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Date: Tue, 3 May 2011 16:07:57 -0500
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Subject: observers in occasionally disconnected data centers
From: Ketan Gangatirkar <ketan@indeed.com>
To: user@zookeeper.apache.org
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Hi.  We're considering ZooKeeper for coordinating operations across
multiple data centers.  These data centers will occasionally be
disconnected.  We were planning on using observers in remote data
centers.  Our applications can survive being unable to *write* to
ZooKeeper, but they do need to be able to read from it, even if the
data were stale.

On further examination, it looks like observers must always be
connected to the quorum to function at all.  Is this correct?  Does
anyone have suggestions for how to work around this problem?  The
first thing that comes to mind is duplicating the required data in
some other local data store and falling back on that when the DC
becomes disconnected.  I imagine the disadvantages of that are obvious
to everyone.  I hope someone can share some great idea that allows me
to avoid that miserable fate.  Thanks.

-- 
Ketan Gangatirkar
ketan@indeed.com