fixup tracing

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

tracer.go

@@ -6,6 +6,7 @@ import (
 
 	"github.com/twmb/franz-go/pkg/kgo"
 	semconv "go.opentelemetry.io/otel/semconv/v1.18.0"
+	"go.unistack.org/micro/v3/metadata"
 	"go.unistack.org/micro/v3/tracer"
 )
 
@@ -44,8 +45,21 @@ func (m *hookTracer) OnProduceRecordBuffered(r *kgo.Record) {
 		tracer.WithSpanLabels(attrs...),
 		tracer.WithSpanKind(tracer.SpanKindProducer),
 	}
+
+	if r.Context == nil {
+		r.Context = context.Background()
+	}
+
+	md, ok := metadata.FromOutgoingContext(r.Context)
+	if !ok {
+		md = metadata.New(len(r.Headers))
+	}
+	for _, h := range r.Headers {
+		md.Set(h.Key, string(h.Value))
+	}
+
 	// Start the "publish" span.
-	ctx, _ := m.tracer.Start(r.Context, r.Topic+" publish", opts...)
+	ctx, _ := m.tracer.Start(metadata.NewOutgoingContext(r.Context, md), r.Topic+" publish", opts...)
 	// Inject the span context into the record.
 	// t.propagators.Inject(ctx, NewRecordCarrier(r))
 	// Update the record context.
@@ -99,10 +113,18 @@ func (m *hookTracer) OnFetchRecordBuffered(r *kgo.Record) {
 	if r.Context == nil {
 		r.Context = context.Background()
 	}
+	md, ok := metadata.FromIncomingContext(r.Context)
+	if !ok {
+		md = metadata.New(len(r.Headers))
+	}
+	for _, h := range r.Headers {
+		md.Set(h.Key, string(h.Value))
+	}
+
 	// Extract the span context from the record.
 	// ctx := t.propagators.Extract(r.Context, NewRecordCarrier(r))
 	// Start the "receive" span.
-	newCtx, _ := m.tracer.Start(r.Context, r.Topic+" receive", opts...)
+	newCtx, _ := m.tracer.Start(metadata.NewIncomingContext(r.Context, md), r.Topic+" receive", opts...)
 	// Update the record context.
 	r.Context = newCtx
 }
@@ -148,6 +170,14 @@ func (m *hookTracer) WithProcessSpan(r *kgo.Record) (context.Context, tracer.Spa
 	if r.Context == nil {
 		r.Context = context.Background()
 	}
+	md, ok := metadata.FromIncomingContext(r.Context)
+	if !ok {
+		md = metadata.New(len(r.Headers))
+	}
+	for _, h := range r.Headers {
+		md.Set(h.Key, string(h.Value))
+	}
+
 	// Start a new span using the provided context and options.
 	return m.tracer.Start(r.Context, r.Topic+" process", opts...)
 }