Golang Stream.Trailer方法代碼示例

// recvResponse receives and parses an RPC response.
// On error, it returns the error and indicates whether the call should be retried.
//
// TODO(zhaoq): Check whether the received message sequence is valid.
func recvResponse(dopts dialOptions, t transport.ClientTransport, c *callInfo, stream *transport.Stream, reply interface{}) error {
	// Try to acquire header metadata from the server if there is any.
	var err error
	defer func() {
		if err != nil {
			if _, ok := err.(transport.ConnectionError); !ok {
				t.CloseStream(stream, err)
			}
		}
	}()
	c.headerMD, err = stream.Header()
	if err != nil {
		return err
	}
	p := &parser{r: stream}
	for {
		if err = recv(p, dopts.codec, stream, dopts.dc, reply, math.MaxInt32); err != nil {
			if err == io.EOF {
				break
			}
			return err
		}
	}
	c.trailerMD = stream.Trailer()
	return nil
}

// recvResponse receives and parses an RPC response.
// On error, it returns the error and indicates whether the call should be retried.
//
// TODO(zhaoq): Check whether the received message sequence is valid.
func recvResponse(dopts dialOptions, t transport.ClientTransport, c *callInfo, stream *transport.Stream, reply interface{}) error {
	// Try to acquire header metadata from the server if there is any.

	// 如何接受請求呢?
	// 1. 和處理的Http請求類似, 首先是: 處理Header
	var err error
	c.headerMD, err = stream.Header()
	if err != nil {
		return err
	}

	// 2. 然後處理stream
	p := &parser{r: stream}
	for {
		// stream --> (parser) --> msg --> decompress --> unmarshal --> reply
		// Iter 1: 讀取到Reply
		// Iter 2: 讀取失敗，碰到EOF
		if err = recv(p, dopts.codec, stream, dopts.dc, reply); err != nil {
			// 似乎需要等待stream的EOF
			if err == io.EOF {
				break
			}
			return err
		}
	}

	// 3. 獲取Trailer?
	c.trailerMD = stream.Trailer()
	return nil
}

// recv receives and parses an RPC response.
// On error, it returns the error and indicates whether the call should be retried.
//
// TODO(zhaoq): Check whether the received message sequence is valid.
func recv(t transport.ClientTransport, c *callInfo, stream *transport.Stream, reply proto.Message) error {
	// Try to acquire header metadata from the server if there is any.
	var err error
	c.headerMD, err = stream.Header()
	if err != nil {
		return err
	}
	p := &parser{s: stream}
	for {
		if err = recvProto(p, reply); err != nil {
			if err == io.EOF {
				break
			}
			return err
		}
	}
	c.trailerMD = stream.Trailer()
	return nil
}

// recvResponse receives and parses an RPC response.
// On error, it returns the error and indicates whether the call should be retried.
//
// TODO(zhaoq): Check whether the received message sequence is valid.
// TODO ctx is used for stats collection and processing. It is the context passed from the application.
func recvResponse(ctx context.Context, dopts dialOptions, t transport.ClientTransport, c *callInfo, stream *transport.Stream, reply interface{}) (err error) {
	// Try to acquire header metadata from the server if there is any.
	defer func() {
		if err != nil {
			if _, ok := err.(transport.ConnectionError); !ok {
				t.CloseStream(stream, err)
			}
		}
	}()
	c.headerMD, err = stream.Header()
	if err != nil {
		return
	}
	p := &parser{r: stream}
	var inPayload *stats.InPayload
	if stats.On() {
		inPayload = &stats.InPayload{
			Client: true,
		}
	}
	for {
		if err = recv(p, dopts.codec, stream, dopts.dc, reply, math.MaxInt32, inPayload); err != nil {
			if err == io.EOF {
				break
			}
			return
		}
	}
	if inPayload != nil && err == io.EOF && stream.StatusCode() == codes.OK {
		// TODO in the current implementation, inTrailer may be handled before inPayload in some cases.
		// Fix the order if necessary.
		stats.Handle(ctx, inPayload)
	}
	c.trailerMD = stream.Trailer()
	return nil
}