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? >