Add a fallback to inferred route for ApiSecurity::RouteExtractor

Author: y9v

lib/datadog/appsec/api_security/route_extractor.rb

@@ -1,5 +1,7 @@
 # frozen_string_literal: true
 
+require_relative '../../tracing/contrib/rack/route_from_path_inference'
+
 module Datadog
   module AppSec
     module APISecurity
@@ -60,13 +62,16 @@ def self.route_pattern(request)
               .recognize(request) { |route, _| break route.path.spec.to_s }
 
             # NOTE: If rails is unable to recognize request it returns empty Array
+            #       We want to return nil in that case to skip this request in the Sampler
             pattern = nil if pattern&.empty?
 
             # NOTE: If rails can't recognize the request, we are going to fallback
             #       to generic request path
             (pattern || request.path).delete_suffix(RAILS_FORMAT_SUFFIX)
           else
-            request.path
+            Tracing::Contrib::Rack::RouteFromPathInference.infer(request.path).tap do |inferred_route|
+              request.env[Tracing::Contrib::Rack::Ext::DATADOG_INFERRED_ROUTE] = inferred_route
+            end
           end
         end
       end

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

@@ -12,6 +12,7 @@ module Ext
           ENV_ANALYTICS_ENABLED = 'DD_TRACE_RACK_ANALYTICS_ENABLED'
           ENV_ANALYTICS_SAMPLE_RATE = 'DD_TRACE_RACK_ANALYTICS_SAMPLE_RATE'
           RACK_ENV_REQUEST_SPAN = 'datadog.rack_request_span'
+          DATADOG_INFERRED_ROUTE = 'datadog.inferred_route'
           SPAN_HTTP_PROXY_REQUEST = 'http.proxy.request'
           SPAN_HTTP_PROXY_QUEUE = 'http.proxy.queue'
           SPAN_REQUEST = 'rack.request'

sig/datadog/appsec/api_security/route_extractor.rbs

@@ -16,7 +16,7 @@ module Datadog
 
         RAILS_FORMAT_SUFFIX: String
 
-        def self.route_pattern: (APISecurity::_Request request) -> String
+        def self.route_pattern: (APISecurity::_Request request) -> String?
       end
     end
   end

sig/datadog/tracing/contrib/rack/ext.rbs

@@ -11,6 +11,8 @@ module Datadog
 
           RACK_ENV_REQUEST_SPAN: "datadog.rack_request_span"
 
+          DATADOG_INFERRED_ROUTE: ::String
+
           SPAN_HTTP_PROXY_REQUEST: "http.proxy.request"
 
           SPAN_HTTP_PROXY_QUEUE: "http.proxy.queue"

spec/datadog/appsec/api_security/route_extractor_spec.rb

@@ -104,7 +104,13 @@
         let(:route_set) { double('ActionDispatch::Routing::RouteSet', router: router) }
         let(:request) { double('Rack::Request', env: {}, script_name: '', path: '/users/1') }
 
-        it { expect(described_class.route_pattern(request)).to eq('/users/1') }
+        it { expect(described_class.route_pattern(request)).to eq('/users/{param:int}') }
+
+        it 'persists inferred route in the request env' do
+          expect { described_class.route_pattern(request) }
+            .to change { request.env[Datadog::Tracing::Contrib::Rack::Ext::DATADOG_INFERRED_ROUTE] }
+            .from(nil).to('/users/{param:int}')
+        end
       end
 
       context 'when route_uri_pattern is not set and request path_parameters is present' do
@@ -130,8 +136,8 @@
           let(:action_dispatch_request) { double('ActionDispatch::Request', env: {}, script_name: '', path: '/users/1') }
 
           it 'uses action dispatch request for route recognition' do
-            expect(router).to receive(:recognize).with(action_dispatch_request).and_return('/users/1')
-            expect(described_class.route_pattern(request)).to eq('/users/1')
+            expect(router).to receive(:recognize).with(action_dispatch_request).and_return('/users/:id(.:format)')
+            expect(described_class.route_pattern(request)).to eq('/users/:id')
           end
         end
 
@@ -143,8 +149,8 @@
           let(:request) { double('Rack::Request', env: {}, script_name: '', path: '/users/1', head?: false) }
 
           it 'uses action dispatch request for route recognition' do
-            expect(router).to receive(:recognize).with(request).and_return('/users/1')
-            expect(described_class.route_pattern(request)).to eq('/users/1')
+            expect(router).to receive(:recognize).with(request).and_return('/users/:id(.:format)')
+            expect(described_class.route_pattern(request)).to eq('/users/:id')
           end
         end
       end