chore(checkoutservice): add producer interceptor for tracing

src/accountingservice/kafka/trace_interceptor.go

@@ -28,6 +28,7 @@ func NewOTelInterceptor(groupID string) *OTelInterceptor {
 
 	oi.fixedAttrs = []attribute.KeyValue{
 		semconv.MessagingSystemKafka,
+		semconv.MessagingOperationReceive,
 		semconv.MessagingKafkaConsumerGroup(groupID),
 		semconv.NetworkTransportTCP,
 	}

src/checkoutservice/kafka/producer.go

@@ -17,6 +17,7 @@ func CreateKafkaProducer(brokers []string, log *logrus.Logger) (sarama.AsyncProd
 	saramaConfig.Version = ProtocolVersion
 	// So we can know the partition and offset of messages.
 	saramaConfig.Producer.Return.Successes = true
+	saramaConfig.Producer.Interceptors = []sarama.ProducerInterceptor{NewOTelInterceptor()}
 
 	producer, err := sarama.NewAsyncProducer(brokers, saramaConfig)
 	if err != nil {

src/checkoutservice/kafka/trace_interceptor.go

@@ -0,0 +1,60 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+package kafka
+
+import (
+	"context"
+	"fmt"
+
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/propagation"
+	semconv "go.opentelemetry.io/otel/semconv/v1.24.0"
+	"go.opentelemetry.io/otel/trace"
+
+	"github.com/IBM/sarama"
+)
+
+type OTelInterceptor struct {
+	tracer     trace.Tracer
+	fixedAttrs []attribute.KeyValue
+}
+
+// NewOTelInterceptor processes span for intercepted messages and add some
+// headers with the span data.
+func NewOTelInterceptor() *OTelInterceptor {
+	oi := OTelInterceptor{}
+	oi.tracer = otel.Tracer("github.com/open-telemetry/opentelemetry-demo/checkoutservice/sarama")
+
+	oi.fixedAttrs = []attribute.KeyValue{
+		semconv.MessagingSystemKafka,
+		semconv.MessagingOperationPublish,
+		semconv.NetworkTransportTCP,
+	}
+	return &oi
+}
+
+func (oi *OTelInterceptor) OnSend(msg *sarama.ProducerMessage) {
+	spanContext, span := oi.tracer.Start(
+		context.Background(),
+		fmt.Sprintf("%s publish", msg.Topic),
+		trace.WithSpanKind(trace.SpanKindProducer),
+		trace.WithAttributes(
+			semconv.PeerService("kafka"),
+			semconv.NetworkTransportTCP,
+			semconv.MessagingSystemKafka,
+			semconv.MessagingDestinationName(msg.Topic),
+			semconv.MessagingOperationPublish,
+			semconv.MessagingKafkaDestinationPartition(int(msg.Partition)),
+		),
+	)
+	defer span.End()
+
+	carrier := propagation.MapCarrier{}
+	propagator := otel.GetTextMapPropagator()
+	propagator.Inject(spanContext, carrier)
+
+	for key, value := range carrier {
+		msg.Headers = append(msg.Headers, sarama.RecordHeader{Key: []byte(key), Value: []byte(value)})
+	}
+}

src/checkoutservice/main.go

@@ -7,7 +7,6 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
-	semconv "go.opentelemetry.io/otel/semconv/v1.24.0"
 	"net"
 	"net/http"
 	"os"
@@ -311,7 +310,7 @@ func (cs *checkoutService) PlaceOrder(ctx context.Context, req *pb.PlaceOrderReq
 
 	// send to kafka only if kafka broker address is set
 	if cs.kafkaBrokerSvcAddr != "" {
-		cs.sendToPostProcessor(ctx, orderResult)
+		cs.sendToPostProcessor(orderResult)
 	}
 
 	resp := &pb.PlaceOrderResponse{Order: orderResult}
@@ -474,7 +473,7 @@ func (cs *checkoutService) shipOrder(ctx context.Context, address *pb.Address, i
 	return resp.GetTrackingId(), nil
 }
 
-func (cs *checkoutService) sendToPostProcessor(ctx context.Context, result *pb.OrderResult) {
+func (cs *checkoutService) sendToPostProcessor(result *pb.OrderResult) {
 	message, err := proto.Marshal(result)
 	if err != nil {
 		log.Errorf("Failed to marshal message to protobuf: %+v", err)
@@ -486,37 +485,7 @@ func (cs *checkoutService) sendToPostProcessor(ctx context.Context, result *pb.O
 		Value: sarama.ByteEncoder(message),
 	}
 
-	// Inject tracing info into message
-	span := createProducerSpan(ctx, &msg)
-	defer span.End()
-
 	cs.KafkaProducerClient.Input() <- &msg
 	successMsg := <-cs.KafkaProducerClient.Successes()
 	log.Infof("Successful to write message. offset: %v", successMsg.Offset)
 }
-
-func createProducerSpan(ctx context.Context, msg *sarama.ProducerMessage) trace.Span {
-	spanContext, span := tracer.Start(
-		ctx,
-		fmt.Sprintf("%s publish", msg.Topic),
-		trace.WithSpanKind(trace.SpanKindProducer),
-		trace.WithAttributes(
-			semconv.PeerService("kafka"),
-			semconv.NetworkTransportTCP,
-			semconv.MessagingSystemKafka,
-			semconv.MessagingDestinationName(msg.Topic),
-			semconv.MessagingOperationPublish,
-			semconv.MessagingKafkaDestinationPartition(int(msg.Partition)),
-		),
-	)
-
-	carrier := propagation.MapCarrier{}
-	propagator := otel.GetTextMapPropagator()
-	propagator.Inject(spanContext, carrier)
-
-	for key, value := range carrier {
-		msg.Headers = append(msg.Headers, sarama.RecordHeader{Key: []byte(key), Value: []byte(value)})
-	}
-
-	return span
-}