From 0c4e5a9b475cd22078b5166b6e0808deed94be34 Mon Sep 17 00:00:00 2001
From: Mikhail Mazurskiy <126021+ash2k@users.noreply.github.com>
Date: Tue, 5 Sep 2023 22:29:41 +1000
Subject: [PATCH] Preallocate slice in spanInfo() (#4262)

---
 .../google.golang.org/grpc/otelgrpc/interceptor.go    | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/instrumentation/google.golang.org/grpc/otelgrpc/interceptor.go b/instrumentation/google.golang.org/grpc/otelgrpc/interceptor.go
index 68b3473bc03..561154061fe 100644
--- a/instrumentation/google.golang.org/grpc/otelgrpc/interceptor.go
+++ b/instrumentation/google.golang.org/grpc/otelgrpc/interceptor.go
@@ -501,10 +501,13 @@ func StreamServerInterceptor(opts ...Option) grpc.StreamServerInterceptor {
 // spanInfo returns a span name and all appropriate attributes from the gRPC
 // method and peer address.
 func spanInfo(fullMethod, peerAddress string) (string, []attribute.KeyValue) {
-	attrs := []attribute.KeyValue{RPCSystemGRPC}
 	name, mAttrs := internal.ParseFullMethod(fullMethod)
+	peerAttrs := peerAttr(peerAddress)
+
+	attrs := make([]attribute.KeyValue, 0, 1+len(mAttrs)+len(peerAttrs))
+	attrs = append(attrs, RPCSystemGRPC)
 	attrs = append(attrs, mAttrs...)
-	attrs = append(attrs, peerAttr(peerAddress)...)
+	attrs = append(attrs, peerAttrs...)
 	return name, attrs
 }
 
@@ -512,7 +515,7 @@ func spanInfo(fullMethod, peerAddress string) (string, []attribute.KeyValue) {
 func peerAttr(addr string) []attribute.KeyValue {
 	host, p, err := net.SplitHostPort(addr)
 	if err != nil {
-		return []attribute.KeyValue(nil)
+		return nil
 	}
 
 	if host == "" {
@@ -520,7 +523,7 @@ func peerAttr(addr string) []attribute.KeyValue {
 	}
 	port, err := strconv.Atoi(p)
 	if err != nil {
-		return []attribute.KeyValue(nil)
+		return nil
 	}
 
 	var attr []attribute.KeyValue