[profile] avoiding buffer to grow when normalizing tags

model/normalizer.go

@@ -107,12 +107,12 @@ func (s *Span) Normalize() error {
 		if len(k) > MaxMetaKeyLen {
 			log.Debugf("span.normalize: truncating `Meta` key (max %d chars): %s", MaxMetaKeyLen, k)
 			delete(s.Meta, k)
-			k = fmt.Sprintf("%s...", k[:MaxMetaKeyLen])
+			k = k[:MaxMetaKeyLen] + "..."
 			modified = true
 		}
 
 		if len(v) > MaxMetaValLen {
-			v = fmt.Sprintf("%s...", v[:MaxMetaValLen])
+			v = v[:MaxMetaValLen] + "..."
 			modified = true
 		}
 
@@ -125,7 +125,7 @@ func (s *Span) Normalize() error {
 		if len(k) > MaxMetricsKeyLen {
 			log.Debugf("span.normalize: truncating `Metrics` key (max %d chars): %s", MaxMetricsKeyLen, k)
 			delete(s.Metrics, k)
-			k = fmt.Sprintf("%s...", k[:MaxMetricsKeyLen])
+			k = k[:MaxMetricsKeyLen] + "..."
 
 			s.Metrics[k] = v
 		}

model/tags.go

@@ -241,8 +241,8 @@ func FilterTags(tags, groups []string) []string {
 // taken from dd-go.model.NormalizeTag
 func NormalizeTag(tag string) string {
 	// unless you just throw out unicode, this is already as fast as it gets
-	var buf bytes.Buffer
 
+	buf := bytes.NewBuffer(make([]byte, 0, 2*len(tag)))
 	lastWasUnderscore := false
 
 	for _, c := range tag {
@@ -283,12 +283,11 @@ func NormalizeTag(tag string) string {
 		}
 	}
 
-	b := buf.Bytes()
-
 	// strip trailing underscores
 	if lastWasUnderscore {
+		b := buf.Bytes()
 		return string(b[:len(b)-1])
 	}
 
-	return string(b)
+	return buf.String()
 }