cassandra-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Graham Sanderson <gra...@vast.com>
Subject Re: Realtime data and (C)AP
Date Sat, 10 Oct 2015 01:02:45 GMT
Most of our writes are not user facing so local_quorum is good... We also read at local_quorum
because we prefer guaranteed consistency... But we very quickly fall back to local_one in
the cases where some data fast is better than a failure. Currently we do that on a per read
basis but we could I suppose detect a pattern or just look at the gossip to decide to go en
masse into a degraded read mode

Sent from my iPhone

> On Oct 9, 2015, at 5:39 PM, Steve Robenalt <srobenalt@highwire.org> wrote:
> 
> Hi Brice,
> 
> I agree with your nit-picky comment, particularly with respect to the OP's emphasis,
but there are many cases where read at ONE is sufficient and performance is "better enough"
to justify the possibility of a wrong result. As with anything Cassandra, it's highly dependent
on the nature of the workload.
> 
> Steve
> 
> 
>> On Fri, Oct 9, 2015 at 12:36 PM, Brice Dutheil <brice.dutheil@gmail.com> wrote:
>>> On Fri, Oct 9, 2015 at 2:27 AM, Steve Robenalt <srobenalt@highwire.org>
wrote:
>>> 
>>> In general, if you write at QUORUM and read at ONE (or LOCAL variants thereof
if you have multiple data centers), your apps will work well despite the theoretical consistency
issues.
>> 
>> Nit-picky comment : if consistency is something important then reading at QUORUM
is important. If read is ONE then the read operation may not see important update. The safest
option is QUORUM for both write and read. Then depending on the business or feature the consistency
may be tuned.
>> 
>> — Brice
>> 
> 
> 
> 
> -- 
> Steve Robenalt 
> Software Architect
> srobenalt@highwire.org 
> (office/cell): 916-505-1785
> 
> HighWire Press, Inc.
> 425 Broadway St, Redwood City, CA 94063
> www.highwire.org
> 
> Technology for Scholarly Communication

Mime
View raw message