1 files changed, 49 insertions, 0 deletions
diff --git a/lib/gitlab/metrics/rack_middleware.rb b/lib/gitlab/metrics/rack_middleware.rb
new file mode 100644
index 00000000000..5c0587c4c51
--- /dev/null
+++ b/lib/gitlab/metrics/rack_middleware.rb
@@ -0,0 +1,49 @@
+module Gitlab
+  module Metrics
+    # Rack middleware for tracking Rails requests.
+    class RackMiddleware
+      CONTROLLER_KEY = 'action_controller.instance'
+
+      def initialize(app)
+        @app = app
+      end
+
+      # env - A Hash containing Rack environment details.
+      def call(env)
+        trans  = transaction_from_env(env)
+        retval = nil
+
+        begin
+          retval = trans.run { @app.call(env) }
+
+        # Even in the event of an error we want to submit any metrics we
+        # might've gathered up to this point.
+        ensure
+          if env[CONTROLLER_KEY]
+            tag_controller(trans, env)
+          end
+
+          trans.finish
+        end
+
+        retval
+      end
+
+      def transaction_from_env(env)
+        trans = Transaction.new
+
+        trans.add_tag(:request_method, env['REQUEST_METHOD'])
+        trans.add_tag(:request_uri, env['REQUEST_URI'])
+
+        trans
+      end
+
+      def tag_controller(trans, env)
+        controller = env[CONTROLLER_KEY]
+        label      = "#{controller.class.name}##{controller.action_name}"
+
+        trans.add_tag(:action, label)
+      end
+    end
+  end
+end