Hey, you got your Ruby in my Clojure!

UPDATE: This article is obsolete. See the Overlay Tutorial for current documentation and examples.

Recently, we've made some progress toward the promise of a polyglot application server. With the introduction of the Overlay project, it's now very easy to create a single app server capable of deploying both Ruby and Clojure (not to mention Java, of course) applications.

Laying TorqueBox over Immutant

The same Leiningen Immutant plugin that you use to install Immutant may be used to overlay the latest TorqueBox as well:

$ lein immutant overlay torquebox

And voila, your Immutant is suddenly also a TorqueBox! Now we need to set up your environment for TorqueBox development.

$ export TORQUEBOX_HOME=$HOME/.lein/immutant/current
$ export PATH=$TORQUEBOX_HOME/jruby/bin:$PATH

The TorqueBox distribution provides its own JRuby with the TorqueBox gems pre-installed. You can now use the torquebox command to deploy your Ruby applications to your Immutant!

Laying Immutant over TorqueBox

If you'd rather use your own JRuby, and you've already installed the torquebox-server gem, you can overlay the latest Immutant by cloning the Overlay project locally, installing Leiningen and running the following:

$ lein run :overlay $(torquebox env TORQUEBOX_HOME) immutant

All that's left is to set IMMUTANT_HOME and proceed as you normally would:

$ export IMMUTANT_HOME=$(torquebox env TORQUEBOX_HOME)

The Overlay project is capable of overlaying features from any JBoss AS7 distribution onto another one.

Convenient Combo-Pack

For your convenience, we've set up a job on our CI server to overlay the latest Immutant build atop the latest TorqueBox build whenever either is updated. So you can be on the bleeding edge of both projects by downloading and extracting this link:


Set both TORQUEBOX_HOME and IMMUTANT_HOME to the extracted directory, and...

Get Your Polyglot On!

Your overlaid server may be started however you're comfortable: either using the Leiningen Immutant plugin, the TorqueBox command or even the standard JBoss commands. It will start up all the apps you've deployed to it, regardless of their language.

If you have any trouble at all, please drop by #torquebox or #immutant on freenode, and we'll get you going.

WTF is an enterprise-grade app server?

That's a great question. We get it a lot. It was asked on Hacker News in response to our birth announcement of Immutant yesterday.

So as someone who has worked in multiple enterprises, and now works for a company whose primary customers are enterprises, and since I routinely toss around the term like everyone knows what it means, and since it's one of those awful terms that means something different to everyone...

I'm compelled to answer the question, "WTF is an enterprise-grade application server?"

The answer requires answering another question first:

What's an Enterprise?

Here's my definition: it's an organization of mostly-independent teams building and maintaining applications used by other internal groups and external customers.

The key identifier of an enterprise is "a group of groups" in which more than one of them builds software.

There's usually a single "system operations" group. Their life is hell. They're ultimately responsibile for the security and integrity of the organization's data and the lifecycles of all the applications built for and used by all the other groups in the organization.

Did I mention their life is hell?

They can't afford to support all the myriad databases, message queues and web frameworks each team might decide to build their apps around. Not to mention supporting multiple languages! They prefer a single, "all in the tin" solution. Sadly, that usually means .Net or Java.

So enterprise-grade implies a capacity for supporting these types of environments. It usually involves, among other things, messaging so that the disparate apps may communicate, transactions to ensure the integrity of distributed data stores, and clustering, not only for scalability, but also to allow the lifecycles of the multiple versions of the apps to vary independently. And oh yeah, it also has to stay up, all the time.

What's an App Server?

An app server is a single product that provides all those services. It's a multi-threaded process that, once started, provides any app deployed to it with a web server, messaging, transactions, scheduling, security, caching, clustering, and more. JBoss AS7 is one such app server. It's open-source and it's fast.

Unfortunately, most popular commercial Java app servers provide those robust enterprise services at a very high price. Not only in dollars, but in the form of complex Java API's, overly-configured slow implementations, vendor-negotiated standards and general "acronym soup".

But it doesn't have to be that way. The Rails "convention over configuration" mantra inspired the creation of TorqueBox, encapsulating the enterprise-grade services provided by JBoss AS7 behind simple Ruby API's. The immediate goal for Immutant is to do the same with Clojure.

But by integrating any JVM-based language with JBoss AS7, the ultimate goal is to keep all the groups in an enterprise -- both operations and development -- happy. Or at least significantly less soul-sucky and hopefully more productive.

But why should you care?

Maybe you shouldn't. Maybe you only need a web server and a database, maybe just a JVM! Maybe you're not in a group of groups. Heck, maybe you're not even in a group!

Maybe you're perfectly content being both developer and admin for your apps and the various external processes on which they depend, or you're quite happy delegating some of those responsibilities to the fine folks at Heroku, EngineYard, or someone else.

If that's the case, you are probably a very happy person, and I'm very happy for you!

But if you feel you could benefit from a more integrated "all in the tin" solution, and especially if you're thinking along polyglot lines, I think TorqueBox (and Immutant, once it matures) is a compelling alternative, whether you work in an enterprise or not.