Doubt and error about using axum and tonic together

[frederikhors]

I'm trying to create a little Grpc-Web Rust server using axum and tonic.

I'm new both to Rust and Grpc.

I managed to generate all the rust code from proto files.

THE REPOSITORY IS HERE: https://github.com/frederikhors/issue-tonic-web

The issue I'm having is when I try to create the grpc server inside another function.

What should I use here? https://github.com/frederikhors/issue-tonic-web/blob/main/src/routes/grpc.rs#L51

pub fn new_grpc_server() -> Router {
    // I need to expose these services as grpc-web (using tonic_web I think)

    // let server = tonic_web::enable(GreeterServer::new(GrpcServiceImpl::default()));

    let server = tonic::transport::Server::builder()
        .add_service(HelloGreeterServer::new(HelloServiceImpl::default()))
        .add_service(WorldGreeterServer::new(WorldServiceImpl::default()));

    server
}

Issues

1. I don't know what to use in axum route, given the present error:

   error[E0308]: mismatched types
     --> src\main.rs:16:9
       |
   13  |     api = api.route(
       |               ----- arguments to this method are incorrect
   ...
   16  |         axum::routing::any_service(grpc_server.into_service()),
       |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `MethodRouter<_, _>`, found `MethodRouter<_, Body, Box<...>>`
       |
       = note: expected struct `MethodRouter<_, _, Infallible>`
                 found struct `MethodRouter<_, axum::body::Body, Box<(dyn std::error::Error + Send + Sync + 'static)>>`
       |
   122 |     pub fn route(mut self, path: &str, method_router: MethodRouter<S, B>) -> Self {
       |            ^^^^^
   

   for the code:

   async fn main() {
       let mut api = axum::Router::new().route("/api", get(|| async { "Hello, World!" }));
   
       let grpc_server = grpc::new_grpc_server();
   
       api = api.route(
           "/*rpc",
           // I don't know what to use here
           axum::routing::any_service(grpc_server.into_service()),
       );
   
       let addr = SocketAddr::from(([0, 0, 0, 0], 3000));
   
       axum::Server::bind(&addr)
           .serve(api.into_make_service())
           .await
           .unwrap();
   }

2. Is axum::routing::any_service necessary?

3. I don't know how to use tonic_web to expose the grpc-web

I can also PR adding an example in axum repo for this as soon I understand how to do.

Thanks in advance!

[davidpdrsn]

Like my other example you need to use HandleErrorLayer

[davidpdrsn]

Why do you need it in a function?

[frederikhors]

Because this is a small example and I need to organize the immense code base we have... :(

[davidpdrsn]

I'd just leave it inline. You can try to use impl Future to avoid making the async block but not sure it's possible.

[frederikhors]

Can I please ask you what these lines do?

let grpc = HandleErrorLayer::new(|err: BoxError| async move {
    tracing::error!(err, "grpc service failed");
    // from https://docs.rs/tonic/latest/src/tonic/status.rs.html#100
    let internal_error_code = 13;
    [("grpc-status", internal_error_code)]
})

[frederikhors]

I think I just found out reading https://docs.rs/axum/latest/axum/error_handling/index.html.