Automatically eager load all integrations when in Rails context

In production mode it's preferable to load all the code upfront
even if it means loading some code that won't be used.

This is because loading the code on demand cause the first request
to use it to be slower, and to flush various VM caches such
as the global constant cache. It also degrade Copy on Write
performance for forking setups.

lib/offsite_payments.rb

@@ -32,6 +32,11 @@ def self.integration(name)
     Integrations.const_get("#{name.to_s.downcase}".camelize)
   end
 
+  def self.eager_load!
+    Integrations.eager_load!
+    nil
+  end
+
   mattr_accessor :mode
   self.mode = :production
 
@@ -42,3 +47,5 @@ def self.test?
 
   CURRENCIES_WITHOUT_FRACTIONS = [ 'BIF', 'BYR', 'CLP', 'CVE', 'DJF', 'GNF', 'ISK', 'JPY', 'KMF', 'KRW', 'PYG', 'RWF', 'TWD', 'UGX', 'VND', 'VUV', 'XAF', 'XOF', 'XPF' ]
 end
+
+require "offsite_payments/railtie" if defined? Rails::Railtie

lib/offsite_payments/integrations.rb

@@ -10,5 +10,12 @@ module Integrations
       # Register for autoloading
       autoload integration_class, f
     end
+
+    def self.eager_load!
+      constants.each do |const_name|
+        const_get(const_name)
+      end
+      nil
+    end
   end
 end

lib/offsite_payments/railtie.rb

@@ -0,0 +1,7 @@
+module OffsitePayments
+  class Railtie < Rails::Railtie
+    config.before_eager_load do
+      config.eager_load_namespace << OffsitePayments
+    end
+  end
+end

test/test_helper.rb

@@ -9,6 +9,7 @@
 require 'json'
 require 'nokogiri'
 
+require 'active_support'
 require 'active_support/core_ext/integer/time'
 require 'active_support/core_ext/numeric/time'
 require 'active_support/core_ext/time/acts_like'