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From Bryce Allen <bal...@ci.uchicago.edu>
Subject Re: How to reliably achieve unique constraints with Cassandra?
Date Fri, 06 Jan 2012 20:48:29 GMT
On Fri, 6 Jan 2012 10:03:38 -0800
Drew Kutcharian <drew@venarc.com> wrote:
> I know that this can be done using a lock manager such as ZooKeeper
> or HazelCast, but the issue with using either of them is that if
> ZooKeeper or HazelCast is down, then you can't be sure about the
> reliability of the lock. So this potentially, in the very rare
> instance where the lock manager is down and two users are registering
> with the same email, can cause major issues.

For most applications, if the lock managers is down, you don't acquire
the lock, so you don't enter the critical section. Rather than allowing
inconsistency, you become unavailable (at least to writes that require
a lock).

-Bryce

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