tracing: fix DHT keys as string attribute not being valid utf-8

fullrt/dht.go

@@ -425,7 +425,7 @@ func workers(numWorkers int, fn func(interface{}), inputs <-chan interface{}) {
 }
 
 func (dht *FullRT) GetClosestPeers(ctx context.Context, key string) ([]peer.ID, error) {
-	_, span := internal.StartSpan(ctx, "FullRT.GetClosestPeers", trace.WithAttributes(attribute.String("Key", key)))
+	_, span := internal.StartSpan(ctx, "FullRT.GetClosestPeers", trace.WithAttributes(internal.KeyAsAttribute("Key", key)))
 	defer span.End()
 
 	kbID := kb.ConvertKey(key)
@@ -554,7 +554,7 @@ func (dht *FullRT) GetValue(ctx context.Context, key string, opts ...routing.Opt
 
 // SearchValue searches for the value corresponding to given Key and streams the results.
 func (dht *FullRT) SearchValue(ctx context.Context, key string, opts ...routing.Option) (<-chan []byte, error) {
-	ctx, span := internal.StartSpan(ctx, "FullRT.SearchValue", trace.WithAttributes(attribute.String("Key", key)))
+	ctx, span := internal.StartSpan(ctx, "FullRT.SearchValue", trace.WithAttributes(internal.KeyAsAttribute("Key", key)))
 	var good bool
 	defer func() {
 		if !good {

internal/tracing.go

@@ -3,11 +3,25 @@ package internal
 import (
 	"context"
 	"fmt"
+	"unicode/utf8"
 
+	b58 "github.com/mr-tron/base58/base58"
 	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/attribute"
 	"go.opentelemetry.io/otel/trace"
 )
 
 func StartSpan(ctx context.Context, name string, opts ...trace.SpanStartOption) (context.Context, trace.Span) {
 	return otel.Tracer("go-libp2p-kad-dht").Start(ctx, fmt.Sprintf("KademliaDHT.%s", name), opts...)
 }
+
+// KeyAsAttribute format a DHT key into a suitable tracing attribute.
+// DHT keys can be either valid utf-8 or binary, when they are derived from, for example, a multihash.
+// Tracing (and notably OpenTelemetry+grpc exporter) requires valid utf-8 for string attributes.
+func KeyAsAttribute(name string, key string) attribute.KeyValue {
+	b := []byte(key)
+	if utf8.Valid(b) {
+		return attribute.String(name, key)
+	}
+	return attribute.String(name, b58.Encode(b))
+}

lookup.go

@@ -22,7 +22,7 @@ import (
 // If the context is canceled, this function will return the context error along
 // with the closest K peers it has found so far.
 func (dht *IpfsDHT) GetClosestPeers(ctx context.Context, key string) ([]peer.ID, error) {
-	ctx, span := internal.StartSpan(ctx, "IpfsDHT.GetClosestPeers", trace.WithAttributes(attribute.String("Key", key)))
+	ctx, span := internal.StartSpan(ctx, "IpfsDHT.GetClosestPeers", trace.WithAttributes(internal.KeyAsAttribute("Key", key)))
 	defer span.End()
 
 	if key == "" {

query.go

@@ -81,7 +81,7 @@ type lookupWithFollowupResult struct {
 // After the lookup is complete the query function is run (unless stopped) against all of the top K peers from the
 // lookup that have not already been successfully queried.
 func (dht *IpfsDHT) runLookupWithFollowup(ctx context.Context, target string, queryFn queryFn, stopFn stopFn) (*lookupWithFollowupResult, error) {
-	ctx, span := internal.StartSpan(ctx, "IpfsDHT.RunLookupWithFollowup", trace.WithAttributes(attribute.String("Target", target)))
+	ctx, span := internal.StartSpan(ctx, "IpfsDHT.RunLookupWithFollowup", trace.WithAttributes(internal.KeyAsAttribute("Target", target)))
 	defer span.End()
 
 	// run the query

routing.go

@@ -34,7 +34,7 @@ import (
 // PutValue adds value corresponding to given Key.
 // This is the top level "Store" operation of the DHT
 func (dht *IpfsDHT) PutValue(ctx context.Context, key string, value []byte, opts ...routing.Option) (err error) {
-	ctx, span := internal.StartSpan(ctx, "IpfsDHT.PutValue", trace.WithAttributes(attribute.String("Key", key)))
+	ctx, span := internal.StartSpan(ctx, "IpfsDHT.PutValue", trace.WithAttributes(internal.KeyAsAttribute("Key", key)))
 	defer span.End()
 
 	if !dht.enableValues {
@@ -109,7 +109,7 @@ type recvdVal struct {
 
 // GetValue searches for the value corresponding to given Key.
 func (dht *IpfsDHT) GetValue(ctx context.Context, key string, opts ...routing.Option) (_ []byte, err error) {
-	ctx, span := internal.StartSpan(ctx, "IpfsDHT.GetValue", trace.WithAttributes(attribute.String("Key", key)))
+	ctx, span := internal.StartSpan(ctx, "IpfsDHT.GetValue", trace.WithAttributes(internal.KeyAsAttribute("Key", key)))
 	defer span.End()
 
 	if !dht.enableValues {
@@ -146,7 +146,7 @@ func (dht *IpfsDHT) GetValue(ctx context.Context, key string, opts ...routing.Op
 
 // SearchValue searches for the value corresponding to given Key and streams the results.
 func (dht *IpfsDHT) SearchValue(ctx context.Context, key string, opts ...routing.Option) (<-chan []byte, error) {
-	ctx, span := internal.StartSpan(ctx, "IpfsDHT.SearchValue", trace.WithAttributes(attribute.String("Key", key)))
+	ctx, span := internal.StartSpan(ctx, "IpfsDHT.SearchValue", trace.WithAttributes(internal.KeyAsAttribute("Key", key)))
 	var good bool
 	defer func() {
 		if !good {