problem with module attribute keeping value over multiple Rails requests

foo.rb

#
# -=[ Problem ]=-
#
# On the first Rails request, after calling Foo.configure in 
# config/environments/development.rb, @@provider is the correct 
# object and so Foo.doit() succeeds. On the second request, though, 
# it raises the ArgumentError b/c @@provider is now nil. What am I
# doing wrong?
#
# This file lives in lib/foo.rb in a Rails 2.3.5 project 
# (RubyEE 1.8.7).
#
module Foo
  mattr_reader :provider

  def self.configure options={}
    @@provider = Foo::Bar.new(options)
  end

  def self.doit arg
    raise ArgumentError unless @@provider
    @@provider.doit(arg)
  end
end