Re: Alex Payne (from twitter): Rails doesn't scale

> I'm taking the multiple-databases idea even one further: reading from
> external databases and dynamically *building* an AR heirarchy to ease access
> to that database (this is an administration site used to administer many
> websites).
>
> The real question needs to be: what server is he running? Is he using
> capistrano to help with distributed installs? I've heard good things about
> mongrel clusters and other bits of load balancing. Rails is most definitely
> scalable, it just may not be as easy as with other (read: older)
> technologies.
>
> Jason
>
> On 4/12/07, Richard Conroy <richard.con...@...> wrote:
>
>
>
> > On 4/12/07, Carl Lerche <carl.ler...@...> wrote:
>
> > > Ok Ok Ok... first off, I apologize for the sliiightly misleading
> > > subject line. But, I thought I'd try to draw some attention and see if
> > > I could get some discussion going (hopefully no flames though!).
>
> > > 1) "At this point in time there's no facility in Rails to talk to more
> > > than one database at a time."
>
> > I have seen Rails deployments that use multiple databases, theres
> > an illustration of one on the Ruby on Rails site for a german web
> > community.
>
> > Basically there is two databases, each is attached to a farm
> > of Rails Pizza boxes. Each Pizza box can only ever see one DB,
> > but the DBs increment their PKs in 2s (one is even the other odd),
> > so that they can periodically replicate/merge their data sets.
>
> > In principle you could use multiple DBs and scale horizontally,
> > but replication overhead will probably eat into you very quickly.
>
> > > 2) "setting up multiple read-only slave databases [is not a quick fix
> > > to implement]"
>
> > > 3) Ruby + Rails' syntactical sugar = slow
>
> > > Point #3 is pretty well known, the solutions always mentioned before
> > > is scale out. However, Alex says that they can't because of 1 & 2.
> > > I've been under the impression (and still am) that doing 1 & 2 really
> > > isn't that hard.
>
> > Well there are different options for 2. I am quite sure that you actually
> > spend lots of money on your DB to achieve it.
>
> > He did say or imply though that scaling out incurs additional DB overhead
> > per Rails instance. Which implies an optimal ratio between DBs & Rails
> > instances.
>
> > > So, the question is, what to do if you have a rails app and are in
> > > twitters place?
>
> > Pretty much what he is doing already. But then, its not like scaling is
> > easy in
> > the first place.
>
> > You have to ask yourself though - Twitter got up and running in ~ 9-12
> > months or so?
> > In a Java/.NET version would he even be in production by now? How would
> > the PHP
> > equivalent fare?