snapshot of https://github.com/grpc/grpc-go.git (master, 2026-09-15; blobs > 131072B omitted)

stats/opentelemetry/grpc_trace_bin_propagator.go

@@ -0,0 +1,119 @@
+/*
+ *
+ * Copyright 2024 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package opentelemetry
+
+import (
+	"context"
+
+	otelpropagation "go.opentelemetry.io/otel/propagation"
+	oteltrace "go.opentelemetry.io/otel/trace"
+)
+
+// gRPCTraceBinHeaderKey is the gRPC metadata header key `grpc-trace-bin` used
+// to propagate trace context in binary format.
+const grpcTraceBinHeaderKey = "grpc-trace-bin"
+
+// GRPCTraceBinPropagator is an OpenTelemetry TextMapPropagator which is used
+// to extract and inject trace context data from and into headers exchanged by
+// gRPC applications. It propagates trace data in binary format using the
+// `grpc-trace-bin` header.
+type GRPCTraceBinPropagator struct{}
+
+// Inject sets OpenTelemetry span context from the Context into the carrier as
+// a `grpc-trace-bin` header if span context is valid.
+//
+// If span context is not valid, it returns without setting `grpc-trace-bin`
+// header.
+func (GRPCTraceBinPropagator) Inject(ctx context.Context, carrier otelpropagation.TextMapCarrier) {
+	sc := oteltrace.SpanFromContext(ctx)
+	if !sc.SpanContext().IsValid() {
+		return
+	}
+
+	bd := toBinary(sc.SpanContext())
+	carrier.Set(grpcTraceBinHeaderKey, string(bd))
+}
+
+// Extract reads OpenTelemetry span context from the `grpc-trace-bin` header of
+// carrier into the provided context, if present.
+//
+// If a valid span context is retrieved from `grpc-trace-bin`, it returns a new
+// context containing the extracted OpenTelemetry span context marked as
+// remote.
+//
+// If `grpc-trace-bin` header is not present, it returns the context as is.
+func (GRPCTraceBinPropagator) Extract(ctx context.Context, carrier otelpropagation.TextMapCarrier) context.Context {
+	h := carrier.Get(grpcTraceBinHeaderKey)
+	if h == "" {
+		return ctx
+	}
+
+	sc, ok := fromBinary([]byte(h))
+	if !ok {
+		return ctx
+	}
+	return oteltrace.ContextWithRemoteSpanContext(ctx, sc)
+}
+
+// Fields returns the keys whose values are set with Inject.
+//
+// GRPCTraceBinPropagator always returns a slice containing only
+// `grpc-trace-bin` key because it only sets the `grpc-trace-bin` header for
+// propagating trace context.
+func (GRPCTraceBinPropagator) Fields() []string {
+	return []string{grpcTraceBinHeaderKey}
+}
+
+// toBinary returns the binary format representation of a SpanContext.
+//
+// If sc is the zero value, returns nil.
+func toBinary(sc oteltrace.SpanContext) []byte {
+	if sc.Equal(oteltrace.SpanContext{}) {
+		return nil
+	}
+	var b [29]byte
+	traceID := oteltrace.TraceID(sc.TraceID())
+	copy(b[2:18], traceID[:])
+	b[18] = 1
+	spanID := oteltrace.SpanID(sc.SpanID())
+	copy(b[19:27], spanID[:])
+	b[27] = 2
+	b[28] = byte(oteltrace.TraceFlags(sc.TraceFlags()))
+	return b[:]
+}
+
+// fromBinary returns the SpanContext represented by b with Remote set to true.
+//
+// It returns with zero value SpanContext and false, if any of the
+// below condition is not satisfied:
+// - Valid header: len(b) = 29
+// - Valid version: b[0] = 0
+// - Valid traceID prefixed with 0: b[1] = 0
+// - Valid spanID prefixed with 1: b[18] = 1
+// - Valid traceFlags prefixed with 2: b[27] = 2
+func fromBinary(b []byte) (oteltrace.SpanContext, bool) {
+	if len(b) != 29 || b[0] != 0 || b[1] != 0 || b[18] != 1 || b[27] != 2 {
+		return oteltrace.SpanContext{}, false
+	}
+
+	return oteltrace.SpanContext{}.WithTraceID(
+		oteltrace.TraceID(b[2:18])).WithSpanID(
+		oteltrace.SpanID(b[19:27])).WithTraceFlags(
+		oteltrace.TraceFlags(b[28])).WithRemote(true), true
+}