We asked ourselves a year ago if lighttpd 1.5.0 was vaporware. It seems that was nearly true. At that time, nginx, apache’s mod_proxy_balancer, and haproxy were flourishing as Rails proxy solutions. The more recent introduction of Phusion Passenger (mod_rails) and Ruby Enterprise Edition, both excellent, free, and open-source products, has now driven most deployments (including our own) away from proxying altogether.

There is—or was—generally two counter-arguments to Passenger. The first is the stability and performance argument, which is well understood and has been discussed at length. I believed it was well summarized by Engine Yard’s discussion on the topic. But this is not the argument I’m not interested in.

My early argument against mod_rails was complexity: first, by using Apache instead of a smaller, simpler web server, and second, using a platform that I don’t comprehend and can’t debug. This argument relates to an old article I wrote: that Rails applications—and applications in general—should act like a pipe. (The original article, by James Duncan Davidson, is so old its only accessible through archive.org). My presumption was that the same argument should apply to a 3rd-party mod_rails solution: I don’t know anything about the app server, so if I have problems, I’m screwed. How is this better than FastCGI?

It is ironic, then, to note the success of Passenger in light of Rails’ history with FastCGI. The reason, as it turns out, basically comes down to two answers:

1. Passenger is easy to set up under Apache, and requires less configuration than under nginx
2. Passenger always works, in my experience, and thus debugging problems is non-existent.
3. As a bonus, if you’re using something like monit to ensure your app stays up, monitoring apache2 is a lot easier than individual mongrel processes.

So, better products are better, and users (including myself) will flock to them once they realize it.

The Future

I do wonder, though, whether history will continue to repeat itself in this regard. Where will the next improvements be? What will be our theory (or justifications, as it seems to turn out) behind those improvements? Personally, I’ve been eying threaded solutions for a long time, and given that mod_rails is a multi-process solution, perhaps threads will move things forward in the future. However, given that Ruby 1.9 is still limited by the Global Interpreter Lock, we might not see a threaded answer for a while. The closest we’ll come in the short term is JRuby. Could it be possible that JRuby is the future? Only time will tell.