Breakout HTTP calls to specified domains in Scout

net_http_with_domain.rb

# This modification provides more fine-grained visiblity of HTTP calls within Scout, breaking out time spent in HTTP calls for specified domains. 
#
# Instructions:
# 1. `bundle update scout_apm`. Older versions of `scout_apm` have a bug w/disabling instrumentation.
# 
# 2. Disable Scout's default HTTP instrumentation:
# config/scout_apm.yml
# production:
#   <<: *defaults
#   disabled_instruments: ['NetHttp']
#
# 3. Specify domains to display in Scout's overview charts in +SCOUT_HTTP_DOMAINS+. Those that don't appear will be aggregrated under "HTTP",
# which is the default behavior of the NetHttp instrument.

# If the domain is included in +SCOUT_HTTP_DOMAINS+, it will be listed seperately in Scout's timeseries charts.
# A reasonable breakout limit is ~5 unique domains.
SCOUT_HTTP_DOMAINS = ['api.statuspage.io', 'github.com', 'api.authy.com']

if !ScoutApm::Agent.instance.instrument_manager.installed_instruments.any? { |instance| instance.is_a?(ScoutApm::Instruments::NetHttp) }
  
  ScoutApm::Agent.instance.logger.info "Installing NetHttpWithDomain instrument."

  ::Net::HTTP.class_eval do
    include ScoutApm::Tracer

    def request_with_scout_instruments(*args,&block)
      self.class.instrument(scout_bucket(@address), "request", :ignore_children => true, :desc => request_scout_description(args.first)) do
        request_without_scout_instruments(*args, &block)
      end
    end

    def scout_bucket(address)
      SCOUT_HTTP_DOMAINS.any? { |domain| address == domain } ? address : 'HTTP'
    end

    def request_scout_description(req)
      path = req.path
      path = path.path if path.respond_to?(:path)

      max_length = ScoutApm::Agent.instance.context.config.value('instrument_http_url_length')
      (@address + path.split('?').first)[0..(max_length - 1)]
    end

    alias request_without_scout_instruments request
    alias request request_with_scout_instruments
  end

else

  ScoutApm::Agent.instance.logger.info "NOT installing NetHttpWithDomain instrument. NetHttp instrument isn't disabled."

end