Class: ScoutApm::Instant::Middleware

Inherits:
Object
  • Object
show all
Defined in:
lib/scout_apm/instant/middleware.rb

Overview

Note that this middleware never even gets inserted unless Rails environment is development (See Railtie)

Instance Method Summary collapse

Constructor Details

#initialize(app) ⇒ Middleware

Returns a new instance of Middleware.



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# File 'lib/scout_apm/instant/middleware.rb', line 43

def initialize(app)
  @app = app
end

Instance Method Details

#call(env) ⇒ Object 



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# File 'lib/scout_apm/instant/middleware.rb', line 47

def call(env)
  status, headers, response = @app.call(env)
  path, content_type = env['PATH_INFO'], headers['Content-Type']
  if ScoutApm::Agent.instance.config.value('dev_trace')
    if response.respond_to?(:body)
      req = ScoutApm::RequestManager.lookup
      slow_converter = LayerConverters::SlowRequestConverter.new(req)
      trace = slow_converter.call
      if trace
        metadata = {
            :app_root      => ScoutApm::Environment.instance.root.to_s,
            :unique_id     => env['action_dispatch.request_id'], # note, this is a different unique_id than what "normal" payloads use
            :agent_version => ScoutApm::VERSION,
            :platform      => "ruby",
        }
        hash = ScoutApm::Serializers::PayloadSerializerToJson.rearrange_slow_transaction(trace)
        hash.merge!(:metadata => metadata)
        payload = ScoutApm::Serializers::PayloadSerializerToJson.jsonify_hash(hash)

        if env['HTTP_X_REQUESTED_WITH'] == 'XMLHttpRequest' || content_type.include?("application/json")
          ScoutApm::Agent.instance.logger.debug("DevTrace: in middleware, dev_trace is active, and response has a body. This is either AJAX or JSON. Path=#{path}; ContentType=#{content_type}")
          # Add the payload as a header if it's an AJAX call or JSON
          headers['X-scoutapminstant'] = payload
          [status, headers, response]
        else
          # otherwise, attempt to add it inline in the page, along with the appropriate JS & CSS. Note, if page doesn't have a head or body,
          #duration = (req.root_layer.total_call_time*1000).to_i
          apm_host=ScoutApm::Agent.instance.config.value("direct_host")
          page = ScoutApm::Instant::Page.new(response.body)
          page.add_to_head(ScoutApm::Instant::Util.read_asset("xmlhttp_instrumentation.html")) # This monkey-patches XMLHttpRequest. It could possibly be part of the main scout_instant.js too. Putting it here so it runs as soon as possible.
          page.add_to_head("<link href='#{apm_host}/instant/scout_instant.css?cachebust=#{Time.now.to_i}' media='all' rel='stylesheet' />")
          page.add_to_body("<script src='#{apm_host}/instant/scout_instant.js?cachebust=#{Time.now.to_i}'></script>")
          page.add_to_body("<script>var scoutInstantPageTrace=#{payload};window.scoutInstant=window.scoutInstant('#{apm_host}', scoutInstantPageTrace)</script>")

          if response.is_a?(ActionDispatch::Response)
            ScoutApm::Agent.instance.logger.debug("DevTrace: in middleware, dev_trace is active, and response has a body. This appears to be an HTML page and an ActionDispatch::Response. Path=#{path}; ContentType=#{content_type}")
            # preserve the ActionDispatch::Response when applicable
            response.body=[page.res]
            [status, headers, response]
          else
            ScoutApm::Agent.instance.logger.debug("DevTrace: in middleware, dev_trace is active, and response has a body. This appears to be an HTML page but not an ActionDispatch::Response. Path=#{path}; ContentType=#{content_type}")
            # otherwise, just return an array
            [status, headers, [page.res]]
          end
        end
      else
        ScoutApm::Agent.instance.logger.debug("DevTrace: in middleware, dev_trace is active, and response has a body, but no trace was found. Path=#{path}; ContentType=#{content_type}")
        [status, headers, response]
      end
    else
      # don't log anything here - this is the path for all assets served in development, and the log would get noisy
      [status, headers, response]
    end
  else
    ScoutApm::Agent.instance.logger.debug("DevTrace: isn't activated via config. Try: SCOUT_DEV_TRACE=true rails server")
    [status, headers, response]
  end
end