benchmark_controller_callback.rb

require "action_pack"
require "action_controller"
require "rails"

ENV["RAILS_ENV"] = "production"
ENV["SECRET_KEY_BASE_DUMMY"] = "1"

N = ENV.fetch("N", 1000).to_i
M = ENV.fetch("M", 50).to_i

class ApplicationController < ActionController::Base
  around_action { |_controller, action| action.call }

  unless ENV["NO_CALLBACK"]
    M.times do |i|
      class_eval <<~RUBY
      def foo#{i}; end
      before_action :foo#{i}
      RUBY
    end
  end
end

N.times do |i|
  controller = Class.new(ApplicationController) do
    def bar; end
    before_action :bar

    def index
      head :ok
    end
  end
  Object.const_set(:"Foo#{i}Controller", controller)
end

#pp MyController.__callbacks

class MyApp < Rails::Application
  config.load_defaults "7.1"
  config.eager_load = true
  config.cache_classes = true
  config.hosts << ->(_) { true }
  config.consider_all_requests_local = true
  config.public_file_server.enabled = false
  config.cache_store = :null_store

  config.log_level = :warn

  routes.append do
    N.times do |i|
      get "/foo#{i}", to: "foo#{i}#index"
    end
  end
  initialize!
end

def rss
  Integer(`ps -q #{$$} -o rss=`.strip)
end

GC.start
before = GC.stat(:heap_live_slots)
rss_before = rss
puts "live objects before: #{before}"
puts "RSS before: #{rss_before}"

# Warm the applcation: make one request to each controller
app = Rails.application
N.times do |i|
  env = Rack::MockRequest.env_for("http://example.org/foo#{i}")
  status, headers, body = app.call(env)
  body.close if body.respond_to?(:close)
end

GC.start
GC.start
GC.start
after = GC.stat(:heap_live_slots)
rss_after = rss
puts
puts "live objects after: #{after}"
puts "RSS after: #{rss_after}"
puts
puts "object delta: #{after - before}"
puts "RSS delta: #{rss_after - rss_before}"