callbacks.rb

# With thanks to https://github.com/optoro/activerecord-callback_notification for original inspiration
if Rails.env.development?
  module ActiveRecord
    module CallbackNotifications
      extend ActiveSupport::Concern

      module ClassMethods

        def notify_all_callbacks
          # Make sure all models are loaded before trying to enumerate
          Dir.glob(File.join(Rails.root, 'app/models/*.rb')).each { |file| require file }
          ActiveRecord::Base.send(:subclasses).each do |model|
            notify_callbacks_for_class(model)
          end
        end

        def notify_callbacks_for_class(klass)
          class_instance_methods = klass.public_instance_methods(false) +
            klass.protected_instance_methods(false) +
            klass.private_instance_methods(false)
          [:_create_callbacks, :_update_callbacks, :_save_callbacks].each do |callback_type|
            klass.send(callback_type).map(&:filter).each do |callback|
              # Ignore callbacks added by Rails
              next unless class_instance_methods.include?(callback)
              next if callback.to_s =~ /^autosave_/
              callback_method = "#{callback}_with_instrumentation"
              next if klass.respond_to?(callback_method)
              puts "instrumenting #{callback}"
              klass.class_eval {
                define_method callback_method do |&block|
                  ActiveSupport::Notifications.instrument("callback:#{callback}",
                                                          :object => self,
                                                          :callback => callback
                                                         )
                  "#{callback}_without_instrumentation"
                end
                klass.alias_method_chain callback, :instrumentation
              }
            end
          end
        end
      end
    end
  end

  ActiveRecord::Base.send(:include,  ActiveRecord::CallbackNotifications)

  # Set up callback notifications for all models
  ActiveRecord::Base.notify_all_callbacks

  # Or for individual models
  # ActiveRecord::Base.notify_callbacks_for_class(Beverage)

  # Subscribe to notifications to show in Rails log
  ActiveSupport::Notifications.subscribe(/^callback:/) do |*data|
    return unless ActiveRecord::Base.logger.debug?
    name = data.first
    event_details = data.last
    callback_object = event_details[:object]
    ActiveRecord::Base.logger.debug "  #{name}  [ #{callback_object.class} #{callback_object.id} ]"
  end

end