예제 #1
0
파일: proxy.go 프로젝트: mwitkow/grpc-proxy
// ProxyStream performs a forward of a gRPC frontend stream to a backend.
func ProxyStream(director StreamDirector, logger grpclog.Logger, frontTrans transport.ServerTransport, frontStream *transport.Stream) {
	backendTrans, backendStream, err := backendTransportStream(director, frontStream.Context())
	if err != nil {
		frontTrans.WriteStatus(frontStream, grpc.Code(err), grpc.ErrorDesc(err))
		logger.Printf("proxy: Proxy.handleStream %v failed to allocate backend: %v", frontStream.Method(), err)
		return
	}
	defer backendTrans.CloseStream(backendStream, nil)

	// data coming from client call to backend
	ingressPathChan := forwardDataFrames(frontStream, backendStream, backendTrans)

	// custom header handling *must* be after some data is processed by the backend, otherwise there's a deadlock
	headerMd, err := backendStream.Header()
	if err == nil && len(headerMd) > 0 {
		frontTrans.WriteHeader(frontStream, headerMd)
	}
	// data coming from backend back to client call
	egressPathChan := forwardDataFrames(backendStream, frontStream, frontTrans)

	// wait for both data streams to complete.
	egressErr := <-egressPathChan
	ingressErr := <-ingressPathChan
	if egressErr != io.EOF || ingressErr != io.EOF {
		logger.Printf("proxy: Proxy.handleStream %v failure during transfer ingres: %v egress: %v", frontStream.Method(), ingressErr, egressErr)
		frontTrans.WriteStatus(frontStream, codes.Unavailable, fmt.Sprintf("problem in transfer ingress: %v egress: %v", ingressErr, egressErr))
		return
	}
	// handle trailing metadata
	trailingMd := backendStream.Trailer()
	if len(trailingMd) > 0 {
		frontStream.SetTrailer(trailingMd)
	}
	frontTrans.WriteStatus(frontStream, backendStream.StatusCode(), backendStream.StatusDesc())
}