rails--rails/railties/lib/rails/application/bootstrap.rb

require "active_support/notifications"
require "active_support/descendants_tracker"

module Rails
  class Application
    module Bootstrap
      include Initializable

      initializer :load_environment_config do
        environment = config.paths.config.environments.to_a.first
        require environment if environment
      end

      initializer :load_active_support do
        require 'active_support/dependencies'
        require "active_support/all" unless config.active_support.bare
      end

      # Preload all frameworks specified by the Configuration#frameworks.
      # Used by Passenger to ensure everything's loaded before forking and
      # to avoid autoload race conditions in JRuby.
      initializer :preload_frameworks do
        ActiveSupport::Autoload.eager_autoload! if config.preload_frameworks
      end

      # Initialize the logger early in the stack in case we need to log some deprecation.
      initializer :initialize_logger do
        Rails.logger ||= config.logger || begin
          path = config.paths.log.to_a.first
          logger = ActiveSupport::BufferedLogger.new(path)
          logger.level = ActiveSupport::BufferedLogger.const_get(config.log_level.to_s.upcase)
          logger.auto_flushing = false if Rails.env.production?
          logger
        rescue StandardError => e
          logger = ActiveSupport::BufferedLogger.new(STDERR)
          logger.level = ActiveSupport::BufferedLogger::WARN
          logger.warn(
            "Rails Error: Unable to access log file. Please ensure that #{path} exists and is chmod 0666. " +
            "The log level has been raised to WARN and the output directed to STDERR until the problem is fixed."
          )
          logger
        end
      end

      # Initialize cache early in the stack so railties can make use of it.
      initializer :initialize_cache do
        unless defined?(RAILS_CACHE)
          silence_warnings { Object.const_set "RAILS_CACHE", ActiveSupport::Cache.lookup_store(config.cache_store) }

          if RAILS_CACHE.respond_to?(:middleware)
            config.middleware.insert_before("Rack::Runtime", RAILS_CACHE.middleware)
          end
        end
      end

      initializer :set_clear_dependencies_hook do
        unless config.cache_classes
          ActionDispatch::Callbacks.after do
            ActiveSupport::DescendantsTracker.clear
            ActiveSupport::Dependencies.clear
          end
        end
      end

      # Sets the dependency loading mechanism.
      # TODO: Remove files from the $" and always use require.
      initializer :initialize_dependency_mechanism do
        ActiveSupport::Dependencies.mechanism = config.cache_classes ? :require : :load
      end

      initializer :bootstrap_hook do |app|
        ActiveSupport.run_load_hooks(:before_initialize, app)
      end
    end
  end
end