Twitter's reliance on Ruby and Ruby on Rails proves the language's resilience.As the maker of one of the largest applications using Ruby on Rails on the Web,
Twitter knows a thing or two about scaling applications built with the popular
development framework.
Britt Selvitelle, a senior engineer at Twitter, offered a few tips and
tricks for scaling Ruby on Rails and expressed particular appreciation for the
Rails framework itself and the language is it based on, Ruby.
"For us, for a large part of our system, Ruby has been the tool that
fit," Selvitelle said. He said Twitter has primarily used Ruby and Rails
for its applications with a sprinkling of Erlang. "We're constantly
experimenting," he said.
Selvitelle said the Twitter development team prefers the Ruby environment,
although, "if we need to drop down to a lower-level language we are
prepared to, but we haven't had to." In the future, he said, "We
might have to optimize certain parts of the system with C++ or something, but
as of yet, we haven't had to."
As part of Twitter's strategy for scaling Rails, the company has taken
advantage of more hardware capacity via its Web hosting providerfirst Joyent
and later NTT Americaas a first resort to
accommodate increased volume.
Cache early and often
In addition to hardware capacity, Selvitelle said Twitter addresses the
issue of scaling Rails by caching early and often. In a talk on scaling Rails applications,
Selvitelle advised developers to abstract long-running processes to daemons and
"index everything you will query on, avoid complex joins, use joint
indices when you must join tables, and avoid scanning large sets of data,"
among a series of other tips.
Selvitelle said Twitter has gone from being a small side project at Obvious,
the San Francisco company that
launched Twitter, to becoming one of the most popular sites on the Web.
Click here to read about some startups that are focusing on scalability for Ruby on Rails.
"There are several layers; it's like peeling an onion," he said of
the levels of complexity involved in maintaining the Twitter site. And some of
the time things just don't work, as in some of the outages the company has had
over recent months. The company related a recent outage to "caching
changes" and others were said to be related to issues with Twitter's Web
hosting provider.
"The fact is we have more users and higher complexity," Selvitelle
said. "We have to balance how to keep the site performant and add new
features. There's a fine line between making your system robust and supporting
users."
Meanwhile, Ruby as the Twitter team's language of choice "is a
fantastic language, and here in our own South
Park neighborhood in San
Francisco we're lucky to be around some of the best
Ruby developers in the industry," Selvitelle said, speaking of Engine
Yard, a hosting service for Ruby and Rails applications.
"Ruby is a beautiful language and it's fun to write software in; it
gives us a lot of creativity," Selvitelle said. Ruby also has enabled the
Twitter development team to use agile development techniques, he said.
Moreover, the development team has been able to work
more efficiently because it eats its own dog food, Selvitelle said. "We
not only write the software, we use the software," he said, speaking of
the Twitter messaging Web 2.0 technology. "We use it all the time. Our
lives revolve around the technology."
Meanwhile,
despite Twitter's professed satisfaction with Ruby on Rails, there have been
recent reports that Twitter might be looking to abandon Rails because of
scalability issues. However, Twitter officials debunked the claim. First,
Obvious founder Evan Williams refuted the claim in a Twitter post, saying:
"FWIW: Twitter currently has no plans to abandon RoR. Lots of our code is
not in RoR, already, though. Maybe that's why people are confused."
Selvitelle told eWEEK that reports of Twitter abandoning
Rails are "Not true in any sense. We use Ruby as our primary language. We
have plenty of back-end architecture in other languages. Especially prototypes.
We still use Rails and have no plans to discontinue this in the future."
Application Development 
