There is a world outside of Ruby on Rails

Well, these are all valid points, and this is precisely because Erlang is strong in all of these aspects that we ended up selecting it as our language of choice. Let’s digg a little further if you will.

Erlang is an obscure language
However you look at it, functional languages (Lisp, Haskell, Ocaml, Erlang) are less popular than your typical Ruby/Python/Java/C#. But who said the most popular language was the best ? (wouldn’t we all be programming in VB if this was the case :-) Maybe it is possible that there exists some hidden gems out there and it might be worth the time investigating these obscure languages. Notice that Paul Graham faced the exact same questions when he decided to go with Lisp for his startup in 98 !

If you pay close attention to the current trend in language development, you will notice that more and more functional programing features are making their way into procedural languages:

• the .each and .map operators in Ruby/Prototype (actually Javascript is more functional than you might think...)
• the clever use of blocks in Ruby (usually called closures in most other languages).

There is a reason for this: they do make programing easier (and not to forget the Python crowd, Erlang supports list comprehension. Sweet…) I cannot wait to see these languages adopt pattern matching (no, not your typical string regexp pattern matching, but the type which allows you to write a IPv4 header parses in just a few lines) . This is so elegant once you understand how it works…

One thing to be note though is that Erlang is not object oriented. This might seem like a small detail, but after having been taught for years that objects are the answer to every programing problem (including curing cancer and ending world hunger), it does require a little bit of an initial shift in your thought process…

Database support
Who needs Oracle/Mysql when you have Mnesia, a free, distributed, in memory database ? The ability to store native Erlang structures out of the box is so liberating: suddenly the need for your object-database mapping layer almost vanishes (well, not 100% to be fairly honest, but a big chunk of it: no need to create a 1-to-n relationship or a n-to-n relationship and a mapping table in many simple cases)

Not to mention that Mnesia supports table replication and is fully distributed, with the ability to add new ‘nodes’ on the fly. All of this out of the box ! (did I mention it was free too ?) This makes scaling up almost a joke. Compare this to the usual nightmares (and cost) of trying to implement a distributed Mysql/Oracle…

Developing environment/Debugger
This is where Erlang really shines. Remember that Erlang was initially created by Ericsson to ease the development of a highly scalable, fault tolerant telephony system. Not only did they create the language Erlang, they also came up with OTP (Open Telephony Platform). The name might be misleading: OTP is whole set of tools/libraries meant to make development in Erlang easier (and all of this is now open source)

The database Mnesia, for instance is part of OTP (and it comes with a graphical table explorer). Other tools, like a process explorer, and a graphical debugger are there as well. The ability to reload code on the fly is almost native to Erlang. And with a few lines of code you can do this across processes/machines (this starts becoming critical once your deployment infrastructure grows).

Also, OTP comes with what is known in Erlang world as gen_servers, which basically allows you to easily create synchronous and/or asynchronous services which can be called from any Erlang node. Another one of these hidden gems which makes your life way easier…

Community
The Erlang community is definitely smaller than the Ruby/Python communities, no doubt about this. But maybe this is not such a bad thing: small communities tend be more proactive in helping newcomers. People are more available (it’s not unusual to see Joe Armstrong, the father of Erlang, reply to your posts on the mailing lists…). It’s the same warm, small community feeling you experience when you get a Mac. Hard to describe though…

The best tool for the job
Let’s forget about languages for a second. Let’s look at what you really need to develop a scalable Web2.0 app. With Ajax being all over the place,  you start seeing the need to serve a lot of small requests (don’t render the whole page again, but only areas affected by your click. Single page apps are the new black !) This is where having a language explicitly designed to handle massive concurrent processes brings you a competitive advantage.

Look at our latest code push for instance. We just introduced the ability to have live review sessions for PowerPoint slides. You basically see other people currently reviewing the same presentation, you can leave real time notes and also have to ability to send quick IM messages. Think about what really happens in the background for a second. Because all of this is real time, every user is constantly going to the server asking “is there any new note/IM message to display” ? Now, we decided to go with a simple polling approach (== no Comet). This means we have to handle a lot of tiny requests/responses. This would be almost suicidal in any other language (or you would need to start adding plenty of servers to support any decent number of users). But not quite so in Erlang since the language was designed for this type of workload… It just scales beautifully (and yes, we still need to add extra servers as well to handle a large load, but just not as many…)

Here is a picture of what our app looks like (to fully appreciate the live functionality, you will have to sign up)

I could just go on and on about why I think Erlang is going to be a source of competitive advantage in the Web2.0 world. I am convinced we will start seeing more and more startups out there leveraging the power of massive concurrency. At the end of the day, the question you should be asking is not why WE are using Erlang, but why you are NOT using it ?

ps: just so that there is no confusion, this is not a RoR bashing article. I am myself a huge rails fan (and DHH is my hero, of course). But let’s keep in mind that rails is not the answer to everything…

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