chore: remove unnecessary heap-allocation in otelgrpc (open-telemetry#8074)

Co-authored-by: Damien Mathieu <[email protected]>

Author: etilite

instrumentation/google.golang.org/grpc/otelgrpc/metadata_supplier.go

@@ -15,21 +15,21 @@ type metadataSupplier struct {
 }
 
 // assert that metadataSupplier implements the TextMapCarrier interface.
-var _ propagation.TextMapCarrier = &metadataSupplier{}
+var _ propagation.TextMapCarrier = metadataSupplier{}
 
-func (s *metadataSupplier) Get(key string) string {
+func (s metadataSupplier) Get(key string) string {
 	values := s.metadata.Get(key)
 	if len(values) == 0 {
 		return ""
 	}
 	return values[0]
 }
 
-func (s *metadataSupplier) Set(key, value string) {
+func (s metadataSupplier) Set(key, value string) {
 	s.metadata.Set(key, value)
 }
 
-func (s *metadataSupplier) Keys() []string {
+func (s metadataSupplier) Keys() []string {
 	out := make([]string, 0, len(s.metadata))
 	for key := range s.metadata {
 		out = append(out, key)
@@ -42,7 +42,7 @@ func inject(ctx context.Context, propagators propagation.TextMapPropagator) cont
 	if !ok {
 		md = metadata.MD{}
 	}
-	propagators.Inject(ctx, &metadataSupplier{
+	propagators.Inject(ctx, metadataSupplier{
 		metadata: md,
 	})
 	return metadata.NewOutgoingContext(ctx, md)
@@ -54,7 +54,7 @@ func extract(ctx context.Context, propagators propagation.TextMapPropagator) con
 		md = metadata.MD{}
 	}
 
-	return propagators.Extract(ctx, &metadataSupplier{
+	return propagators.Extract(ctx, metadataSupplier{
 		metadata: md,
 	})
 }

instrumentation/google.golang.org/grpc/otelgrpc/metadata_supplier_bench_test.go

@@ -0,0 +1,29 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package otelgrpc
+
+import (
+	"testing"
+
+	"go.opentelemetry.io/otel"
+)
+
+func BenchmarkMetadataSupplier(b *testing.B) {
+	ctx := b.Context()
+	propagator := otel.GetTextMapPropagator()
+
+	b.Run("extract", func(b *testing.B) {
+		b.ReportAllocs()
+		for b.Loop() {
+			_ = extract(ctx, propagator)
+		}
+	})
+
+	b.Run("inject", func(b *testing.B) {
+		b.ReportAllocs()
+		for b.Loop() {
+			_ = inject(ctx, propagator)
+		}
+	})
+}

instrumentation/google.golang.org/grpc/otelgrpc/metadata_supplier_test.go

@@ -14,7 +14,7 @@ func TestMetadataSupplier(t *testing.T) {
 	md := metadata.New(map[string]string{
 		"k1": "v1",
 	})
-	ms := &metadataSupplier{md}
+	ms := metadataSupplier{md}
 
 	v1 := ms.Get("k1")
 	assert.Equal(t, "v1", v1)
@@ -25,4 +25,8 @@ func TestMetadataSupplier(t *testing.T) {
 	v2 := ms.Get("k2")
 	assert.Equal(t, "v1", v1)
 	assert.Equal(t, "v2", v2)
+
+	wantKeys := []string{"k1", "k2"}
+	keys := ms.Keys()
+	assert.ElementsMatch(t, wantKeys, keys)
 }

instrumentation/google.golang.org/grpc/otelgrpc/stats_handler_bench_test.go

@@ -141,3 +141,39 @@ func BenchmarkServerHandler_HandleRPC_NoOp_End(b *testing.B) {
 func BenchmarkServerHandler_HandleRPC_NoOp_Nil(b *testing.B) {
 	benchmarkServerHandlerHandleRPCNoOp(b, nil)
 }
+
+func BenchmarkServerHandler_TagRPCNoOp(b *testing.B) {
+	handler := NewServerHandler(
+		WithTracerProvider(tracenoop.NewTracerProvider()),
+		WithMeterProvider(metricnoop.NewMeterProvider()),
+		WithMessageEvents(ReceivedEvents, SentEvents),
+	)
+	ctx := b.Context()
+
+	tagInfo := &stats.RPCTagInfo{
+		FullMethodName: "/package.service/method",
+	}
+
+	b.ReportAllocs()
+	for b.Loop() {
+		_ = handler.TagRPC(ctx, tagInfo)
+	}
+}
+
+func BenchmarkClientHandler_TagRPCNoOp(b *testing.B) {
+	handler := NewClientHandler(
+		WithTracerProvider(tracenoop.NewTracerProvider()),
+		WithMeterProvider(metricnoop.NewMeterProvider()),
+		WithMessageEvents(ReceivedEvents, SentEvents),
+	)
+	ctx := b.Context()
+
+	tagInfo := &stats.RPCTagInfo{
+		FullMethodName: "/package.service/method",
+	}
+
+	b.ReportAllocs()
+	for b.Loop() {
+		_ = handler.TagRPC(ctx, tagInfo)
+	}
+}