automated middleware instrumentation

lib/travis/api/app.rb

@@ -20,6 +20,7 @@ require 'metriks/librato_metrics_reporter'
 require 'travis/support/log_subscriber/active_record_metrics'
 require 'fileutils'
 require 'travis/api/v2/http'
+require 'travis/api/stack_instrumentation'
 
 # Rack class implementing the HTTP API.
 # Instances respond to #call.
@@ -75,6 +76,7 @@ module Travis::Api
 
     def initialize
       @app = Rack::Builder.app do
+        extend StackInstrumentation
         use(Rack::Config) { |env| env['metriks.request.start'] ||= Time.now.utc }
 
         Rack::Utils::HTTP_STATUS_CODES[420] = "Enhance Your Calm"

lib/travis/api/app/stack_instrumentation.rb

@@ -0,0 +1,42 @@
+require 'travis/api/app'
+
+class Travis::Api::App
+  module StackInstrumentation
+    class Middleware
+      def initialize(app, title = nil)
+        @app   = app
+        @title = title || "Rack: use #{app.class.name}"
+      end
+
+      def call(env)
+        instrument { @app.call(env) }
+      end
+
+      def instrument(&block)
+        return yield unless instrument?
+        ::Skylight.instrument(title: title, &block)
+      end
+
+      def instrument?
+        defined? ::Skylight
+      end
+    end
+
+    def use(*)
+      super(Middleware)
+      super
+    end
+
+    def run(app)
+      super Middleware.new(app, "Rack: run %p" % app.class)
+    end
+
+    def map(path, &block)
+      super(path) do
+        use(Middleware, "Rack: map %p" % path)
+        extend StackInstrumentation
+        instance_eval(&block)
+      end
+    end
+  end
+end