Return-Path: Delivered-To: apmail-cassandra-user-archive@www.apache.org Received: (qmail 29004 invoked from network); 22 Nov 2010 08:57:06 -0000 Received: from unknown (HELO mail.apache.org) (140.211.11.3) by 140.211.11.9 with SMTP; 22 Nov 2010 08:57:06 -0000 Received: (qmail 33980 invoked by uid 500); 22 Nov 2010 08:57:36 -0000 Delivered-To: apmail-cassandra-user-archive@cassandra.apache.org Received: (qmail 33833 invoked by uid 500); 22 Nov 2010 08:57:36 -0000 Mailing-List: contact user-help@cassandra.apache.org; run by ezmlm Precedence: bulk List-Help: List-Unsubscribe: List-Post: List-Id: Reply-To: user@cassandra.apache.org Delivered-To: mailing list user@cassandra.apache.org Received: (qmail 33825 invoked by uid 99); 22 Nov 2010 08:57:36 -0000 Received: from athena.apache.org (HELO athena.apache.org) (140.211.11.136) by apache.org (qpsmtpd/0.29) with ESMTP; Mon, 22 Nov 2010 08:57:36 +0000 X-ASF-Spam-Status: No, hits=2.9 required=10.0 tests=HTML_MESSAGE,RCVD_IN_DNSWL_NONE,SPF_NEUTRAL X-Spam-Check-By: apache.org Received-SPF: neutral (athena.apache.org: local policy) Received: from [209.85.215.44] (HELO mail-ew0-f44.google.com) (209.85.215.44) by apache.org (qpsmtpd/0.29) with ESMTP; Mon, 22 Nov 2010 08:57:29 +0000 Received: by ewy8 with SMTP id 8so3425070ewy.31 for ; Mon, 22 Nov 2010 00:57:07 -0800 (PST) MIME-Version: 1.0 Received: by 10.14.53.69 with SMTP id f45mr2681790eec.17.1290416227655; Mon, 22 Nov 2010 00:57:07 -0800 (PST) Received: by 10.14.127.5 with HTTP; Mon, 22 Nov 2010 00:57:07 -0800 (PST) X-Originating-IP: [80.179.102.198] In-Reply-To: <1290362216.7542.85.camel@erebus.lan> References: <1290362216.7542.85.camel@erebus.lan> Date: Mon, 22 Nov 2010 10:57:07 +0200 Message-ID: Subject: Re: Facebook messaging and choice of HBase over Cassandra - what can we learn? From: David Boxenhorn To: user@cassandra.apache.org Content-Type: multipart/alternative; boundary=90e6ba6150dedca3080495a0705c --90e6ba6150dedca3080495a0705c Content-Type: text/plain; charset=ISO-8859-1 It's true that Cassandra has "tunable consistency", but if eventual consistency is not sufficient for most of your use cases, Cassandra becomes much less attractive. Am I wrong? On Sun, Nov 21, 2010 at 7:56 PM, Eric Evans wrote: > On Sun, 2010-11-21 at 11:32 -0500, Simon Reavely wrote: > > As a cassandra user I think the key sentence for this community is: > > "We found Cassandra's eventual consistency model to be a difficult > > pattern to reconcile for our new Messages infrastructure." > > In my experience, "we needed strong consistency", in conversations like > these amounts to hand waving. It's the fastest way to shut down that > part of the discussion without having said anything at all. > > > I think it would be useful to find out more about this statement from > > Kannan and the facebook team. Does anyone have any contacts in the > > Facebook team? > > Good luck. Facebook is notoriously tight-lipped about such things. > > > My goal here is to understand usage patterns and whether or not the > > Cassandra community can learn from this decision; maybe even > > understand whether the Cassandra roadmap should be influenced by this > > decision to address a target user base. Of course we might also > > conclude that its just "not a Cassandra use-case"! > > Understanding is a laudable goal, just try to avoid drawing conclusions > (and call out others who are). > > > This is usually the point where a frenzy kicks in and folks assume that > the Smart Guys at Facebook know something they don't, something that > would invalidate their decision if they'd only known. > > I seriously doubt they've uncovered some Truth that would fundamentally > alter the reasoning behind *my* decision to use Cassandra, and so I plan > to continue as I always have. Following relevant research and > development, collecting experience (my own and others), and applying it > to the problems I face. > > > -- > Eric Evans > eevans@rackspace.com > > --90e6ba6150dedca3080495a0705c Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable
It's true that Cassandra has "tunable consistency= ", but if eventual consistency is not sufficient for most of your use = cases, Cassandra becomes much less attractive. Am I wrong?



On Sun, Nov 21, 2010 at 7:56 PM, Eric Evans <eevans@rackspace.= com> wrote:
On Sun, 2010-11-21 at 11:32 -0500, Simon Reavely wrote: > As a cassandra user I think the key sentence for this community is: > "We found Cassandra's eventual consistency model to be a diff= icult
> pattern to reconcile for our new Messages infrastructure."

In my experience, "we needed strong consistency", in conver= sations like
these amounts to hand waving. =A0It's the fastest way to shut down that=
part of the discussion without having said anything at all.

> I think it would be useful to find out more about this statement from<= br> > Kannan and the facebook team. Does anyone have any contacts in the
> Facebook team?

Good luck. =A0Facebook is notoriously tight-lipped about such things.=

> My goal here is to understand usage patterns and whether or not the > Cassandra community can learn from this decision; maybe even
> understand whether the Cassandra roadmap should be influenced by this<= br> > decision to address a target user base. Of course we might also
> conclude that its just "not a Cassandra use-case"!

Understanding is a laudable goal, just try to avoid drawing conclusio= ns
(and call out others who are).

<rant>
This is usually the point where a frenzy kicks in and folks assume that
the Smart Guys at Facebook know something they don't, something that would invalidate their decision if they'd only known.

I seriously doubt they've uncovered some Truth that would fundamentally=
alter the reasoning behind *my* decision to use Cassandra, and so I plan to continue as I always have. =A0Following relevant research and
development, collecting experience (my own and others), and applying it
to the problems I face.
</rant>

--
Eric Evans
eevans@rackspace.com


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