Posted on 2011-07-10 00:40 leekiang
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how RoR scales
I've said it before, but it bears repeating: There's nothing interesting about how Ruby on Rails scales
We've gone the easy route and merely followed what makes Yahoo!,
LiveJournal, and other high-profile LAMP stacks scale high and mighty.
state out of the application servers and push it to
database/memcached/shared network drive (that's the whole Shared Nothing
thang). Use load balancers between your tiers, so you have load
balancers -> web servers -> load balancers -> app servers ->
load balancers -> database/memcached/shared network drive servers.
(Past the entry point, load balancers can just be software, like
In a setup like that, you can add almost any number of web and app servers without changing a thing.
the database is the "hard part", but still a solved problem. Once you
get beyond what can be easily managed by a decent master-slave setup
(and that'll probably take millions and millions of pageviews per day),
you start doing partitioning.
1-100K on cluster A, 100K-200K on cluster B, and so on. But again, this
is nothing new. LiveJournal scales like that. I hear eBay too. And
probably everyone else that has to deal with huge numbers.
the scaling part is solved. What's left is judging whether the
economics of it are sensible to you. And that's really a performance
issue, not a scalability one.
your app server costs $500 per month (like our dual xeons does) and can
drive 30 requests/second on Rails and 60 requests/second on
Java/PHP/.NET/whatever (these are totally arbitrary numbers
pulled out of my...), then you're faced with the cost of $500 for 2.6
million requests/day on the Rails setup and $250 for the same on the
How much is productivity worth to you? Let's just take a $60K/year
programmer. That's $5K/month. If you need to handle 5 million
requests/day, your programmer needs to be 10% more productive on Rails
to make it even. If he's 15% more productive, you're up $250. And this
is not even considering the joy and happiness programmers derive from
working with more productive tools (nor that people have claimed to be
many times more productive).
Of course, the silly math above hinges on the assumption that the whateverstack
is twice as fast as Rails. That's a very big if. And totally dependent
on the application, the people, and so on. Some have found Rails to be as fast or faster than comparable "best-of-breed J2EE stacks".
point is that the cost per request is plummeting, but the cost of
programming is not. Thus, we have to find ways to trade efficiency in
the runtime for efficiency in the "thought time" in order to make the
development of applications cheaper. I believed we've long since entered
an age where simplicity of development and maintenance is where the
real value lies.