Refactored: Rack to use Datadog::Contrib::Integration. (#541)

lib/ddtrace.rb

@@ -61,7 +61,7 @@ def configure(target = configuration, opts = {})
 require 'ddtrace/contrib/mongodb/patcher'
 require 'ddtrace/contrib/mysql2/patcher'
 require 'ddtrace/contrib/racecar/patcher'
-require 'ddtrace/contrib/rack/patcher'
+require 'ddtrace/contrib/rack/integration'
 require 'ddtrace/contrib/rails/patcher'
 require 'ddtrace/contrib/rake/patcher'
 require 'ddtrace/contrib/redis/patcher'

lib/ddtrace/contrib/rack/configuration/settings.rb

@@ -0,0 +1,39 @@
+require 'ddtrace/contrib/configuration/settings'
+require 'ddtrace/contrib/rack/ext'
+
+module Datadog
+  module Contrib
+    module Rack
+      module Configuration
+        # Custom settings for the Rack integration
+        class Settings < Contrib::Configuration::Settings
+          DEFAULT_HEADERS = {
+            response: [
+              'Content-Type',
+              'X-Request-ID'
+            ]
+          }.freeze
+
+          option :application
+          option :distributed_tracing, default: false
+          option :headers, default: DEFAULT_HEADERS
+          option :middleware_names, default: false
+          option :quantize, default: {}
+          option :request_queuing, default: false
+
+          option :service_name, default: Ext::SERVICE_NAME, depends_on: [:tracer] do |value|
+            get_option(:tracer).set_service_info(value, Ext::APP, Datadog::Ext::AppTypes::WEB)
+            value
+          end
+
+          option :web_service_name, default: Ext::WEBSERVER_SERVICE_NAME, depends_on: [:tracer, :request_queuing] do |value|
+            if get_option(:request_queuing)
+              get_option(:tracer).set_service_info(value, Ext::WEBSERVER_APP, Datadog::Ext::AppTypes::WEB)
+            end
+            value
+          end
+        end
+      end
+    end
+  end
+end

lib/ddtrace/contrib/rack/ext.rb

@@ -0,0 +1,18 @@
+module Datadog
+  module Contrib
+    module Rack
+      # Rack integration constants
+      module Ext
+        APP = 'rack'.freeze
+        SERVICE_NAME = 'rack'.freeze
+        WEBSERVER_APP = 'webserver'.freeze
+        WEBSERVER_SERVICE_NAME = 'web-server'.freeze
+
+        RACK_ENV_REQUEST_SPAN = 'datadog.rack_request_span'.freeze
+
+        SPAN_HTTP_SERVER_QUEUE = 'http_server.queue'.freeze
+        SPAN_REQUEST = 'rack.request'.freeze
+      end
+    end
+  end
+end

lib/ddtrace/contrib/rack/integration.rb

@@ -0,0 +1,32 @@
+require 'ddtrace/contrib/integration'
+require 'ddtrace/contrib/rack/configuration/settings'
+require 'ddtrace/contrib/rack/patcher'
+
+module Datadog
+  module Contrib
+    module Rack
+      # Description of Rack integration
+      class Integration
+        include Contrib::Integration
+
+        register_as :rack, auto_patch: false
+
+        def self.version
+          Gem.loaded_specs['rack'] && Gem.loaded_specs['rack'].version
+        end
+
+        def self.present?
+          super && defined?(::Rack)
+        end
+
+        def default_configuration
+          Configuration::Settings.new
+        end
+
+        def patcher
+          Patcher
+        end
+      end
+    end
+  end
+end

lib/ddtrace/contrib/rack/middlewares.rb

@@ -1,6 +1,7 @@
 require 'ddtrace/ext/app_types'
 require 'ddtrace/ext/http'
 require 'ddtrace/propagation/http_propagator'
+require 'ddtrace/contrib/rack/ext'
 require 'ddtrace/contrib/rack/request_queue'
 
 module Datadog
@@ -15,6 +16,8 @@ module Rack
       # information available at the Rack level.
       # rubocop:disable Metrics/ClassLength
       class TraceMiddleware
+        # DEPRECATED: Remove in 1.0 in favor of Datadog::Contrib::Rack::Ext::RACK_ENV_REQUEST_SPAN
+        # This constant will remain here until then, for backwards compatibility.
         RACK_REQUEST_SPAN = 'datadog.rack_request_span'.freeze
 
         def initialize(app)
@@ -29,7 +32,7 @@ def compute_queue_time(env, tracer)
           return if request_start.nil?
 
           tracer.trace(
-            'http_server.queue',
+            Ext::SPAN_HTTP_SERVER_QUEUE,
             start_time: request_start,
             service: Datadog.configuration[:rack][:web_service_name]
           )
@@ -56,7 +59,7 @@ def call(env)
 
           # start a new request span and attach it to the current Rack environment;
           # we must ensure that the span `resource` is set later
-          request_span = tracer.trace('rack.request', trace_options)
+          request_span = tracer.trace(Ext::SPAN_REQUEST, trace_options)
           env[RACK_REQUEST_SPAN] = request_span
 
           # Add deprecation warnings

lib/ddtrace/contrib/rack/patcher.rb

@@ -3,63 +3,38 @@ module Contrib
     module Rack
       # Provides instrumentation for `rack`
       module Patcher
-        include Base
+        include Contrib::Patcher
 
-        DEFAULT_HEADERS = {
-          response: [
-            'Content-Type',
-            'X-Request-ID'
-          ]
-        }.freeze
+        module_function
 
-        register_as :rack
-        option :tracer, default: Datadog.tracer
-        option :distributed_tracing, default: false
-        option :middleware_names, default: false
-        option :quantize, default: {}
-        option :application
-        option :service_name, default: 'rack', depends_on: [:tracer] do |value|
-          get_option(:tracer).set_service_info(value, 'rack', Ext::AppTypes::WEB)
-          value
-        end
-        option :request_queuing, default: false
-        option :web_service_name, default: 'web-server', depends_on: [:tracer, :request_queuing] do |value|
-          if get_option(:request_queuing)
-            get_option(:tracer).set_service_info(value, 'webserver', Ext::AppTypes::WEB)
-          end
-          value
+        def patched?
+          done?(:rack)
         end
-        option :headers, default: DEFAULT_HEADERS
-
-        module_function
 
         def patch
-          unless patched?
+          # Patch middleware
+          do_once(:rack) do
             require_relative 'middlewares'
-            @patched = true
           end
 
-          if (!instance_variable_defined?(:@middleware_patched) || !@middleware_patched) \
-             && get_option(:middleware_names)
+          # Patch middleware names
+          if !done?(:rack_middleware_names) && get_option(:middleware_names)
             if get_option(:application)
-              enable_middleware_names
-              @middleware_patched = true
+              do_once(:rack_middleware_names) do
+                patch_middleware_names
+              end
             else
               Datadog::Tracer.log.warn(%(
               Rack :middleware_names requires you to also pass :application.
               Middleware names have NOT been patched; please provide :application.
               e.g. use: :rack, middleware_names: true, application: my_rack_app).freeze)
             end
           end
-
-          @patched || @middleware_patched
+        rescue StandardError => e
+          Datadog::Tracer.log.error("Unable to apply Rack integration: #{e}")
         end
 
-        def patched?
-          @patched ||= false
-        end
-
-        def enable_middleware_names
+        def patch_middleware_names
           retain_middleware_name(get_option(:application))
         rescue => e
           # We can safely ignore these exceptions since they happen only in the
@@ -81,9 +56,16 @@ def call(env)
             end
           end
 
-          following = middleware.instance_variable_get('@app')
+          following = if middleware.instance_variable_defined?('@app')
+                        middleware.instance_variable_get('@app')
+                      end
+
           retain_middleware_name(following)
         end
+
+        def get_option(option)
+          Datadog.configuration[:rack].get_option(option)
+        end
       end
     end
   end

test/contrib/grape/rack_app.rb

@@ -50,7 +50,7 @@ def setup
   def teardown
     super
     # reset the configuration
-    Datadog.registry[:rack].reset_options!
-    Datadog.registry[:grape].reset_options!
+    Datadog.configuration[:rack].reset_options!
+    Datadog.configuration[:grape].reset_options!
   end
 end

test/contrib/rack/helpers.rb

@@ -116,6 +116,6 @@ def setup
   def teardown
     super
     # reset the configuration
-    Datadog.registry[:rack].reset_options!
+    Datadog.configuration[:rack].reset_options!
   end
 end

test/contrib/rack/resource_name_test.rb

@@ -13,8 +13,13 @@ def setup
       run BottomMiddleware.new
     end.to_app
 
-    remove_patch!(:rack)
-    Datadog.registry[:rack].instance_variable_set('@middleware_patched', false)
+    Datadog.registry[:rack].patcher.tap do |patcher|
+      if patcher.instance_variable_defined?(:@done_once)
+        patcher.instance_variable_get(:@done_once).delete(:rack)
+        patcher.instance_variable_get(:@done_once).delete(:rack_middleware_names)
+      end
+    end
+
     Datadog.configuration.use(
       :rack,
       middleware_names: true,