Instrument Grape Endpoint with Metrics::RackMiddleware

lib/gitlab/metrics/rack_middleware.rb

 module Gitlab
   module Metrics
-    # Rack middleware for tracking Rails requests.
+    # Rack middleware for tracking Rails and Grape requests.
     class RackMiddleware
       CONTROLLER_KEY = 'action_controller.instance'
+      ENDPOINT_KEY   = 'api.endpoint'
 
       def initialize(app)
         @app = app
@@ -21,6 +22,8 @@ module Gitlab
         ensure
           if env[CONTROLLER_KEY]
             tag_controller(trans, env)
+          elsif env[ENDPOINT_KEY]
+            tag_endpoint(trans, env)
           end
 
           trans.finish
@@ -42,6 +45,26 @@ module Gitlab
         controller   = env[CONTROLLER_KEY]
         trans.action = "#{controller.class.name}##{controller.action_name}"
       end
+
+      def tag_endpoint(trans, env)
+        endpoint = env[ENDPOINT_KEY]
+        path = endpoint_paths_cache[endpoint.route.route_method][endpoint.route.route_path]
+        trans.action = "Grape##{endpoint.route.route_method} #{path}"
+      end
+
+      private
+
+      def endpoint_paths_cache
+        @endpoint_paths_cache ||= Hash.new do |hash, http_method|
+          hash[http_method] = Hash.new do |inner_hash, raw_path|
+            inner_hash[raw_path] = endpoint_instrumentable_path(raw_path)
+          end
+        end
+      end
+
+      def endpoint_instrumentable_path(raw_path)
+        raw_path.sub('(.:format)', '').sub('/:version', '')
+      end
     end
   end
 end

spec/lib/gitlab/metrics/rack_middleware_spec.rb

@@ -31,6 +31,20 @@ describe Gitlab::Metrics::RackMiddleware do
 
       middleware.call(env)
     end
+
+    it 'tags a transaction with the method andpath of the route in the grape endpoint' do
+      route    = double(:route, route_method: "GET", route_path: "/:version/projects/:id/archive(.:format)")
+      endpoint = double(:endpoint, route: route)
+
+      env['api.endpoint'] = endpoint
+
+      allow(app).to receive(:call).with(env)
+
+      expect(middleware).to receive(:tag_endpoint).
+        with(an_instance_of(Gitlab::Metrics::Transaction), env)
+
+      middleware.call(env)
+    end
   end
 
   describe '#transaction_from_env' do
@@ -60,4 +74,19 @@ describe Gitlab::Metrics::RackMiddleware do
       expect(transaction.action).to eq('TestController#show')
     end
   end
+
+  describe '#tag_endpoint' do
+    let(:transaction) { middleware.transaction_from_env(env) }
+
+    it 'tags a transaction with the method and path of the route in the grape endpount' do
+      route    = double(:route, route_method: "GET", route_path: "/:version/projects/:id/archive(.:format)")
+      endpoint = double(:endpoint, route: route)
+
+      env['api.endpoint'] = endpoint
+
+      middleware.tag_endpoint(transaction, env)
+
+      expect(transaction.action).to eq('Grape#GET /projects/:id/archive')
+    end
+  end
 end