[core] Propagate synthetics origin headers (#699)

* [core] Inject/extract synthetics origin header

* only set origin header if non-nil

* fix opentracing specs

* inject/extract origin for gRPC

* move origin test to context_spec.rb

* move distributed headers origin test to RSpec

* fix linting issues

* use subject for origin test case

lib/ddtrace/context.rb

@@ -53,6 +53,18 @@ def sampling_priority=(priority)
       end
     end
 
+    def origin
+      @mutex.synchronize do
+        @origin
+      end
+    end
+
+    def origin=(origin)
+      @mutex.synchronize do
+        @origin = origin
+      end
+    end
+
     # Return the last active span that corresponds to the last inserted
     # item in the trace list. This cannot be considered as the current active
     # span in asynchronous environments, because some spans can be closed
@@ -138,6 +150,7 @@ def get
         sampled = @sampled
 
         attach_sampling_priority if sampled && @sampling_priority
+        attach_origin if @origin
 
         # still return sampled attribute, even if context is not finished
         return nil, sampled unless check_finished_spans()
@@ -163,6 +176,7 @@ def reset(options = {})
       @parent_span_id = options.fetch(:span_id, nil)
       @sampled = options.fetch(:sampled, false)
       @sampling_priority = options.fetch(:sampling_priority, nil)
+      @origin = options.fetch(:origin, nil)
       @finished_spans = 0
       @current_span = nil
       @current_root_span = nil
@@ -192,6 +206,13 @@ def attach_sampling_priority
       )
     end
 
+    def attach_origin
+      @trace.first.set_tag(
+        Ext::DistributedTracing::ORIGIN_KEY,
+        @origin
+      )
+    end
+
     # Return the start time of the root span, or nil if there are no spans or this is undefined.
     def start_time
       @mutex.synchronize do

lib/ddtrace/ext/distributed.rb

@@ -7,11 +7,14 @@ module DistributedTracing
       HTTP_HEADER_PARENT_ID = 'x-datadog-parent-id'.freeze
       HTTP_HEADER_SAMPLING_PRIORITY = 'x-datadog-sampling-priority'.freeze
       SAMPLING_PRIORITY_KEY = '_sampling_priority_v1'.freeze
+      HTTP_HEADER_ORIGIN = 'x-datadog-origin'.freeze
+      ORIGIN_KEY = '_dd.origin'.freeze
 
       # gRPC metadata keys for distributed tracing. https://github.com/grpc/grpc-go/blob/v1.10.x/Documentation/grpc-metadata.md
       GRPC_METADATA_TRACE_ID = 'x-datadog-trace-id'.freeze
       GRPC_METADATA_PARENT_ID = 'x-datadog-parent-id'.freeze
       GRPC_METADATA_SAMPLING_PRIORITY = 'x-datadog-sampling-priority'.freeze
+      GRPC_METADATA_ORIGIN = 'x-datadog-origin'.freeze
     end
   end
 end

lib/ddtrace/opentracer/distributed_headers.rb

@@ -34,6 +34,12 @@ def sampling_priority
         value
       end
 
+      def origin
+        hdr = @carrier[HTTP_HEADER_ORIGIN]
+        # Only return the value if it is not an empty string
+        hdr if hdr != ''
+      end
+
       private
 
       def id(header)

lib/ddtrace/opentracer/text_map_propagator.rb

@@ -21,6 +21,7 @@ def inject(span_context, carrier)
             carrier[HTTP_HEADER_TRACE_ID] = datadog_context.trace_id
             carrier[HTTP_HEADER_PARENT_ID] = datadog_context.span_id
             carrier[HTTP_HEADER_SAMPLING_PRIORITY] = datadog_context.sampling_priority
+            carrier[HTTP_HEADER_ORIGIN] = datadog_context.origin
           end
 
           # Inject baggage
@@ -43,7 +44,8 @@ def extract(carrier)
                               Datadog::Context.new(
                                 trace_id: headers.trace_id,
                                 span_id: headers.parent_id,
-                                sampling_priority: headers.sampling_priority
+                                sampling_priority: headers.sampling_priority,
+                                origin: headers.origin
                               )
                             else
                               Datadog::Context.new

lib/ddtrace/propagation/distributed_headers.rb

@@ -11,7 +11,7 @@ def initialize(env)
     end
 
     def valid?
-      # Sampling priority is optional.
+      # Sampling priority and origin are optional.
       trace_id && parent_id
     end
 
@@ -33,6 +33,12 @@ def sampling_priority
       value
     end
 
+    def origin
+      hdr = header(HTTP_HEADER_ORIGIN)
+      # Only return the value if it is not an empty string
+      hdr if hdr != ''
+    end
+
     private
 
     def header(name)

lib/ddtrace/propagation/grpc_propagator.rb

@@ -13,14 +13,16 @@ def self.inject!(context, metadata)
       metadata[GRPC_METADATA_TRACE_ID] = context.trace_id.to_s
       metadata[GRPC_METADATA_PARENT_ID] = context.span_id.to_s
       metadata[GRPC_METADATA_SAMPLING_PRIORITY] = context.sampling_priority.to_s if context.sampling_priority
+      metadata[GRPC_METADATA_ORIGIN] = context.origin.to_s if context.origin
     end
 
     def self.extract(metadata)
       metadata = Carrier.new(metadata)
       return Datadog::Context.new unless metadata.valid?
       Datadog::Context.new(trace_id: metadata.trace_id,
                            span_id: metadata.parent_id,
-                           sampling_priority: metadata.sampling_priority)
+                           sampling_priority: metadata.sampling_priority,
+                           origin: metadata.origin)
     end
 
     # opentracing.io compliant carrier object
@@ -49,6 +51,11 @@ def sampling_priority
         value = @metadata[GRPC_METADATA_SAMPLING_PRIORITY]
         value && value.to_i
       end
+
+      def origin
+        value = @metadata[GRPC_METADATA_ORIGIN]
+        value if value != ''
+      end
     end
   end
 end

lib/ddtrace/propagation/http_propagator.rb

@@ -18,6 +18,7 @@ def self.inject!(context, env)
       env[HTTP_HEADER_TRACE_ID] = context.trace_id.to_s
       env[HTTP_HEADER_PARENT_ID] = context.span_id.to_s
       env[HTTP_HEADER_SAMPLING_PRIORITY] = context.sampling_priority.to_s
+      env[HTTP_HEADER_ORIGIN] = context.origin.to_s if context.origin
       env.delete(HTTP_HEADER_SAMPLING_PRIORITY) unless context.sampling_priority
     end
 
@@ -28,7 +29,8 @@ def self.extract(env)
       return Datadog::Context.new unless headers.valid?
       Datadog::Context.new(trace_id: headers.trace_id,
                            span_id: headers.parent_id,
-                           sampling_priority: headers.sampling_priority)
+                           sampling_priority: headers.sampling_priority,
+                           origin: headers.origin)
     end
   end
 end

spec/ddtrace/context_spec.rb

@@ -43,4 +43,22 @@
       end
     end
   end
+
+  describe '#origin' do
+    context 'with nil' do
+      before(:each) { context.origin = nil }
+      it { expect(context.origin).to be_nil }
+    end
+
+    context 'with empty string' do
+      # We do not do any filtering based on value
+      before(:each) { context.origin = '' }
+      it { expect(context.origin).to eq('') }
+    end
+
+    context 'with synthetics' do
+      before(:each) { context.origin = 'synthetics' }
+      it { expect(context.origin).to eq('synthetics') }
+    end
+  end
 end

spec/ddtrace/contrib/rack/distributed_spec.rb

@@ -40,18 +40,21 @@
     let(:trace_id) { 8694058539399423136 }
     let(:parent_id) { 3605612475141592985 }
     let(:sampling_priority) { Datadog::Ext::Priority::AUTO_KEEP }
+    let(:origin) { 'synthetics' }
 
     before(:each) do
       header Datadog::Ext::DistributedTracing::HTTP_HEADER_TRACE_ID, trace_id
       header Datadog::Ext::DistributedTracing::HTTP_HEADER_PARENT_ID, parent_id
       header Datadog::Ext::DistributedTracing::HTTP_HEADER_SAMPLING_PRIORITY, sampling_priority
+      header Datadog::Ext::DistributedTracing::HTTP_HEADER_ORIGIN, origin
     end
   end
 
   shared_context 'no distributed tracing headers' do
     let(:trace_id) { nil }
     let(:parent_id) { nil }
     let(:sampling_priority) { nil }
+    let(:origin) { nil }
   end
 
   shared_examples_for 'a Rack request with distributed tracing' do
@@ -62,6 +65,7 @@
       expect(span.trace_id).to eq(trace_id)
       expect(span.parent_id).to eq(parent_id)
       expect(span.get_metric(Datadog::Ext::DistributedTracing::SAMPLING_PRIORITY_KEY)).to eq(sampling_priority)
+      expect(span.get_tag(Datadog::Ext::DistributedTracing::ORIGIN_KEY)).to eq(origin)
     end
   end
 
@@ -73,6 +77,7 @@
       expect(span.trace_id).to_not eq(trace_id)
       expect(span.parent_id).to eq(0)
       expect(span.get_metric(Datadog::Ext::DistributedTracing::SAMPLING_PRIORITY_KEY)).to be nil
+      expect(span.get_tag(Datadog::Ext::DistributedTracing::ORIGIN_KEY)).to be nil
     end
   end
 

spec/ddtrace/contrib/sinatra/tracer_spec.rb

@@ -309,7 +309,8 @@
             {
               'HTTP_X_DATADOG_TRACE_ID' => '1',
               'HTTP_X_DATADOG_PARENT_ID' => '2',
-              'HTTP_X_DATADOG_SAMPLING_PRIORITY' => Datadog::Ext::Priority::USER_KEEP.to_s
+              'HTTP_X_DATADOG_SAMPLING_PRIORITY' => Datadog::Ext::Priority::USER_KEEP.to_s,
+              'HTTP_X_DATADOG_ORIGIN' => 'synthetics'
             }
           end
 
@@ -319,6 +320,7 @@
             expect(span.trace_id).to eq(1)
             expect(span.parent_id).to eq(2)
             expect(span.get_metric(Datadog::Ext::DistributedTracing::SAMPLING_PRIORITY_KEY)).to eq(2.0)
+            expect(span.get_tag(Datadog::Ext::DistributedTracing::ORIGIN_KEY)).to eq('synthetics')
           end
         end
       end

spec/ddtrace/integration_spec.rb

@@ -175,6 +175,26 @@ def agent_receives_span_step3(previous_success)
     end
   end
 
+  describe 'origin tag' do
+    # Sampling priority is enabled by default
+    let(:tracer) { get_test_tracer }
+
+    context 'when #sampling_priority is set on a parent span' do
+      subject(:tag_value) { parent_span.get_tag(Datadog::Ext::DistributedTracing::ORIGIN_KEY) }
+      let(:parent_span) { tracer.start_span('parent span') }
+
+      before(:each) do
+        parent_span.tap do
+          parent_span.context.origin = 'synthetics'
+        end.finish
+
+        try_wait_until { tracer.writer.spans(:keep).any? }
+      end
+
+      it { is_expected.to eq('synthetics') }
+    end
+  end
+
   describe 'sampling priority integration' do
     include_context 'agent-based test'
 

spec/ddtrace/opentracer/propagation_integration_spec.rb

@@ -15,6 +15,10 @@ def sampling_priority_metric(span)
       span.get_metric(Datadog::OpenTracer::TextMapPropagator::SAMPLING_PRIORITY_KEY)
     end
 
+    def origin_tag(span)
+      span.get_tag(Datadog::OpenTracer::TextMapPropagator::ORIGIN_KEY)
+    end
+
     describe 'via OpenTracing::FORMAT_TEXT_MAP' do
       def baggage_to_carrier_format(baggage)
         baggage.map { |k, v| [Datadog::OpenTracer::TextMapPropagator::BAGGAGE_PREFIX + k, v] }.to_h
@@ -28,6 +32,7 @@ def baggage_to_carrier_format(baggage)
         before(:each) do
           tracer.start_active_span(span_name) do |scope|
             scope.span.context.datadog_context.sampling_priority = 1
+            scope.span.context.datadog_context.origin = 'synthetics'
             baggage.each { |k, v| scope.span.set_baggage_item(k, v) }
             tracer.inject(
               scope.span.context,
@@ -41,7 +46,8 @@ def baggage_to_carrier_format(baggage)
           expect(carrier).to include(
             Datadog::OpenTracer::TextMapPropagator::HTTP_HEADER_TRACE_ID => a_kind_of(Integer),
             Datadog::OpenTracer::TextMapPropagator::HTTP_HEADER_PARENT_ID => a_kind_of(Integer),
-            Datadog::OpenTracer::TextMapPropagator::HTTP_HEADER_SAMPLING_PRIORITY => a_kind_of(Integer)
+            Datadog::OpenTracer::TextMapPropagator::HTTP_HEADER_SAMPLING_PRIORITY => a_kind_of(Integer),
+            Datadog::OpenTracer::TextMapPropagator::HTTP_HEADER_ORIGIN => a_kind_of(String)
           )
 
           expect(carrier[Datadog::OpenTracer::TextMapPropagator::HTTP_HEADER_PARENT_ID]).to be > 0
@@ -71,13 +77,15 @@ def baggage_to_carrier_format(baggage)
             super().merge(
               Datadog::OpenTracer::TextMapPropagator::HTTP_HEADER_TRACE_ID => trace_id.to_s,
               Datadog::OpenTracer::TextMapPropagator::HTTP_HEADER_PARENT_ID => parent_id.to_s,
-              Datadog::OpenTracer::TextMapPropagator::HTTP_HEADER_SAMPLING_PRIORITY => sampling_priority.to_s
+              Datadog::OpenTracer::TextMapPropagator::HTTP_HEADER_SAMPLING_PRIORITY => sampling_priority.to_s,
+              Datadog::OpenTracer::TextMapPropagator::HTTP_HEADER_ORIGIN => origin.to_s
             )
           end
 
           let(:trace_id) { Datadog::Span::MAX_ID - 1 }
           let(:parent_id) { Datadog::Span::MAX_ID - 2 }
           let(:sampling_priority) { 2 }
+          let(:origin) { 'synthetics' }
 
           let(:datadog_span) { datadog_spans.first }
 
@@ -87,6 +95,7 @@ def baggage_to_carrier_format(baggage)
           it { expect(datadog_span.trace_id).to eq(trace_id) }
           it { expect(datadog_span.parent_id).to eq(parent_id) }
           it { expect(sampling_priority_metric(datadog_span)).to eq(sampling_priority) }
+          it { expect(origin_tag(datadog_span)).to eq(origin) }
           it { expect(@scope.span.context.baggage).to include(baggage) }
         end
 
@@ -111,6 +120,7 @@ def baggage_to_carrier_format(baggage)
         before(:each) do
           tracer.start_active_span(sender_span_name) do |sender_scope|
             sender_scope.span.context.datadog_context.sampling_priority = 1
+            sender_scope.span.context.datadog_context.origin = 'synthetics'
             baggage.each { |k, v| sender_scope.span.set_baggage_item(k, v) }
             tracer.inject(
               sender_scope.span.context,
@@ -134,11 +144,13 @@ def baggage_to_carrier_format(baggage)
         it { expect(sender_datadog_span.finished?).to be(true) }
         it { expect(sender_datadog_span.parent_id).to eq(0) }
         it { expect(sampling_priority_metric(sender_datadog_span)).to eq(1) }
+        it { expect(origin_tag(sender_datadog_span)).to eq('synthetics') }
         it { expect(receiver_datadog_span.name).to eq(receiver_span_name) }
         it { expect(receiver_datadog_span.finished?).to be(true) }
         it { expect(receiver_datadog_span.trace_id).to eq(sender_datadog_span.trace_id) }
         it { expect(receiver_datadog_span.parent_id).to eq(sender_datadog_span.span_id) }
         it { expect(sampling_priority_metric(receiver_datadog_span)).to eq(1) }
+        it { expect(origin_tag(receiver_datadog_span)).to eq('synthetics') }
         it { expect(@receiver_scope.span.context.baggage).to include(baggage) }
       end
     end
@@ -160,6 +172,7 @@ def baggage_to_carrier_format(baggage)
         before(:each) do
           tracer.start_active_span(span_name) do |scope|
             scope.span.context.datadog_context.sampling_priority = 1
+            scope.span.context.datadog_context.origin = 'synthetics'
             baggage.each { |k, v| scope.span.set_baggage_item(k, v) }
             tracer.inject(
               scope.span.context,
@@ -173,7 +186,8 @@ def baggage_to_carrier_format(baggage)
           expect(carrier).to include(
             Datadog::OpenTracer::RackPropagator::HTTP_HEADER_TRACE_ID => a_kind_of(String),
             Datadog::OpenTracer::RackPropagator::HTTP_HEADER_PARENT_ID => a_kind_of(String),
-            Datadog::OpenTracer::RackPropagator::HTTP_HEADER_SAMPLING_PRIORITY => a_kind_of(String)
+            Datadog::OpenTracer::RackPropagator::HTTP_HEADER_SAMPLING_PRIORITY => a_kind_of(String),
+            Datadog::OpenTracer::RackPropagator::HTTP_HEADER_ORIGIN => a_kind_of(String)
           )
 
           expect(carrier[Datadog::OpenTracer::RackPropagator::HTTP_HEADER_PARENT_ID].to_i).to be > 0
@@ -204,14 +218,16 @@ def baggage_to_carrier_format(baggage)
               carrier_to_rack_format(
                 Datadog::OpenTracer::RackPropagator::HTTP_HEADER_TRACE_ID => trace_id.to_s,
                 Datadog::OpenTracer::RackPropagator::HTTP_HEADER_PARENT_ID => parent_id.to_s,
-                Datadog::OpenTracer::RackPropagator::HTTP_HEADER_SAMPLING_PRIORITY => sampling_priority.to_s
+                Datadog::OpenTracer::RackPropagator::HTTP_HEADER_SAMPLING_PRIORITY => sampling_priority.to_s,
+                Datadog::OpenTracer::RackPropagator::HTTP_HEADER_ORIGIN => origin.to_s
               )
             )
           end
 
           let(:trace_id) { Datadog::Span::MAX_ID - 1 }
           let(:parent_id) { Datadog::Span::MAX_ID - 2 }
           let(:sampling_priority) { 2 }
+          let(:origin) { 'synthetics' }
 
           let(:datadog_span) { datadog_spans.first }
 
@@ -221,6 +237,7 @@ def baggage_to_carrier_format(baggage)
           it { expect(datadog_span.trace_id).to eq(trace_id) }
           it { expect(datadog_span.parent_id).to eq(parent_id) }
           it { expect(sampling_priority_metric(datadog_span)).to eq(sampling_priority) }
+          it { expect(origin_tag(datadog_span)).to eq('synthetics') }
           it { expect(@scope.span.context.baggage).to include(baggage) }
         end
 
@@ -249,6 +266,7 @@ def baggage_to_carrier_format(baggage)
         before(:each) do
           tracer.start_active_span(sender_span_name) do |sender_scope|
             sender_scope.span.context.datadog_context.sampling_priority = 1
+            sender_scope.span.context.datadog_context.origin = 'synthetics'
             baggage.each { |k, v| sender_scope.span.set_baggage_item(k, v) }
 
             carrier = {}