feat: Add support for upstream trace headers as request ID

cmd/proxy/actions/app.go

@@ -72,6 +72,11 @@ func App(logger *log.Logger, conf *config.Config) (http.Handler, func(), error)
 	// RegisterExporter will register an exporter where we will export our traces to.
 	// The error from the RegisterExporter would be nil if the tracer was specified by
 	// the user and the trace exporter was created successfully.
+	// RegisterPropagator installs W3C TraceContext and B3 propagation so that
+	// incoming trace headers are extracted for log correlation, regardless of
+	// whether a trace exporter is configured.
+	observ.RegisterPropagator()
+
 	// RegisterExporter returns the cleanup function that flushes remaining traces
 	// and stops the exporter. The caller is responsible for calling it at shutdown.
 	cleanupTraces := noop

go.mod

@@ -43,13 +43,13 @@ require (
 	go.etcd.io/etcd/server/v3 v3.6.10
 	go.mongodb.org/mongo-driver/v2 v2.7.0
 	go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp v0.68.0
-	go.opentelemetry.io/otel v1.43.0
+	go.opentelemetry.io/otel v1.44.0
 	go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc v1.43.0
 	go.opentelemetry.io/otel/exporters/prometheus v0.65.0
-	go.opentelemetry.io/otel/metric v1.43.0
+	go.opentelemetry.io/otel/metric v1.44.0
 	go.opentelemetry.io/otel/sdk v1.43.0
 	go.opentelemetry.io/otel/sdk/metric v1.43.0
-	go.opentelemetry.io/otel/trace v1.43.0
+	go.opentelemetry.io/otel/trace v1.44.0
 	golang.org/x/mod v0.35.0
 	golang.org/x/oauth2 v0.36.0
 	golang.org/x/sync v0.21.0
@@ -158,6 +158,7 @@ require (
 	go.opentelemetry.io/auto/sdk v1.2.1 // indirect
 	go.opentelemetry.io/contrib/detectors/gcp v1.43.0 // indirect
 	go.opentelemetry.io/contrib/instrumentation/google.golang.org/grpc/otelgrpc v0.68.0 // indirect
+	go.opentelemetry.io/contrib/propagators/b3 v1.44.0 // indirect
 	go.opentelemetry.io/otel/exporters/otlp/otlptrace v1.43.0 // indirect
 	go.opentelemetry.io/proto/otlp v1.10.0 // indirect
 	go.uber.org/atomic v1.11.0 // indirect

go.sum

@@ -398,8 +398,12 @@ go.opentelemetry.io/contrib/instrumentation/google.golang.org/grpc/otelgrpc v0.6
 go.opentelemetry.io/contrib/instrumentation/google.golang.org/grpc/otelgrpc v0.68.0/go.mod h1:Sje3i3MjSPKTSPvVWCaL8ugBzJwik3u4smCjUeuupqg=
 go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp v0.68.0 h1:CqXxU8VOmDefoh0+ztfGaymYbhdB/tT3zs79QaZTNGY=
 go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp v0.68.0/go.mod h1:BuhAPThV8PBHBvg8ZzZ/Ok3idOdhWIodywz2xEcRbJo=
+go.opentelemetry.io/contrib/propagators/b3 v1.44.0 h1:1IFH4oFKK8KupzIelCl3u+bkxpGRps1oWRjQI2+TTWs=
+go.opentelemetry.io/contrib/propagators/b3 v1.44.0/go.mod h1:JqWFXsc7VDaqIyubFhEd2cPHqsrzqP0Lvn783SUwyro=
 go.opentelemetry.io/otel v1.43.0 h1:mYIM03dnh5zfN7HautFE4ieIig9amkNANT+xcVxAj9I=
 go.opentelemetry.io/otel v1.43.0/go.mod h1:JuG+u74mvjvcm8vj8pI5XiHy1zDeoCS2LB1spIq7Ay0=
+go.opentelemetry.io/otel v1.44.0 h1:JjwHmHpA4iZ3wBxluu2fbbE7j4kqlE8jXyAyPXH7HqU=
+go.opentelemetry.io/otel v1.44.0/go.mod h1:BMgjTHL9WPRlRjL2oZCBTL4whCGtXch2H4BhOPIAyYc=
 go.opentelemetry.io/otel/exporters/otlp/otlptrace v1.43.0 h1:88Y4s2C8oTui1LGM6bTWkw0ICGcOLCAI5l6zsD1j20k=
 go.opentelemetry.io/otel/exporters/otlp/otlptrace v1.43.0/go.mod h1:Vl1/iaggsuRlrHf/hfPJPvVag77kKyvrLeD10kpMl+A=
 go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc v1.43.0 h1:RAE+JPfvEmvy+0LzyUA25/SGawPwIUbZ6u0Wug54sLc=
@@ -410,12 +414,16 @@ go.opentelemetry.io/otel/exporters/stdout/stdoutmetric v1.43.0 h1:TC+BewnDpeiAmc
 go.opentelemetry.io/otel/exporters/stdout/stdoutmetric v1.43.0/go.mod h1:J/ZyF4vfPwsSr9xJSPyQ4LqtcTPULFR64KwTikGLe+A=
 go.opentelemetry.io/otel/metric v1.43.0 h1:d7638QeInOnuwOONPp4JAOGfbCEpYb+K6DVWvdxGzgM=
 go.opentelemetry.io/otel/metric v1.43.0/go.mod h1:RDnPtIxvqlgO8GRW18W6Z/4P462ldprJtfxHxyKd2PY=
+go.opentelemetry.io/otel/metric v1.44.0 h1:1w0gILTcHdr3YI+ixLyjemwrVnsMURbTZFrSYCdDdmc=
+go.opentelemetry.io/otel/metric v1.44.0/go.mod h1:8O7hanEPBNgEMmybD3s2VBKcgWOCsA6tzHBPODAiquo=
 go.opentelemetry.io/otel/sdk v1.43.0 h1:pi5mE86i5rTeLXqoF/hhiBtUNcrAGHLKQdhg4h4V9Dg=
 go.opentelemetry.io/otel/sdk v1.43.0/go.mod h1:P+IkVU3iWukmiit/Yf9AWvpyRDlUeBaRg6Y+C58QHzg=
 go.opentelemetry.io/otel/sdk/metric v1.43.0 h1:S88dyqXjJkuBNLeMcVPRFXpRw2fuwdvfCGLEo89fDkw=
 go.opentelemetry.io/otel/sdk/metric v1.43.0/go.mod h1:C/RJtwSEJ5hzTiUz5pXF1kILHStzb9zFlIEe85bhj6A=
 go.opentelemetry.io/otel/trace v1.43.0 h1:BkNrHpup+4k4w+ZZ86CZoHHEkohws8AY+WTX09nk+3A=
 go.opentelemetry.io/otel/trace v1.43.0/go.mod h1:/QJhyVBUUswCphDVxq+8mld+AvhXZLhe+8WVFxiFff0=
+go.opentelemetry.io/otel/trace v1.44.0 h1:jxF5CsGYCe74MCRx2X4g7WsY/VBKRqqpNvXlX/6gtIk=
+go.opentelemetry.io/otel/trace v1.44.0/go.mod h1:oLl1jrMQAVo6v3GAggN+1VH9VIz9iUSvW53sW1Q8PIE=
 go.opentelemetry.io/proto/otlp v1.10.0 h1:IQRWgT5srOCYfiWnpqUYz9CVmbO8bFmKcwYxpuCSL2g=
 go.opentelemetry.io/proto/otlp v1.10.0/go.mod h1:/CV4QoCR/S9yaPj8utp3lvQPoqMtxXdzn7ozvvozVqk=
 go.uber.org/atomic v1.11.0 h1:ZvwS0R+56ePWxUNi+Atn9dWONBPp/AUETXlHW0DxSjE=

pkg/middleware/requestid.go

@@ -1,23 +1,40 @@
 package middleware
 
 import (
+	"context"
 	"net/http"
 
 	"github.com/gomods/athens/pkg/requestid"
 	"github.com/google/uuid"
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/propagation"
+	"go.opentelemetry.io/otel/trace"
 )
 
-// WithRequestID ensures a request id is in the
-// request context by either the incoming header
-// or creating a new one.
+// WithRequestID ensures a request id is in the request context.
+// It prefers the trace ID extracted from incoming trace headers
+// (traceparent/b3) via the global OTel propagator, then falls back
+// to the Athens-Request-ID header, and finally generates a UUID.
 func WithRequestID(h http.Handler) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		requestID := r.Header.Get(requestid.HeaderKey)
-		if requestID == "" {
+		var requestID string
+		if sc := extractRemoteSpanContext(r.Context(), r.Header); sc.HasTraceID() {
+			requestID = sc.TraceID().String()
+		} else if id := r.Header.Get(requestid.HeaderKey); id != "" {
+			requestID = id
+		} else {
 			requestID = uuid.New().String()
 		}
 		ctx := requestid.SetInContext(r.Context(), requestID)
 		r = r.WithContext(ctx)
 		h.ServeHTTP(w, r)
 	})
 }
+
+// extractRemoteSpanContext uses the global OTel propagator to extract
+// a span context from the request headers. Returns an empty SpanContext
+// if no valid trace headers are present.
+func extractRemoteSpanContext(ctx context.Context, headers http.Header) trace.SpanContext {
+	ctx = otel.GetTextMapPropagator().Extract(ctx, propagation.HeaderCarrier(headers))
+	return trace.SpanContextFromContext(ctx)
+}

pkg/middleware/requestid_test.go

@@ -7,25 +7,123 @@ import (
 
 	"github.com/gomods/athens/pkg/requestid"
 	"github.com/google/uuid"
+	"go.opentelemetry.io/contrib/propagators/b3"
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/propagation"
 )
 
+func init() {
+	// Set up composite propagator for tests (same as production).
+	otel.SetTextMapPropagator(propagation.NewCompositeTextMapPropagator(
+		b3.New(),
+		propagation.TraceContext{},
+		propagation.Baggage{},
+	))
+}
+
 func TestWithRequestID(t *testing.T) {
 	var givenRequestID string
-	h := WithRequestID(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+	handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		givenRequestID = requestid.FromContext(r.Context())
-	}))
-	req := httptest.NewRequest("GET", "/", nil)
-	expectedRequestID := uuid.New().String()
-	req.Header.Set(requestid.HeaderKey, expectedRequestID)
-	w := httptest.NewRecorder()
-	h.ServeHTTP(w, req)
-	if givenRequestID != expectedRequestID {
-		t.Fatalf("expected request id to be %q but got %q", expectedRequestID, givenRequestID)
-	}
-	req = httptest.NewRequest("GET", "/", nil)
-	w = httptest.NewRecorder()
-	h.ServeHTTP(w, req)
-	if givenRequestID == "" {
-		t.Fatal("expected a request id to be created when a request id header is empty")
-	}
+	})
+
+	t.Run("uses trace ID from W3C traceparent header", func(t *testing.T) {
+		h := WithRequestID(handler)
+		req := httptest.NewRequest("GET", "/", nil)
+		req.Header.Set("Traceparent", "00-4bf92f3577b6a814af67ab2d6fc0f4e1-00f067aa0ba902b7-01")
+		w := httptest.NewRecorder()
+		h.ServeHTTP(w, req)
+		if givenRequestID != "4bf92f3577b6a814af67ab2d6fc0f4e1" {
+			t.Fatalf("expected trace id %q but got %q", "4bf92f3577b6a814af67ab2d6fc0f4e1", givenRequestID)
+		}
+	})
+
+	t.Run("uses trace ID from B3 multi-header", func(t *testing.T) {
+		h := WithRequestID(handler)
+		req := httptest.NewRequest("GET", "/", nil)
+		req.Header.Set("X-B3-TraceId", "463ac35c9f6413ad48485a3953bb6124")
+		req.Header.Set("X-B3-SpanId", "0020000000000001")
+		req.Header.Set("X-B3-Sampled", "1")
+		w := httptest.NewRecorder()
+		h.ServeHTTP(w, req)
+		if givenRequestID != "463ac35c9f6413ad48485a3953bb6124" {
+			t.Fatalf("expected trace id %q but got %q", "463ac35c9f6413ad48485a3953bb6124", givenRequestID)
+		}
+	})
+
+	t.Run("uses trace ID from B3 single header", func(t *testing.T) {
+		h := WithRequestID(handler)
+		req := httptest.NewRequest("GET", "/", nil)
+		req.Header.Set("B3", "80f198ee56343ba864fe8b2a57d3eff7-e457b5a2e4d86bd1-1")
+		w := httptest.NewRecorder()
+		h.ServeHTTP(w, req)
+		if givenRequestID != "80f198ee56343ba864fe8b2a57d3eff7" {
+			t.Fatalf("expected trace id %q but got %q", "80f198ee56343ba864fe8b2a57d3eff7", givenRequestID)
+		}
+	})
+
+	t.Run("W3C takes priority over B3 when both present", func(t *testing.T) {
+		h := WithRequestID(handler)
+		req := httptest.NewRequest("GET", "/", nil)
+		req.Header.Set("Traceparent", "00-aaaa1111bbbb2222cccc3333dddd4444-00f067aa0ba902b7-01")
+		req.Header.Set("X-B3-TraceId", "1111222233334444aaaabbbbccccdddd")
+		req.Header.Set("X-B3-SpanId", "0020000000000001")
+		req.Header.Set("X-B3-Sampled", "1")
+		w := httptest.NewRecorder()
+		h.ServeHTTP(w, req)
+		if givenRequestID != "aaaa1111bbbb2222cccc3333dddd4444" {
+			t.Fatalf("expected W3C trace id %q to win but got %q", "aaaa1111bbbb2222cccc3333dddd4444", givenRequestID)
+		}
+	})
+
+	t.Run("falls back to Athens-Request-ID header when no trace headers", func(t *testing.T) {
+		h := WithRequestID(handler)
+		req := httptest.NewRequest("GET", "/", nil)
+		req.Header.Set(requestid.HeaderKey, "my-custom-id-123")
+		w := httptest.NewRecorder()
+		h.ServeHTTP(w, req)
+		if givenRequestID != "my-custom-id-123" {
+			t.Fatalf("expected %q but got %q", "my-custom-id-123", givenRequestID)
+		}
+	})
+
+	t.Run("generates UUID when no trace headers and no Athens header", func(t *testing.T) {
+		h := WithRequestID(handler)
+		req := httptest.NewRequest("GET", "/", nil)
+		w := httptest.NewRecorder()
+		h.ServeHTTP(w, req)
+		if givenRequestID == "" {
+			t.Fatal("expected a request id to be generated")
+		}
+		if _, err := uuid.Parse(givenRequestID); err != nil {
+			t.Fatalf("expected a valid UUID but got %q: %v", givenRequestID, err)
+		}
+	})
+
+	t.Run("falls back to UUID on malformed traceparent", func(t *testing.T) {
+		h := WithRequestID(handler)
+		req := httptest.NewRequest("GET", "/", nil)
+		req.Header.Set("Traceparent", "invalid-traceparent-value")
+		w := httptest.NewRecorder()
+		h.ServeHTTP(w, req)
+		if givenRequestID == "" {
+			t.Fatal("expected a request id to be generated")
+		}
+		if _, err := uuid.Parse(givenRequestID); err != nil {
+			t.Fatalf("expected a valid UUID but got %q: %v", givenRequestID, err)
+		}
+	})
+
+	t.Run("falls back to Athens-Request-ID on malformed B3 header", func(t *testing.T) {
+		h := WithRequestID(handler)
+		req := httptest.NewRequest("GET", "/", nil)
+		req.Header.Set("X-B3-TraceId", "not-a-valid-hex-id")
+		req.Header.Set("X-B3-SpanId", "also-invalid")
+		req.Header.Set(requestid.HeaderKey, "fallback-id")
+		w := httptest.NewRecorder()
+		h.ServeHTTP(w, req)
+		if givenRequestID != "fallback-id" {
+			t.Fatalf("expected fallback %q but got %q", "fallback-id", givenRequestID)
+		}
+	})
 }

pkg/observ/observ.go

@@ -6,6 +6,7 @@ import (
 	"time"
 
 	"github.com/gomods/athens/pkg/errors"
+	"go.opentelemetry.io/contrib/propagators/b3"
 	"go.opentelemetry.io/otel"
 	"go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc"
 	"go.opentelemetry.io/otel/propagation"
@@ -21,6 +22,18 @@ const instrumentationName = "github.com/gomods/athens"
 // shutdownTimeout bounds how long provider shutdown may block while flushing.
 const shutdownTimeout = 5 * time.Second
 
+// RegisterPropagator installs the global OTel text map propagator with support
+// for W3C TraceContext and Zipkin B3 (single + multiple header). This is
+// registered unconditionally so that trace context can be extracted for log
+// correlation even when no trace exporter is configured.
+func RegisterPropagator() {
+	otel.SetTextMapPropagator(propagation.NewCompositeTextMapPropagator(
+		b3.New(),
+		propagation.TraceContext{},
+		propagation.Baggage{},
+	))
+}
+
 // RegisterExporter configures the OpenTelemetry TracerProvider used to export traces.
 //
 // Athens exports traces via OTLP. The traceExporter argument acts as a toggle:
@@ -79,10 +92,6 @@ func registerOTLPExporter(url, service, env string, samplingFraction float64) (f
 		sdktrace.WithSampler(sampler),
 	)
 	otel.SetTracerProvider(tp)
-	otel.SetTextMapPropagator(propagation.NewCompositeTextMapPropagator(
-		propagation.TraceContext{},
-		propagation.Baggage{},
-	))
 
 	return func() {
 		ctx, cancel := context.WithTimeout(context.Background(), shutdownTimeout)