Scout Sneakers Instrumentation - see http://help.apm.scoutapp.com/#sneakers

scout_sneakers.rb

# A module for instrumenting Sneaker workers. 
#
# These can appear under "Background Jobs" (default) or "Web Endpoints" in the UI, depending on the value of 
# +SCOUT_TRANSACTION_TYPE+. 
#
# Appearing under "Web Endpoints" may be preferred if the app is only processing Sneaker
# transactions so that the app overview chart isn't blank.
#
# Example usage:
#
# class BaseWorker
#   include Sneakers::Worker

#   def work(attributes)
#     # Do work
#   end
#   # This MUST be included AFTER the work method is defined.
#   include ScoutApm::BackgroundJobIntegrations::Sneakers::Instruments
# end
module ScoutApm
  module BackgroundJobIntegrations
    class Sneakers
      module Instruments
        SCOUT_TRANSACTION_TYPE = 'Job' # Job | Controller
        def self.included(instrumented_class)
          ScoutApm::Agent.instance.logger.debug "Instrumenting #{instrumented_class.inspect}"
          instrumented_class.class_eval do
            unless instrumented_class.method_defined?(:work_without_scout_instruments)
              alias_method :work_without_scout_instruments, :work
              alias_method :work, :work_with_scout_instruments
            end
          end
        end

        def work_with_scout_instruments(*args)
          ensure_scout_started!
          req = ScoutApm::RequestManager.lookup

          started_queue = false

          if scout_job_transaction?
            req.start_layer(ScoutApm::Layer.new('Queue', @queue.name))
            started_queue = true
          end

          req.start_layer(ScoutApm::Layer.new(SCOUT_TRANSACTION_TYPE, scout_job_name))
          started_transaction = true

          begin
            work_without_scout_instruments(*args)
          rescue
            req.error!
            raise
          ensure
            req.stop_layer if started_transaction
            req.stop_layer if started_queue
          end
        end

        def scout_job_name
          self.class.to_s
        end

        def scout_job_transaction?
          SCOUT_TRANSACTION_TYPE == 'Job'
        end

        # Sneakers starts a number of worker processes. Ensure that a background worker is running
        # for this process so that metrics can be stored.
        def ensure_scout_started!
          unless ScoutApm::Agent.instance.background_worker_running?
            ScoutApm::Agent.instance.start(:skip_app_server_check => true)
            ScoutApm::Agent.instance.start_background_worker
          end
        end
      end
    end
  end
end