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

module Semantic
  class LogSubscriber < ActiveSupport::LogSubscriber
    include SemanticLogger::Loggable
    # def logger = SemanticLogger['Rails']

    EMPTY = 'none'.freeze

    def initialize(session_key)
      @session_key = session_key
      @transactions = {}
      super()
    end

    def start_processing(event)
      session_value = session_value(event)
      @transactions[event.transaction_id] = session_value # preserve session_value to help finish_processing

      SemanticLogger.tagged(session_value) do
        request = event.payload[:request]
        logger.info("Started #{request.raw_request_method} #{request.filtered_path}")

        format = event.payload[:format]
        format = format.to_s.upcase if format.is_a?(Symbol)
        format = '*/*' if format.nil?
        logger.debug("Processing by #{event.payload[:controller]}##{event.payload[:action]} as #{format}")
      end
    end

    def finish_processing(event)
      session_value = @transactions.delete(event.transaction_id) # get previous session_value from start_processing
      SemanticLogger.tagged(session_value) do
        payload = event.payload
        additions = ActionController::Base.log_process_action(payload)
        status = payload[:status]

        if status.nil? && (exception_class_name = payload[:exception]&.first)
          status = ActionDispatch::ExceptionWrapper.status_code_for_exception(exception_class_name)
        end

        additions << "GC: #{event.gc_time.round(1)}ms"
        logger.debug("Processed in #{event.duration.round}ms (#{additions.join(' | ')})")
        logger.info("Completed #{status} #{Rack::Utils::HTTP_STATUS_CODES[status]}")
      end
    end

    private

    def session_value(event) = event.payload[:headers]['rack.session'].fetch(@session_key, EMPTY)
  end
end