Method writeHeader

internal/transport/http2_server.go:1011–1038

WriteHeader sends the header metadata md back to the client.

(s *ServerStream, md metadata.MD)

// WriteHeader sends the header metadata md back to the client.
func (t *http2Server) writeHeader(s *ServerStream, md metadata.MD) error {
	s.hdrMu.Lock()
	defer s.hdrMu.Unlock()
	if s.getState() == streamDone {
		return t.streamContextErr(s)
	}

	if s.updateHeaderSent() {
		return ErrIllegalHeaderWrite
	}

	if md.Len() > 0 {
		if s.header.Len() > 0 {
			s.header = metadata.Join(s.header, md)
		} else {
			s.header = md
		}
	}
	if err := t.writeHeaderLocked(s); err != nil {
		switch e := err.(type) {
		case ConnectionError:
			return status.Error(codes.Unavailable, e.Desc)
		default:
			return status.Convert(err).Err()
		}
	}
	return nil
}

func (t *http2Server) writeHeaderLocked(s *ServerStream) error {
	// TODO(mmukhi): Benchmark if the performance gets better if count the metadata and other header fields