Add Dalli instrumentation to Skylight

config.ru

@@ -32,12 +32,31 @@ end
 
 if ENV['SKYLIGHT_APPLICATION']
   require 'skylight'
+  require 'skylight/probes/net_http'
   require 'logger'
   config = Skylight::Config.load(nil, ENV['RACK_ENV'], ENV)
   config['root'] = File.expand_path('..', __FILE__)
   config['agent.sockfile_path'] = File.expand_path('../tmp', __FILE__)
   config.logger = Logger.new(STDOUT)
   config.validate!
+
+  class DalliProbe
+    def install
+      %w[get get_multi set add incr decr delete replace append prepend].each do |method_name|
+        next unless Dalli::Client.method_defined?(method_name.to_sym)
+        Dalli::Client.class_eval <<-EOD
+          alias #{method_name}_without_sk #{method_name}
+          def #{method_name}(*args, &block)
+            Skylight.instrument(category: "api.memcache.#{method_name}", title: "Memcache #{method_name}") do
+              #{method_name}_without_sk(*args, &block)
+            end
+          end
+        EOD
+      end
+    end
+  end
+  Skylight::Probes.register("Dalli::Client", "dalli", DalliProbe.new)
+
   Skylight.start!(config)
 
   use Skylight::Middleware