that time in the
>> future.
>>
>> --travis
>>
>>
>> On Tue, May 4, 2010 at 3:16 PM, Mahadev Konar <maha...@yahoo-inc.com>
>> wrote:
>> > Hi Adam,
>> >  I don't think zk is very very hard to get right. There are exmaples in
>> > src/recipes which implements locks/queues/others. There is ZOOKEEPER-22
>> to
>> > make it even more easier for application to use.
>> >
>> > Regarding re registration of watches, you can deifnitely write code and
>> > submit is as a part of well documented contrib module which lays out the
>> > assumptions/design of it. It could very well be useful for others. Its
>> just
>> > that folks havent had much time to focus on these areas as yet.
>> >
>> > Thanks
>> > mahadev
>> >
>> >
>> > On 5/4/10 2:58 PM, "Adam Rosien" <a...@rosien.net> wrote:
>> >
>> >> I use zkclient in my work at kaChing and I have mixed feelings about
>> >> it. On one hand it makes "easy things easy" which is great, but on the
>> >> other hand I very few ideas what assumptions it makes "under the
>> >> hood". I also dislike some of the design choices such as unchecked
>> >> exceptions, but that's neither here nor there. It would take some
>> >> extensive documentation work by the authors to really enumerate the
>> >> model and assumptions, but the project doesn't seem to be active
>> >> (either from it being adequate for its current users or just
>> >> inactive). I'm not sure I could derive the assumptions myself.
>> >>
>> >> I'm a bit frustrated that zk is "very, very hard to really get right".
>> >> At a project level, can't we create structures to avoid most of these
>> >> errors? Can there be a "standard model" with detailed assumptions and
>> >> implementations of all the recipes? How can we start this? Is there
>> >> something that makes this too hard?
>> >>
>> >> I feel like a recipe page is a big fail; wouldn't an example app that
>> >> uses locks and barriers be that much more compelling?
>> >>
>> >> For the common FAQ items like "you need to re-register the watch",
>> >> can't we just create code that implements this pattern? My goal is to
>> >> live up to the motto: a good API is impossible to use incorrectly.
>> >>
>> >> .. Adam
>> >>
>> >> On Tue, May 4, 2010 at 2:21 PM, Ted Dunning <ted.dunn...@gmail.com>
>> wrote:
>> >>> In general, writing this sort of layer on top of ZK is very, very hard
>> to
>> >>> get really right for general use.  In a simple use-case, you can
>> probably
>> >>> nail it but distributed systems are a Zoo, to coin a phrase.  The
>> problem is
>> >>> that you are fundamentally changing the metaphors in use so assumptions
>> can
>> >>> come unglued or be introduced pretty easily.
>> >>>
>> >>> One example of this is the fact that ZK watches *don't* fire for every
>> >>> change but when you write listener oriented code, you kind of expect
>> that
>> >>> they will.  That makes it really, really easy to introduce that
>> assumption
>> >>> in the heads of the programmer using the event listener library on top
>> of
>> >>> ZK.  Another example is how the atomic get content/set watch call works
>> in
>> >>> ZK is easy to violate in an event driven architecture because the
>> thread
>> >>> that watches ZK probably resets the watch.  If you assume that the
>> listener
>> >>> will read the data, then you have introduced a timing mismatch between
>> the
>> >>> read of the data and the resetting of the watch.  That might be OK or
>> it
>> >>> might not be.  The point is that these changes are subtle and tricky to
>> get
>> >>> exactly right.
>> >>>
>> >>> On Tue, May 4, 2010 at 1:48 PM, Jonathan Holloway <
>> >>> jonathan.hollo...@gmail.com> wrote:
>> >>>
>> >>>> Is there any reason why this isn't part of the Zookeeper trunk
>> already?
>> >>>>
>> >>>
>> >
>> >
>>
>

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