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From Mike Malone <m...@simplegeo.com>
Subject Re: Memcached protocol?
Date Mon, 05 Apr 2010 21:34:17 GMT
On Mon, Apr 5, 2010 at 1:46 PM, Paul Prescod <paul@ayogo.com> wrote:

> On Mon, Apr 5, 2010 at 1:35 PM, Mike Malone <mike@simplegeo.com> wrote:
> >> That's useful information Mike. I am a bit curious about what the most
> >> common use cases are for atomic increment/decrement. I'm familiar with
> >> atomic add as a sort of locking mechanism.
> >
> > They're useful for caching denormalized counts of things. Especially
> things
> > that change rapidly. Instead of invalidating the counter whenever an
> event
> > occurs that would incr/decr the counter, you can incr/decr the cached
> count
> > too.
>
> Do you think that a future cassandra increment/decrement would be
> incompatible with those use cases?
>
> It seems to me that in that use case, an eventually consistent counter
> is as useful as any other eventually consistent datum.


An eventually consistent count operation in Cassandra would be great, and it
would satisfy all of the use cases I would typically use counts for in
memcached. It's just a matter of reconciling inconsistencies with a more
sophisticated operation than "latest write wins" (specifically, the
reconciliation operation should apply all incr/decr ops).

Mike

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