allocations improvements and tunnel fixes (#1248)

* reduce allocations in tunnel code

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

* another allocation fix

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

* allocate maps with len if it known

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

* allocate key for send once

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

codec.go

@@ -155,7 +155,7 @@ func (g *grpcCodec) ReadHeader(m *codec.Message, mt codec.MessageType) error {
 		m = new(codec.Message)
 	}
 	if m.Header == nil {
-		m.Header = make(map[string]string)
+		m.Header = make(map[string]string, len(md))
 	}
 	for k, v := range md {
 		m.Header[k] = strings.Join(v, ",")

grpc.go

@@ -110,13 +110,18 @@ func (g *grpcClient) next(request client.Request, opts client.CallOptions) (sele
 }
 
 func (g *grpcClient) call(ctx context.Context, node *registry.Node, req client.Request, rsp interface{}, opts client.CallOptions) error {
+	var header map[string]string
+
 	address := node.Address
 
-	header := make(map[string]string)
+	header = make(map[string]string)
 	if md, ok := metadata.FromContext(ctx); ok {
+		header = make(map[string]string, len(md))
 		for k, v := range md {
 			header[k] = v
 		}
+	} else {
+		header = make(map[string]string)
 	}
 
 	// set timeout in nanoseconds
@@ -182,13 +187,17 @@ func (g *grpcClient) call(ctx context.Context, node *registry.Node, req client.R
 }
 
 func (g *grpcClient) stream(ctx context.Context, node *registry.Node, req client.Request, opts client.CallOptions) (client.Stream, error) {
+	var header map[string]string
+
 	address := node.Address
 
-	header := make(map[string]string)
 	if md, ok := metadata.FromContext(ctx); ok {
+		header = make(map[string]string, len(md))
 		for k, v := range md {
 			header[k] = v
 		}
+	} else {
+		header = make(map[string]string)
 	}
 
 	// set timeout in nanoseconds

response.go

@@ -27,7 +27,7 @@ func (r *response) Header() map[string]string {
 	if err != nil {
 		return map[string]string{}
 	}
-	hdr := make(map[string]string)
+	hdr := make(map[string]string, len(md))
 	for k, v := range md {
 		hdr[k] = strings.Join(v, ",")
 	}