carrier.go

@@ -1,6 +1,10 @@
 package kgo
 
 import (
+	"net/http"
+	"slices"
+	"strings"
+
 	"github.com/twmb/franz-go/pkg/kgo"
 	"go.unistack.org/micro/v3/metadata"
 )
@@ -53,24 +57,37 @@ func (c RecordCarrier) Keys() []string {
 	return out
 }
 
-func setHeaders(r *kgo.Record, md metadata.Metadata) {
+func setHeaders(r *kgo.Record, md metadata.Metadata, exclude ...string) {
 	seen := make(map[string]struct{})
+
 loop:
 	for k, v := range md {
+		k = http.CanonicalHeaderKey(k)
+
+		if _, ok := seen[k]; ok {
+			continue loop
+		}
+
+		if slices.ContainsFunc(exclude, func(s string) bool {
+			return strings.EqualFold(s, k)
+		}) {
+			continue loop
+		}
+
 		for i := 0; i < len(r.Headers); i++ {
-			if r.Headers[i].Key == k {
+			if strings.EqualFold(r.Headers[i].Key, k) {
 				// Key exist, update the value.
 				r.Headers[i].Value = []byte(v)
 				continue loop
-			} else if _, ok := seen[k]; ok {
-				continue loop
 			}
+		}
+
 		// Key does not exist, append new header.
 		r.Headers = append(r.Headers, kgo.RecordHeader{
 			Key:   k,
 			Value: []byte(v),
 		})
+
 		seen[k] = struct{}{}
 	}
-	}
 }

kgo.go

@@ -6,7 +6,6 @@ import (
 	"errors"
 	"fmt"
 	"math/rand/v2"
-	"net/http"
 	"strings"
 	"sync"
 	"sync/atomic"
@@ -279,14 +278,14 @@ func (k *Broker) publish(ctx context.Context, msgs []*broker.Message, opts ...br
 
 	for _, msg := range msgs {
 		rec := &kgo.Record{Context: ctx, Key: key}
+
 		rec.Topic, _ = msg.Header.Get(metadata.HeaderTopic)
 		msg.Header.Del(metadata.HeaderTopic)
+
 		k.opts.Meter.Counter(semconv.PublishMessageInflight, "endpoint", rec.Topic, "topic", rec.Topic).Inc()
 		if options.BodyOnly || k.opts.Codec.String() == "noop" {
 			rec.Value = msg.Body
-			for k, v := range msg.Header {
+			setHeaders(rec, msg.Header)
-				rec.Headers = append(rec.Headers, kgo.RecordHeader{Key: http.CanonicalHeaderKey(k), Value: []byte(v)})
-			}
 		} else {
 			rec.Value, err = k.opts.Codec.Marshal(msg)
 			if err != nil {

tracer.go

@@ -68,7 +68,7 @@ func (m *hookTracer) OnProduceRecordBuffered(r *kgo.Record) {
 		r.Context, _ = m.tracer.Start(r.Context, "sdk.broker", opts...)
 	}
 
-	setHeaders(r, omd)
+	setHeaders(r, omd, metadata.HeaderContentType)
 }
 
 // OnProduceRecordUnbuffered continues and ends the "publish" span for an
@@ -135,7 +135,7 @@ func (m *hookTracer) OnFetchRecordBuffered(r *kgo.Record) {
 		r.Context, _ = m.tracer.Start(r.Context, "sdk.broker", opts...)
 	}
 
-	setHeaders(r, omd)
+	setHeaders(r, omd, metadata.HeaderContentType)
 }
 
 // OnFetchRecordUnbuffered continues and ends the "receive" span for an