Instrument Grape Endpoint with Metrics::RackMiddleware

Generating the following tags

Grape#GET /projects/:id/archive

from Grape::Route objects like

{ :path => /:version/projects/:id/archive(.:format)
  :version => “v3”,
  :method => “GET” }

Use an instance variable to cache raw_path transformations.
This variable is only going to growth to the number of 
endpoints of the API, not with exact different requests

We can store this cache as an instance variable because 
middleware are initialised only once

1 files changed, 24 insertions, 1 deletions

diff --git a/lib/gitlab/metrics/rack_middleware.rb b/lib/gitlab/metrics/rack_middleware.rb
index 6f179789d3e..3fe27779d03 100644
--- a/lib/gitlab/metrics/rack_middleware.rb
+++ b/lib/gitlab/metrics/rack_middleware.rb
@@ -1,8 +1,9 @@
 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