Peter's Blog

I want to use rails as the front end for an application that I am developing. The application requires that I maintain a persistant object, i.e. one that lives on between multiple page requests. Given that my application would live in a single mongrel instance, is there an easy way to do this?

Well, I studied the code in the mongrel/rails stack (open source ftw) and it turns out that it is easy. Once the rails framework is loaded by mongrel, the dispatcher will handle any request that comes in and once the request is completed it will reload rails own reloadable classes (controllers, models etc) so that they are 'clean' and ready for the next request.

It is very easy to have an object that survives between individual page requests.

Here is an object:

   1  class SillyCounter
   2    def initialize
   3      @count = 0
   4    end
   5  
   6    def Inc
   7      return @count += 1
   8    end
   9  end
  10  
  11  $oSillyCounter = SillyCounter.new

I put this in lib/SillyCounter.rb since I like CamelCase.

I load it in config/environment.rb, right at the bottom:

require 'lib/SillyCounter'

and in a view I added:

<p><%= $oSillyCounter.Inc %> pages served since last reboot</p>

Relaunch mongrel and it works!

CAVEAT: I'll emphasise that this will only work for a single process server! But my application is single user and will never need to serve 1000 requests/second! I would use dRb (distributed ruby) if I needed something scalable.

Todo: find a rails problem that takes more than 20 lines to get around.

PHP programmers out there may be interested to know that this is the first time I have used a $ in a variable name in ruby.