How to do a 302 redirect in grpc-gateway

you could also use runtime. WithForwardResponseOption method which allows you to modify your response and response headers.

here is what I did to set Location header in response.

1. Set Location header in your GRPC method using metadata. this adds Grpc-Metadata-Location header to your response.

func (s *Server) CreatePayment(ctx context.Context, in *proto.Request) (*proto.Response, error) {
    header := metadata.Pairs("Location", url)
    grpc.SendHeader(ctx, header)

    return &proto.Response{}, nil
}

2. If Grpc-Metadata-Location header exists in your GRPC response headers, Set HTTP Location header and status code as well.

func responseHeaderMatcher(ctx context.Context, w http.ResponseWriter, resp proto.Message) error {
    headers := w.Header()
    if location, ok := headers["Grpc-Metadata-Location"]; ok {
        w.Header().Set("Location", location[0])
        w.WriteHeader(http.StatusFound)
    }

    return nil
}

3. Set this func as an Option in NewServeMux:

grpcGatewayMux := runtime.NewServeMux(
    runtime.WithForwardResponseOption(responseHeaderMatcher),
)

There's no straightforward way. But there's a workaround.

There's no conception in gRPC similar to 302. So simple error code mappings won't work fine. But you can overwrite a response forwarder per method so that it extracts redirectURL from the response and sets the HTTP status code and Location header.

https://grpc-ecosystem.github.io/grpc-gateway/docs/mapping/customizingyourgateway/#mutate-response-messages-or-set-response-headers