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From Chang Song <tru64...@me.com>
Subject Persistent watch stream?
Date Sat, 13 Nov 2010 03:16:54 GMT


It's been a couple of weeks since we started integrating zookeeper into our app.
Great piece of software. Cut down LOC by more than half.
Thank you for open sourcing Zookeeper.

I have a couple of questions, though.
I was wondering you have any plan to support persistent watch stream feature?

One-time watch is very inconvenient for us.
We need to get a stream of notifications in order. We are talking thousands of clients.
Since notification can happen in bulk, we need to set a watch first, and once we get a callback,
we need to check periodically what happens to the children of the watch nodes.

You can consider this as a automatic server-side watch registration feature: I'd call this
sticky watch.
I think it is easier to implement this as a sticky watch.

Another question is if it is possible to coalesce predefined number of changes for watch callbacks.
We have observed that if there are many changes in children node, clients gets different number
messages in bulks. This makes the architecture of our application from event-driven to polling
for a while.
Thus pretty much the same reasoning behind the first question.

Any comments welcome.

Thank you.


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