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Excerpts from Joshua Harlow's message of 2015-02-06 01:26:25 +0000:
> Angus Lees wrote:
> > On Fri Feb 06 2015 at 4:25:43 AM Clint Byrum <clint at fewbar.com
> > <mailto:clint at fewbar.com>> wrote:
> >     I'd also like to see consideration given to systems that handle
> >     distributed consistency in a more active manner. etcd and Zookeeper are
> >     both such systems, and might serve as efficient guards for critical
> >     sections without raising latency.
> >
> >
> > +1 for moving to such systems.  Then we can have a repeat of the above
> > conversation without the added complications of SQL semantics ;)
> >
> 
> So just an fyi:
> 
> http://docs.openstack.org/developer/tooz/ exists.
> 
> Specifically:
> 
> http://docs.openstack.org/developer/tooz/developers.html#tooz.coordination.CoordinationDriver.get_lock
> 
> It has a locking api that it provides (that plugs into the various 
> backends); there is also a WIP https://review.openstack.org/#/c/151463/ 
> driver that is being worked for etc.d.
> 

An interesting note about the etcd implementation is that you can
select per-request whether you want to wait for quorum on a read or not.
This means that in theory you could obtain higher throughput for most
operations which do not require this and then only gain quorum for
operations which require it (e.g. locks).