Instrument every method in a class for metrics

notification_printer.rb

ActiveSupport::Notifications.subscribe(/my_class$/) do |*args|
  event = ActiveSupport::Notifications::Event.new(*args)

  Rails.logger.warn "%7.2fms %s" % [event.duration, event.name]
end

notifications.rb

module Notifications
  extend ActiveSupport::Concern

  module ClassMethods
    def method_added(method_name)
      @methods ||= []
      return if @methods.include?(method_name) || method_name =~ /_old$/
      @methods << method_name

      class_eval %{alias #{method_name}_old #{method_name}}

      define_method(method_name) do |*args|
        ActiveSupport::Notifications.instrument("#{method_name}.#{self.class.name.underscore}") do
          send("#{method_name}_old", *args)
        end
      end
    end
  end
end