easy-going-rails/lib/semantic/instrumentation_manager.rb

module Semantic
  class InstrumentationManager
    NOTIFICATIONS = {
      action_controller: %i[start_processing process_action redirect_to],
      action_view: %i[render_partial render_template render_collection render_layout],
      active_record: %i[sql strict_loading instantiation start_transaction transaction]
    }.freeze

    def logger = @logger ||= SemanticLogger[:instrumentation]

    def initialize
      logger.debug 're-initialized'
    end

    def self.clear
      NOTIFICATIONS.each do |event_group, hooks|
        hooks.each { |hook| ActiveSupport::Notifications.unsubscribe("#{hook}.#{event_group}") }
      end
    end

    def process(changes)
      logger.info "process called with #{changes.size} change(s)"
      changes.each do |change|
        constant = change[:constant]
        value = change[:new_value]
        case constant
        when 'ACTION_VIEW', 'ACTION_CONTROLLER', 'ACTIVE_RECORD'
          value ? enable(constant) : disable(constant)
        end
      end
      logger.info 'DONE'
    end

    def enable(constant)
      logger.info("enable: #{constant}")
      event_group = constant.underscore.to_sym
      log_subscriber = build_log_subscriber_from(event_group.to_s.camelize)
      logger.warn(log_subscriber)

      NOTIFICATIONS[event_group].each do |hook|
        logger.info("subscribe to #{hook}.#{event_group}")
        ActiveSupport::Notifications.subscribe("#{hook}.#{event_group}") do |event|
          # logger.debug("SEND #{log_subscriber} hook=#{hook}")
          log_subscriber.send(hook, event)
        end
      end
    end

    def disable(constant)
      logger.info("disable: #{constant}")
      event_group = constant.underscore.to_sym

      logger.debug(NOTIFICATIONS[event_group].size)

      NOTIFICATIONS[event_group].each do |hook|
        logger.info("unsubscribe to #{hook}.#{event_group}")
        ActiveSupport::Notifications.unsubscribe("#{hook}.#{event_group}")
      end
    end

    def build_log_subscriber_from(classname)
      case classname
      when 'ActionController' then Semantic::Subscribers.const_get(classname).new('toto1')
      else Semantic::Subscribers.const_get(classname).new
      end
    end
  end
end