Use a buffer pool to reduce contentions in tls wrapper

internal/common/tls.go

@@ -1,6 +1,7 @@
 package common
 
 import (
+	"bytes"
 	"encoding/binary"
 	"io"
 	"net"
@@ -36,18 +37,15 @@ func AddRecordLayer(input []byte, typ byte, ver uint16) []byte {
 
 type TLSConn struct {
 	net.Conn
-	writeM   sync.Mutex
-	writeBuf []byte
+	writeBufPool sync.Pool
 }
 
 func NewTLSConn(conn net.Conn) *TLSConn {
-	writeBuf := make([]byte, initialWriteBufSize)
-	writeBuf[0] = ApplicationData
-	writeBuf[1] = byte(VersionTLS13 >> 8)
-	writeBuf[2] = byte(VersionTLS13 & 0xFF)
 	return &TLSConn{
-		Conn:     conn,
-		writeBuf: writeBuf,
+		Conn: conn,
+		writeBufPool: sync.Pool{New: func() interface{} {
+			return new(bytes.Buffer)
+		}},
 	}
 }
 
@@ -95,13 +93,16 @@ func (tls *TLSConn) Read(buffer []byte) (n int, err error) {
 
 func (tls *TLSConn) Write(in []byte) (n int, err error) {
 	msgLen := len(in)
-	tls.writeM.Lock()
-	tls.writeBuf = append(tls.writeBuf[:5], in...)
-	tls.writeBuf[3] = byte(msgLen >> 8)
-	tls.writeBuf[4] = byte(msgLen & 0xFF)
-	n, err = tls.Conn.Write(tls.writeBuf[:recordLayerLength+msgLen])
-	tls.writeM.Unlock()
-	return n - recordLayerLength, err
+	writeBuf := tls.writeBufPool.Get().(*bytes.Buffer)
+	writeBuf.WriteByte(ApplicationData)
+	writeBuf.WriteByte(byte(VersionTLS13 >> 8))
+	writeBuf.WriteByte(byte(VersionTLS13 & 0xFF))
+	writeBuf.WriteByte(byte(msgLen >> 8))
+	writeBuf.WriteByte(byte(msgLen & 0xFF))
+	writeBuf.Write(in)
+	i, err := writeBuf.WriteTo(tls.Conn)
+	tls.writeBufPool.Put(writeBuf)
+	return int(i - recordLayerLength), err
 }
 
 func (tls *TLSConn) Close() error {