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From lzwei <lllz...@gmail.com>
Subject subscription problem with Zookeeper
Date Tue, 03 Jan 2012 15:32:38 GMT
I'm a freshman to ZK. We're going to build a multiple mounted file
system, all clients shares a  centralized backend storage, with local
cache enabled. Since it is allow to read/write the backend file
concurrently, local data/meta data could be out-of-date, so the
subscription model is used to have notify data/meta-data changes,
other than check timestamp on each file access.

With ZK we could have threads watch znode for events and trigger
callbacks, but the lock granularity is a problem, the zk file
hierarchy represents exactly the same with our file system hierarchy,
but we can not watch all the znodes, is it possible for client
watching the one znode(for example the root znode), any changes on
child/low level znodes will notify clients, and envoke the callbacks.
It means only one watcher required for a given file system, which
reduces watchers dramatically.

Thanks a lot.

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