7f752bf263
With this changeset, ttrpc can now handle mutliple outstanding requests and responses on the same connection without blocking. On the server-side, we dispatch a goroutine per outstanding reequest. On the client side, a management goroutine dispatches responses to blocked waiters. The protocol has been changed to support this behavior by including a "stream id" that can used to identify which request a response belongs to on the client-side of the connection. With these changes, we should also be able to support streams in the future. Signed-off-by: Stephen J Day <stephen.day@docker.com>
100 lines
2.3 KiB
Go
100 lines
2.3 KiB
Go
package ttrpc
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import (
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"bufio"
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"context"
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"encoding/binary"
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"io"
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"github.com/pkg/errors"
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)
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const (
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messageHeaderLength = 10
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messageLengthMax = 8 << 10
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)
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type messageType uint8
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const (
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messageTypeRequest messageType = 0x1
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messageTypeResponse messageType = 0x2
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)
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// messageHeader represents the fixed-length message header of 10 bytes sent
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// with every request.
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type messageHeader struct {
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Length uint32 // length excluding this header. b[:4]
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StreamID uint32 // identifies which request stream message is a part of. b[4:8]
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Type messageType // message type b[8]
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Flags uint8 // reserved b[9]
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}
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func readMessageHeader(p []byte, r io.Reader) (messageHeader, error) {
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_, err := io.ReadFull(r, p[:messageHeaderLength])
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if err != nil {
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return messageHeader{}, err
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}
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return messageHeader{
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Length: binary.BigEndian.Uint32(p[:4]),
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StreamID: binary.BigEndian.Uint32(p[4:8]),
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Type: messageType(p[8]),
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Flags: p[9],
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}, nil
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}
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func writeMessageHeader(w io.Writer, p []byte, mh messageHeader) error {
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binary.BigEndian.PutUint32(p[:4], mh.Length)
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binary.BigEndian.PutUint32(p[4:8], mh.StreamID)
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p[8] = byte(mh.Type)
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p[9] = mh.Flags
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_, err := w.Write(p[:])
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return err
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}
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type channel struct {
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bw *bufio.Writer
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br *bufio.Reader
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hrbuf [messageHeaderLength]byte // avoid alloc when reading header
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hwbuf [messageHeaderLength]byte
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}
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func newChannel(w io.Writer, r io.Reader) *channel {
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return &channel{
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bw: bufio.NewWriter(w),
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br: bufio.NewReader(r),
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}
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}
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func (ch *channel) recv(ctx context.Context, p []byte) (messageHeader, error) {
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mh, err := readMessageHeader(ch.hrbuf[:], ch.br)
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if err != nil {
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return messageHeader{}, err
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}
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if mh.Length > uint32(len(p)) {
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return messageHeader{}, errors.Wrapf(io.ErrShortBuffer, "message length %v over buffer size %v", mh.Length, len(p))
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}
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if _, err := io.ReadFull(ch.br, p[:mh.Length]); err != nil {
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return messageHeader{}, errors.Wrapf(err, "failed reading message")
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}
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return mh, nil
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}
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func (ch *channel) send(ctx context.Context, streamID uint32, t messageType, p []byte) error {
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if err := writeMessageHeader(ch.bw, ch.hwbuf[:], messageHeader{Length: uint32(len(p)), StreamID: streamID, Type: t}); err != nil {
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return err
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}
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_, err := ch.bw.Write(p)
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if err != nil {
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return err
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}
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return ch.bw.Flush()
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}
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