Add BytesMapCarrier

propagation/propagation.go

@@ -40,6 +40,32 @@ type TextMapCarrier interface {
 	// must never be done outside of a new major release.
 }
 
+// BytesMapCarrier is a Carrier that stores propagated
+// values in a map of bytes.
+type BytesMapCarrier map[string][]byte
+
+// Compile time check the BytesMapCarrier implements the TextMapCarrier.
+var _ TextMapCarrier = BytesMapCarrier{}
+
+// Get returns the value associated with the passed key.
+func (c BytesMapCarrier) Get(key string) string {
+	return string(c[key])
+}
+
+// Set stores the key-value pair.
+func (c BytesMapCarrier) Set(key string, value string) {
+	c[key] = []byte(value)
+}
+
+// Keys lists the keys stored in this carrier.
+func (c BytesMapCarrier) Keys() []string {
+	keys := make([]string, 0, len(c))
+	for k := range c {
+		keys = append(keys, k)
+	}
+	return keys
+}
+
 // HeaderCarrier adapts http.Header to satisfy the TextMapCarrier interface.
 type HeaderCarrier http.Header
 

propagation/propagators_test.go

@@ -16,6 +16,7 @@ package propagation_test
 
 import (
 	"context"
+	"sort"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -53,6 +54,19 @@ func mustSpanIDFromHex(s string) (t trace.SpanID) {
 	return
 }
 
+func TestBytesMapCarrier(t *testing.T) {
+	carrier := make(propagation.BytesMapCarrier)
+	carrier.Set("foo", "bar")
+	carrier.Set("baz", "qux")
+
+	assert.Equal(t, carrier.Get("foo"), "bar")
+	assert.Equal(t, carrier.Get("baz"), "qux")
+
+	keys := carrier.Keys()
+	sort.Strings(keys)
+	assert.Equal(t, []string{"baz", "foo"}, keys)
+}
+
 type outOfThinAirPropagator struct {
 	t *testing.T
 }