rpc: improve the realtime notify performance by 30%

rpc/json.go

@@ -46,6 +46,17 @@ type subscriptionResult struct {
 	Result json.RawMessage `json:"result,omitempty"`
 }
 
+type subscriptionResultEnc struct {
+	ID     string `json:"subscription"`
+	Result any    `json:"result"`
+}
+
+type jsonrpcSubscriptionNotification struct {
+	Version string                `json:"jsonrpc"`
+	Method  string                `json:"method"`
+	Params  subscriptionResultEnc `json:"params"`
+}
+
 // A value of this type can a JSON-RPC request, notification, successful response or
 // error response. Which one it is depends on the fields.
 type jsonrpcMessage struct {

rpc/subscription.go

@@ -105,7 +105,7 @@ type Notifier struct {
 
 	mu           sync.Mutex
 	sub          *Subscription
-	buffer       []json.RawMessage
+	buffer       []any
 	callReturned bool
 	activated    bool
 }
@@ -129,12 +129,7 @@ func (n *Notifier) CreateSubscription() *Subscription {
 
 // Notify sends a notification to the client with the given data as payload.
 // If an error occurs the RPC connection is closed and the error is returned.
-func (n *Notifier) Notify(id ID, data interface{}) error {
-	enc, err := json.Marshal(data)
-	if err != nil {
-		return err
-	}
-
+func (n *Notifier) Notify(id ID, data any) error {
 	n.mu.Lock()
 	defer n.mu.Unlock()
 
@@ -144,9 +139,9 @@ func (n *Notifier) Notify(id ID, data interface{}) error {
 		panic("Notify with wrong ID")
 	}
 	if n.activated {
-		return n.send(n.sub, enc)
+		return n.send(n.sub, data)
 	}
-	n.buffer = append(n.buffer, enc)
+	n.buffer = append(n.buffer, data)
 	return nil
 }
 
@@ -181,16 +176,16 @@ func (n *Notifier) activate() error {
 	return nil
 }
 
-func (n *Notifier) send(sub *Subscription, data json.RawMessage) error {
-	params, _ := json.Marshal(&subscriptionResult{ID: string(sub.ID), Result: data})
-	ctx := context.Background()
-
-	msg := &jsonrpcMessage{
+func (n *Notifier) send(sub *Subscription, data any) error {
+	msg := jsonrpcSubscriptionNotification{
 		Version: vsn,
 		Method:  n.namespace + notificationMethodSuffix,
-		Params:  params,
+		Params: subscriptionResultEnc{
+			ID:     string(sub.ID),
+			Result: data,
+		},
 	}
-	return n.h.conn.writeJSON(ctx, msg, false)
+	return n.h.conn.writeJSON(context.Background(), &msg, false)
 }
 
 // A Subscription is created by a notifier and tied to that notifier. The client can use

rpc/subscription_test.go

@@ -17,12 +17,19 @@
 package rpc
 
 import (
+	"bytes"
+	"context"
 	"encoding/json"
 	"fmt"
+	"io"
+	"math/big"
 	"net"
 	"strings"
 	"testing"
 	"time"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core/types"
 )
 
 func TestNewID(t *testing.T) {
@@ -218,3 +225,56 @@ func readAndValidateMessage(in *json.Decoder) (*subConfirmation, *subscriptionRe
 		return nil, nil, fmt.Errorf("unrecognized message: %v", msg)
 	}
 }
+
+type mockConn struct {
+	enc *json.Encoder
+}
+
+// writeJSON writes a message to the connection.
+func (c *mockConn) writeJSON(ctx context.Context, msg interface{}, isError bool) error {
+	return c.enc.Encode(msg)
+}
+
+// Closed returns a channel which is closed when the connection is closed.
+func (c *mockConn) closed() <-chan interface{} { return nil }
+
+// RemoteAddr returns the peer address of the connection.
+func (c *mockConn) remoteAddr() string { return "" }
+
+// BenchmarkNotify benchmarks the performance of notifying a subscription.
+func BenchmarkNotify(b *testing.B) {
+	id := ID("test")
+	notifier := &Notifier{
+		h:         &handler{conn: &mockConn{json.NewEncoder(io.Discard)}},
+		sub:       &Subscription{ID: id},
+		activated: true,
+	}
+	msg := &types.Header{
+		ParentHash: common.HexToHash("0x01"),
+		Number:     big.NewInt(100),
+	}
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		notifier.Notify(id, msg)
+	}
+}
+
+func TestNotify(t *testing.T) {
+	out := new(bytes.Buffer)
+	id := ID("test")
+	notifier := &Notifier{
+		h:         &handler{conn: &mockConn{json.NewEncoder(out)}},
+		sub:       &Subscription{ID: id},
+		activated: true,
+	}
+	msg := &types.Header{
+		ParentHash: common.HexToHash("0x01"),
+		Number:     big.NewInt(100),
+	}
+	notifier.Notify(id, msg)
+	have := strings.TrimSpace(out.String())
+	want := `{"jsonrpc":"2.0","method":"_subscription","params":{"subscription":"test","result":{"parentHash":"0x0000000000000000000000000000000000000000000000000000000000000001","sha3Uncles":"0x0000000000000000000000000000000000000000000000000000000000000000","miner":"0x0000000000000000000000000000000000000000","stateRoot":"0x0000000000000000000000000000000000000000000000000000000000000000","transactionsRoot":"0x0000000000000000000000000000000000000000000000000000000000000000","receiptsRoot":"0x0000000000000000000000000000000000000000000000000000000000000000","logsBloom":"0x00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000","difficulty":null,"number":"0x64","gasLimit":"0x0","gasUsed":"0x0","timestamp":"0x0","extraData":"0x","mixHash":"0x0000000000000000000000000000000000000000000000000000000000000000","nonce":"0x0000000000000000","baseFeePerGas":null,"withdrawalsRoot":null,"blobGasUsed":null,"excessBlobGas":null,"parentBeaconBlockRoot":null,"hash":"0xe5fb877dde471b45b9742bb4bb4b3d74a761e2fb7cb849a3d2b687eed90fb604"}}}`
+	if have != want {
+		t.Errorf("have:\n%v\nwant:\n%v\n", have, want)
+	}
+}