Mongrel in JRuby?

I'm going to try to post more frequent, less-verbose entries to break up the time between longer articles. This is the first.

For those of you unfamiliar with it, Mongrel is a (mostly) Ruby HTTP 1.1 server, designed to escape the perils of cgi/fcgi/scgi when running web frameworks like Rails or Camping. From what I hear it's very fast and very promising. Think of it as a Ruby equivalent to Java's servlet/web containers like Jetty and Tomcat.

Deploying Rails apps under JRuby currently has only two reasonable outlets:

- You can wrap all the Rails-dispatching logic into a servlet, deploying as you would a web application.
- You can (mostly) run the "server" script, which starts up Rails in WEBrick, Ruby's builtin lightweight server framework.

The first option would obviously provide the best integration with existing Java code and infrastructure. The second is good for development-time testing.

However, with JRuby rapidly becoming production-usable, there will be many folks who want a third option: deploying Rails--just Rails--in a production environment without a meaty servlet engine. For Ruby, that's where Mongrel comes in.

Mongrel is by the developer's own admission "mostly" Ruby code. The one big area where it is not Ruby is in its HTTP parser library (there's also a native ternary search tree, but that's no big deal to reimplement). Using Mongrel, require 'http11' pulls in a C-based HTTP 1.1 parser and related utilities. Ruby is notoriously slow for parsing work, so this native code is not unreasonable. However, it would be a barrier to running Mongrel within JRuby; we would need our own native implementation of the http11 library.

So, any takers? If I had a nickle for every JRuby sub-project I want to work on I'd have a fistful of nickles. This one will probably be pretty far back in the queue.

Known possibilities for lightweight HTTP 1.1 support (really all that's needed for Mongrel is an HTTP1.1 library, but that can probably be used alone):

- Jetty
- Simple

For those of you that say "Why not just wire Rails into [Tomcat|Jetty|Simple] and be done with it" I have this answer: Rubyists are not particularly fond of Java libraries. My aim of late is working toward supporting both Ruby/Java folks who will happily marry the two and pure Ruby folks that simply want another runtime to use. Mongrel is bound to become a very popular choice for web serving Ruby applications, and we would be remiss if we did not attempt to support it.
Written on June 15, 2006