rpc_util: add bytes pool for the parser

rpc_util.go

@@ -574,9 +574,7 @@ func (p *parser) recvMsg(maxReceiveMessageSize int) (pf payloadFormat, msg []byt
 	if int(length) > maxReceiveMessageSize {
 		return 0, nil, status.Errorf(codes.ResourceExhausted, "grpc: received message larger than max (%d vs. %d)", length, maxReceiveMessageSize)
 	}
-	// TODO(bradfitz,zhaoq): garbage. reuse buffer after proto decoding instead
-	// of making it for each message:
-	msg = make([]byte, int(length))
+	msg = pool.Get(int(length))
 	if _, err := p.r.Read(msg); err != nil {
 		if err == io.EOF {
 			err = io.ErrUnexpectedEOF
@@ -689,12 +687,12 @@ type payloadInfo struct {
 }
 
 func recvAndDecompress(p *parser, s *transport.Stream, dc Decompressor, maxReceiveMessageSize int, payInfo *payloadInfo, compressor encoding.Compressor) ([]byte, error) {
-	pf, d, err := p.recvMsg(maxReceiveMessageSize)
+	pf, buf, err := p.recvMsg(maxReceiveMessageSize)
 	if err != nil {
 		return nil, err
 	}
 	if payInfo != nil {
-		payInfo.wireLength = len(d)
+		payInfo.wireLength = len(buf)
 	}
 
 	if st := checkRecvPayload(pf, s.RecvCompress(), compressor != nil || dc != nil); st != nil {
@@ -706,10 +704,10 @@ func recvAndDecompress(p *parser, s *transport.Stream, dc Decompressor, maxRecei
 		// To match legacy behavior, if the decompressor is set by WithDecompressor or RPCDecompressor,
 		// use this decompressor as the default.
 		if dc != nil {
-			d, err = dc.Do(bytes.NewReader(d))
-			size = len(d)
+			buf, err = dc.Do(bytes.NewReader(buf))
+			size = len(buf)
 		} else {
-			d, size, err = decompress(compressor, d, maxReceiveMessageSize)
+			buf, size, err = decompress(compressor, buf, maxReceiveMessageSize)
 		}
 		if err != nil {
 			return nil, status.Errorf(codes.Internal, "grpc: failed to decompress the received message: %v", err)
@@ -720,7 +718,7 @@ func recvAndDecompress(p *parser, s *transport.Stream, dc Decompressor, maxRecei
 			return nil, status.Errorf(codes.ResourceExhausted, "grpc: received message after decompression larger than max (%d vs. %d)", size, maxReceiveMessageSize)
 		}
 	}
-	return d, nil
+	return buf, nil
 }
 
 // Using compressor, decompress d, returning data and size.
@@ -755,16 +753,18 @@ func decompress(compressor encoding.Compressor, d []byte, maxReceiveMessageSize
 // dc takes precedence over compressor.
 // TODO(dfawley): wrap the old compressor/decompressor using the new API?
 func recv(p *parser, c baseCodec, s *transport.Stream, dc Decompressor, m interface{}, maxReceiveMessageSize int, payInfo *payloadInfo, compressor encoding.Compressor) error {
-	d, err := recvAndDecompress(p, s, dc, maxReceiveMessageSize, payInfo, compressor)
+	buf, err := recvAndDecompress(p, s, dc, maxReceiveMessageSize, payInfo, compressor)
 	if err != nil {
 		return err
 	}
-	if err := c.Unmarshal(d, m); err != nil {
+	if err := c.Unmarshal(buf, m); err != nil {
 		return status.Errorf(codes.Internal, "grpc: failed to unmarshal the received message: %v", err)
 	}
 	if payInfo != nil {
-		payInfo.uncompressedBytes = d
+		payInfo.uncompressedBytes = make([]byte, len(buf))
+		copy(payInfo.uncompressedBytes, buf)
 	}
+	pool.Put(&buf)
 	return nil
 }
 
@@ -914,3 +914,28 @@ const (
 )
 
 const grpcUA = "grpc-go/" + Version
+
+type bytesPool struct {
+	sync.Pool
+}
+
+func (p *bytesPool) Get(size int) []byte {
+	bs := p.Pool.Get().(*[]byte)
+	if cap(*bs) < size {
+		*bs = make([]byte, size)
+	}
+
+	return (*bs)[:size]
+}
+
+func (p *bytesPool) Put(bs *[]byte) {
+	p.Pool.Put(bs)
+}
+
+var pool = bytesPool{
+	sync.Pool{
+		New: func() interface{} {
+			return new([]byte)
+		},
+	},
+}