perf(sdk-go): reduce websocket order dispatch allocations

packages/sdk-go/websocket/client_dispatch.go

@@ -52,23 +52,21 @@ func (c *Client) dispatchFrame(stop <-chan struct{}, payload []byte, generation
 	// the explicit event discriminator before the heuristic market-data probes
 	// below; otherwise an order update can be silently delivered as a trade.
 	if bytes.Contains(payload, bOrder) || bytes.Contains(payload, bOrderUpdate) {
-		var eventEnvelope map[string]json.RawMessage
-		if err := json.Unmarshal(payload, &eventEnvelope); err == nil {
-			var explicitType string
-			if rawType, ok := eventEnvelope["e"]; ok {
-				_ = json.Unmarshal(rawType, &explicitType)
-			}
-			if explicitType == "order" || explicitType == "orderUpdate" {
-				var order OrderEvent
-				if err := json.Unmarshal(payload, &order); err == nil {
-					for _, subs := range tables.orderSubs {
-						for _, sub := range subs {
-							sub.send(stop, &order)
-						}
+		var eventEnvelope struct {
+			EventType string `json:"e"`
+			EventTime int64  `json:"E"`
+		}
+		if err := json.Unmarshal(payload, &eventEnvelope); err == nil &&
+			(eventEnvelope.EventType == "order" || eventEnvelope.EventType == "orderUpdate") {
+			var order OrderEvent
+			if err := json.Unmarshal(payload, &order); err == nil {
+				for _, subs := range tables.orderSubs {
+					for _, sub := range subs {
+						sub.send(stop, &order)
 					}
 				}
-				return nil
 			}
+			return nil
 		}
 	}
 

packages/sdk-go/websocket/client_dispatch_bench_test.go

@@ -0,0 +1,43 @@
+package websocket
+
+import "testing"
+
+var dispatchBenchPayloads = map[string][]byte{
+	"depth": []byte(
+		`{"e":"depthUpdate","E":1720000000000,"s":"BTCUSD","U":100,"u":101,"b":[["65000.00","1.25"],["64999.50","2.50"]],"a":[["65001.00","0.75"],["65002.00","3.00"]]}`,
+	),
+	"trade": []byte(
+		`{"e":"trade","E":1720000000000,"s":"BTCUSD","t":123456,"p":"65000.50","q":"0.125","T":1720000000000,"m":false}`,
+	),
+	"ticker": []byte(
+		`{"e":"bookTicker","E":1720000000000,"s":"BTCUSD","b":"65000.00","B":"1.25","a":"65001.00","A":"0.75"}`,
+	),
+	"order": []byte(
+		`{"e":"orderUpdate","E":1720000000000,"s":"BTCUSD","i":12345,"t":777,"S":"BUY","X":"NEW","p":"65000.00","q":"0.10"}`,
+	),
+}
+
+func newDispatchBenchClient() *Client {
+	client := NewClient("wss://ws.gemini.com")
+	client.state.Store(int32(StateConnected))
+	return client
+}
+
+func BenchmarkDispatchFrame(b *testing.B) {
+	for name, payload := range dispatchBenchPayloads {
+		b.Run(name, func(b *testing.B) {
+			client := newDispatchBenchClient()
+			stop := make(chan struct{})
+
+			b.ReportAllocs()
+			b.SetBytes(int64(len(payload)))
+			b.ResetTimer()
+
+			for i := 0; i < b.N; i++ {
+				if err := client.dispatchFrame(stop, payload, 0); err != nil {
+					b.Fatal(err)
+				}
+			}
+		})
+	}
+}

packages/sdk-go/websocket/client_dispatch_internal_test.go

@@ -16,10 +16,13 @@ func TestDispatchFrame_OrderUpdateWithTradeIDRemainsOrderEvent(t *testing.T) {
 	client.subTables.Store(tables)
 	client.subsMu.Unlock()
 
-	client.dispatchFrame(make(chan struct{}), []byte(`{"e":"orderUpdate","s":"BTCUSD","t":777,"i":12345,"S":"BUY","X":"NEW"}`), 0)
+	client.dispatchFrame(make(chan struct{}), []byte(`{"e":"orderUpdate","E":1720000000000,"s":"BTCUSD","t":777,"i":12345,"S":"BUY","X":"NEW"}`), 0)
 	select {
 	case event := <-orderSub.ch:
-		if event.EventType != "orderUpdate" || event.TradeID != 777 || event.OrderID != 12345 {
+		if event.EventType != "orderUpdate" ||
+			event.EventTime != 1720000000000 ||
+			event.TradeID != 777 ||
+			event.OrderID != 12345 {
 			t.Fatalf("unexpected order event: %+v", event)
 		}
 	case <-time.After(time.Second):