Add http.route tag to rack

lib/datadog/tracing/contrib/grape/endpoint.rb

@@ -101,6 +101,9 @@ def endpoint_run(name, start, finish, id, payload)
 
                 span.set_tag(Tracing::Metadata::Ext::HTTP::TAG_METHOD, request_method)
                 span.set_tag(Tracing::Metadata::Ext::HTTP::TAG_URL, path)
+
+                # TEMP REMOVE ONCE SENT TO RACK // ENSURE APPLICATION ROOT IS PREPENDED IN RACK VIA URL#
+                span.set_tag(Tracing::Metadata::Ext::HTTP::TAG_ROUTE, extract_root(endpoint.env['REQUEST_URI'], path))
               ensure
                 span.start(start)
                 span.finish(finish)
@@ -192,6 +195,12 @@ def endpoint_run_filters(name, start, finish, id, payload)
 
             private
 
+            def extract_root(url, path)
+              parts = path.split('/').reject(&:empty?)
+              root = url.slice(0, url.index(parts.first))
+              parts.join('/').prepend(root)
+            end
+
             def api_view(api)
               # If the API inherits from Grape::API in version >= 1.2.0
               # then the API will be an instance and the name must be derived from the base.

lib/datadog/tracing/contrib/rails/ext.rb

@@ -12,6 +12,10 @@ module Ext
           ENV_ANALYTICS_ENABLED = 'DD_TRACE_RAILS_ANALYTICS_ENABLED'
           ENV_ANALYTICS_SAMPLE_RATE = 'DD_TRACE_RAILS_ANALYTICS_SAMPLE_RATE'
           ENV_DISABLE = 'DISABLE_DATADOG_RAILS'
+          SPAN_ROUTE = 'rails.route'
+          TAG_ROUTE_PATH = 'rails.route.path'
+          TAG_COMPONENT = 'rails'
+          TAG_OPERATION_ROUTING = 'routing'
         end
       end
     end

lib/datadog/tracing/contrib/rails/patcher.rb

@@ -5,11 +5,51 @@
 require_relative 'middlewares'
 require_relative 'utils'
 require_relative '../semantic_logger/patcher'
+require_relative 'ext'
 
 module Datadog
   module Tracing
     module Contrib
       module Rails
+        # Patcher to begin span on Rails routing
+        module RoutingRouteSetPatch
+          def call(*)
+            result = nil
+
+            configuration = Datadog.configuration.tracing[:rails]
+
+            Tracing.trace(
+              Ext::SPAN_ROUTE,
+              service: configuration[:service_name],
+              span_type: Tracing::Metadata::Ext::HTTP::TYPE_INBOUND,
+            ) do |span|
+              span.set_tag(Tracing::Metadata::Ext::TAG_COMPONENT, Ext::TAG_COMPONENT)
+              span.set_tag(Tracing::Metadata::Ext::TAG_OPERATION, Ext::TAG_OPERATION_ROUTING)
+              result = super
+            end
+
+            result
+          end
+        end
+
+        # Patcher to trace rails routing done by JourneyRouter
+        module JourneyRouterPatch
+          def find_routes(*)
+            result = super
+
+            if (span = Datadog::Tracing.active_span)
+              datadog_route = result.first[2].path.spec.to_s
+
+              span.resource = datadog_route.to_s
+
+              # TEMP REMOVE ONCE SENT TO RACK #
+              span.set_tag(Tracing::Metadata::Ext::HTTP::TAG_ROUTE, datadog_route)
+            end
+
+            result
+          end
+        end
+
         # Patcher enables patching of 'rails' module.
         module Patcher
           include Contrib::Patcher
@@ -41,6 +81,9 @@ def before_initialize(app)
               # Sometimes we don't want to activate middleware e.g. OpenTracing, etc.
               add_middleware(app) if Datadog.configuration.tracing[:rails][:middleware]
 
+              ActionDispatch::Routing::RouteSet.prepend(RoutingRouteSetPatch)
+              ActionDispatch::Journey::Router.prepend(JourneyRouterPatch)
+
               Rails::LogInjection.configure_log_tags(app.config)
             end
           end

lib/datadog/tracing/contrib/sinatra/tracer.rb

@@ -65,6 +65,9 @@ def route_eval
                 span.set_tag(Tracing::Metadata::Ext::TAG_COMPONENT, Ext::TAG_COMPONENT)
                 span.set_tag(Tracing::Metadata::Ext::TAG_OPERATION, Ext::TAG_OPERATION_ROUTE)
 
+                # TEMP REMOVE ONCE SENT TO RACK #
+                span.set_tag(Tracing::Metadata::Ext::HTTP::TAG_ROUTE, datadog_route)
+
                 trace.resource = span.resource
 
                 sinatra_request_span = Sinatra::Env.datadog_span(env)

lib/datadog/tracing/metadata/ext.rb

@@ -86,6 +86,7 @@ module HTTP
           TYPE_TEMPLATE = 'template'
           TAG_CLIENT_IP = 'http.client_ip'
           HEADER_USER_AGENT = 'User-Agent'
+          TAG_ROUTE = 'http.route'
 
           # General header functionality
           module Headers

sig/datadog/tracing/metadata/ext.rbs

@@ -42,6 +42,7 @@ module Datadog
           ERROR_RANGE: ::Range[::Integer]
           TAG_BASE_URL: ::String
           TAG_METHOD: ::String
+          TAG_ROUTE: String
           TAG_STATUS_CODE: ::String
           TAG_USER_AGENT: ::String
           TAG_URL: ::String