add conditional skylight tracking

.gitignore

@@ -2,3 +2,4 @@ config/travis.yml
 .yardoc
 log/
 vendor
+config/skylight.yml

Gemfile

@@ -27,6 +27,7 @@ gem 'pry'
 gem 'metriks',         '0.9.9.6'
 gem 'metriks-librato_metrics', github: 'eric/metriks-librato_metrics'
 gem 'micro_migrations'
+gem 'skylight', '~> 0.6.0.beta.1'
 
 group :test do
   gem 'rspec',         '~> 2.13'

Gemfile.lock

@@ -81,7 +81,7 @@ GIT
 
 GIT
   remote: git://github.com/travis-ci/travis-yaml.git
-  revision: f3aa306016a08b66a487f966eb8aa3a60ee9b319
+  revision: 1630d576d221aea2340615e87f402df7889b5176
   specs:
     travis-yaml (0.2.0)
 
@@ -302,6 +302,8 @@ GEM
       rack-test
       sinatra (~> 1.4.0)
       tilt (~> 1.3)
+    skylight (0.6.0.beta.1)
+      activesupport (>= 3.0.0)
     slop (3.6.0)
     sprockets (2.2.3)
       hike (~> 1.2)
@@ -367,6 +369,7 @@ DEPENDENCIES
   sentry-raven!
   sinatra
   sinatra-contrib
+  skylight (~> 0.6.0.beta.1)
   travis-api!
   travis-config (~> 0.1.0)
   travis-core!

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/conditional_skylight'
 
 # Rack class implementing the HTTP API.
 # Instances respond to #call.

lib/travis/api/conditional_skylight.rb

@@ -0,0 +1,50 @@
+if ENV['SKYLIGHT_AUTHENTICATION']
+
+  require 'skylight/sinatra'
+  require 'tool/thread_local'
+  Skylight.start!
+
+  module Travis
+    module Api
+      module ConditionalSkylight
+        FEATURES        = Tool::ThreadLocal.new
+        CHECK_FREQUENCY = 120
+        NOT_JSON        = %r(\.(xml|png|txt|atom|svg)$)
+
+        module Middleware
+          ::Skylight::Middleware.send(:prepend, self)
+          def call(env)
+            if ConditionalSkylight.track?(env)
+              super(env)
+            else
+              t { "skipping middleware (condition not met)".freeze }
+              @app.call(env)
+            end
+          end
+        end
+
+        extend self
+
+        def track?(env)
+          return false unless feature_active? :skylight
+          return false if     feature_active? :skylight_json_only and env['PATH_INFO'.freeze] =~ NOT_JSON
+          true
+        end
+
+        def feature_active?(feature)
+          last_clear = Time.now.to_i - FEATURES[:last_clear].to_i
+
+          if last_clear > CHECK_FREQUENCY
+            FEATURES.clear
+            FEATURES[:last_clear] = Time.now.to_i
+          end
+
+          FEATURES.fetch(feature) { FEATURES[feature] = Travis::Features.feature_active?(feature) }
+        end
+      end
+    end
+  end
+
+else
+  Travis.logger.info('SKYLIGHT_AUTHENTICATION not set, skipping Skylight.')
+end