Heroku Secondary DB connection

gistfile1.txt

# config/application.rb
module MyApp
  class Application < Rails::Application
    ... other configs

    config.secondary_database_url = ENV['SECONDARY_DB_URL']
  end
end
We may want to override this in development / test

# config/environments/development.rb

module MyApp
  class Application < Rails::Application
    ... other configs

    config.secondary_database_url = 'SOME_CONNECTION_STRING'
  end
end    
Now to setup the class we'll have our models inherit from...

# lib/active_record/secondary.rb 
module ActiveRecord
  class Secondary < ActiveRecord::Base
    url = URI.parse( MyApp::Application.config.secondary_database_url )
    establish_connection(
      :adapter  => 'mysql',
      :host     => url.host,
      :username => url.userinfo.split(':')[0],
      :password => url.userinfo.split(':')[1],
      :database => url.path[1..-1],
      :port     => url.port || 3306
    )

  end

  class SecondaryMigration < ActiveRecord::Migration
    def connection
      ActiveRecord::Secondary.connection 
    end
  end

end