Add ability to specify service names by domain

Author: stormsilver

docs/GettingStarted.md

@@ -685,6 +685,7 @@ Where `options` is an optional `Hash` that accepts the following parameters:
 | `error_handler` | A `Proc` that accepts a `response` parameter. If it evaluates to a *truthy* value, the trace span is marked as an error. By default only sets 5XX responses as errors. | `nil` |
 | `service_name` | Service name for Excon instrumentation. When provided to middleware for a specific connection, it applies only to that connection object. | `'excon'` |
 | `split_by_domain` | Uses the request domain as the service name when set to `true`. | `false` |
+| `split_by_domain_map` | When splitting by domain, provide a hash of regex => service name to override the service name for matched domains. | `{}` |
 | `tracer` | `Datadog::Tracer` used to perform instrumentation. Usually you don't need to set this. | `Datadog.tracer` |
 
 **Configuring connections to use different settings**
@@ -743,6 +744,7 @@ Where `options` is an optional `Hash` that accepts the following parameters:
 | `error_handler` | A `Proc` that accepts a `response` parameter. If it evaluates to a *truthy* value, the trace span is marked as an error. By default only sets 5XX responses as errors. | `nil` |
 | `service_name` | Service name for Faraday instrumentation. When provided to middleware for a specific connection, it applies only to that connection object. | `'faraday'` |
 | `split_by_domain` | Uses the request domain as the service name when set to `true`. | `false` |
+| `split_by_domain_map` | When splitting by domain, provide a hash of regex => service name to override the service name for matched domains. | `{}` |
 | `tracer` | `Datadog::Tracer` used to perform instrumentation. Usually, you don't need to set this. | `Datadog.tracer` |
 
 ### Grape

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

@@ -21,6 +21,7 @@ class Settings < Contrib::Configuration::Settings
           option :error_handler
           option :service_name, default: Ext::SERVICE_NAME
           option :split_by_domain, default: false
+          option :split_by_domain_map, default: {}
         end
       end
     end

lib/ddtrace/contrib/excon/middleware.rb

@@ -146,7 +146,17 @@ def propagate!(span, datum)
 
         def service_name(datum)
           # TODO: Change this to implement more sensible multiplexing
-          split_by_domain? ? datum[:host] : @options[:service_name]
+          if split_by_domain?
+            host = datum[:host]
+            @options[:split_by_domain_map].each do |matcher, service_name|
+              if matcher =~ host
+                return service_name
+              end
+            end
+            return host
+          end
+
+          @options[:service_name]
         end
       end
     end

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

@@ -26,6 +26,7 @@ class Settings < Contrib::Configuration::Settings
           option :error_handler, default: DEFAULT_ERROR_HANDLER
           option :service_name, default: Ext::SERVICE_NAME
           option :split_by_domain, default: false
+          option :split_by_domain_map, default: {}
         end
       end
     end

lib/ddtrace/contrib/faraday/middleware.rb

@@ -67,7 +67,15 @@ def tracer
         end
 
         def service_name(env)
-          return env[:url].host if options[:split_by_domain]
+          if options[:split_by_domain]
+            host = env[:url].host
+            options[:split_by_domain_map].each do |matcher, service_name|
+              if matcher =~ host
+                return service_name
+              end
+            end
+            return host
+          end
 
           options[:service_name]
         end

spec/ddtrace/contrib/excon/instrumentation_spec.rb

@@ -163,6 +163,16 @@
     end
   end
 
+  context 'when split by domain with a domain map' do
+    subject!(:response) { connection.get(path: '/success') }
+    let(:configuration_options) { super().merge(split_by_domain: true, split_by_domain_map: {/example\.com/ => 'bar'}) }
+    after(:each) { Datadog.configuration[:excon][:split_by_domain] = false; Datadog.configuration[:excon][:split_by_domain_map] = {} }
+
+    it "overrides the domain from the map" do
+      expect(request_span.service).to eq('bar')
+    end
+  end
+
   context 'default request headers' do
     subject!(:response) do
       expect_any_instance_of(Datadog::Contrib::Excon::Middleware).to receive(:request_call)

spec/ddtrace/contrib/faraday/middleware_spec.rb

@@ -140,6 +140,15 @@
     end
   end
 
+  context 'when split by domain with a domain map' do
+    subject!(:response) { client.get('/success') }
+    let(:middleware_options) { { split_by_domain: true, split_by_domain_map: {/example\.com/ => 'bar'} } }
+
+    it "overrides the domain from the map" do
+      expect(request_span.service).to eq('bar')
+    end
+  end
+
   context 'default request headers' do
     subject(:response) { client.get('/success') }