Rest + several gRPC services #1182

BratSinot · 2022-07-22T07:45:35Z

BratSinot
Jul 22, 2022

Greeting!

Can anyone help me? I took this example:
https://github.com/tokio-rs/axum/tree/main/examples/rest-grpc-multiplex/src

as base for my service. But I need more than one gRPC service. I added these lines into example:

    // build the grpc service
    let greeter = GreeterServer::new(GrpcServiceImpl::default());
    let (mut health_reporter, health_service) = tonic_health::server::health_reporter();
    health_reporter
        .set_serving::<GreeterServer<GrpcServiceImpl>>()
        .await;

    let grpc = tonic::transport::Server::builder()
        .add_service(greeter)
        .add_service(health_service)
        .into_service();

And got next error:

/Users/asinotov/.cargo/bin/cargo clippy --color=always --message-format=json-diagnostic-rendered-ansi
   Compiling example-rest-grpc-multiplex v0.1.0 (/Users/asinotov/projects/axum/examples/rest-grpc-multiplex)
error[E0271]: type mismatch resolving `<tonic::transport::server::Routes as tower::Service<hyper::Request<hyper::Body>>>::Error == std::convert::Infallible`
  --> rest-grpc-multiplex/src/main.rs:78:16
   |
78 |         .serve(tower::make::Shared::new(service))
   |          ----- ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected struct `std::boxed::Box`, found enum `std::convert::Infallible`
   |          |
   |          required by a bound introduced by this call
   |
   = note: expected struct `std::boxed::Box<(dyn std::error::Error + std::marker::Send + std::marker::Sync + 'static)>`
                found enum `std::convert::Infallible`
note: required because of the requirements on the impl of `tower::Service<hyper::Request<hyper::Body>>` for `multiplex_service::MultiplexService<axum::Router, tonic::transport::server::Routes>`
  --> rest-grpc-multiplex/src/multiplex_service.rs:44:12
   |
44 | impl<A, B> Service<Request<Body>> for MultiplexService<A, B>
   |            ^^^^^^^^^^^^^^^^^^^^^^     ^^^^^^^^^^^^^^^^^^^^^^
   = note: required because of the requirements on the impl of `hyper::service::http::HttpService<hyper::Body>` for `multiplex_service::MultiplexService<axum::Router, tonic::transport::server::Routes>`
   = note: required because of the requirements on the impl of `hyper::service::make::MakeServiceRef<hyper::server::conn::AddrStream, hyper::Body>` for `tower::make::Shared<multiplex_service::MultiplexService<axum::Router, tonic::transport::server::Routes>>`

error[E0277]: the trait bound `hyper::common::exec::Exec: hyper::common::exec::NewSvcExec<hyper::server::conn::AddrStream, tower::make::future::SharedFuture<multiplex_service::MultiplexService<axum::Router, tonic::transport::server::Routes>>, multiplex_service::MultiplexService<axum::Router, tonic::transport::server::Routes>, hyper::common::exec::Exec, hyper::server::server::NoopWatcher>` is not satisfied
  --> rest-grpc-multiplex/src/main.rs:78:50
   |
78 |           .serve(tower::make::Shared::new(service))
   |  __________________________________________________^
79 | |         .await
   | |______________^ the trait `hyper::common::exec::NewSvcExec<hyper::server::conn::AddrStream, tower::make::future::SharedFuture<multiplex_service::MultiplexService<axum::Router, tonic::transport::server::Routes>>, multiplex_service::MultiplexService<axum::Router, tonic::transport::server::Routes>, hyper::common::exec::Exec, hyper::server::server::NoopWatcher>` is not implemented for `hyper::common::exec::Exec`
   |
   = help: the trait `hyper::common::exec::NewSvcExec<I, N, S, E, W>` is implemented for `hyper::common::exec::Exec`
   = note: required because of the requirements on the impl of `futures::Future` for `axum::Server<hyper::server::conn::AddrIncoming, tower::make::Shared<multiplex_service::MultiplexService<axum::Router, tonic::transport::server::Routes>>>`
   = note: required because of the requirements on the impl of `std::future::IntoFuture` for `axum::Server<hyper::server::conn::AddrIncoming, tower::make::Shared<multiplex_service::MultiplexService<axum::Router, tonic::transport::server::Routes>>>`
help: remove the `.await`
   |
78 -         .serve(tower::make::Shared::new(service))
78 +         .serve(tower::make::Shared::new(service))
   | 

error[E0271]: type mismatch resolving `<tonic::transport::server::Routes as tower::Service<hyper::Request<hyper::Body>>>::Error == std::convert::Infallible`
  --> rest-grpc-multiplex/src/main.rs:78:10
   |
78 |         .serve(tower::make::Shared::new(service))
   |          ^^^^^ expected struct `std::boxed::Box`, found enum `std::convert::Infallible`
   |
   = note: expected struct `std::boxed::Box<(dyn std::error::Error + std::marker::Send + std::marker::Sync + 'static)>`
                found enum `std::convert::Infallible`
note: required because of the requirements on the impl of `tower::Service<hyper::Request<hyper::Body>>` for `multiplex_service::MultiplexService<axum::Router, tonic::transport::server::Routes>`
  --> rest-grpc-multiplex/src/multiplex_service.rs:44:12
   |
44 | impl<A, B> Service<Request<Body>> for MultiplexService<A, B>
   |            ^^^^^^^^^^^^^^^^^^^^^^     ^^^^^^^^^^^^^^^^^^^^^^
   = note: required because of the requirements on the impl of `hyper::service::http::HttpService<hyper::Body>` for `multiplex_service::MultiplexService<axum::Router, tonic::transport::server::Routes>`
   = note: required because of the requirements on the impl of `hyper::service::make::MakeServiceRef<hyper::server::conn::AddrStream, hyper::Body>` for `tower::make::Shared<multiplex_service::MultiplexService<axum::Router, tonic::transport::server::Routes>>`

error: aborting due to 3 previous errors

Some errors have detailed explanations: E0271, E0277.
For more information about an error, try `rustc --explain E0271`.
error: could not compile `example-rest-grpc-multiplex` due to 4 previous errors
Process finished with exit code 101

I tried change generic of errors on something else, but got no luck.

davidpdrsn · 2022-07-22T11:17:20Z

davidpdrsn
Jul 22, 2022
Collaborator

You probably need to wrap grpc in https://docs.rs/axum/latest/axum/error_handling/struct.HandleError.html since the error must be Infallible.

7 replies

BratSinot Jul 22, 2022
Author

It's similar to this example re how HandleError is applied.

In other words, there is no easy way to have HTTP and gRPC on same port?

davidpdrsn Jul 22, 2022
Collaborator

I didn't say that - there certainly is. Have a look at the example I sent and the multiplex example in the repo.

I'm afk so cannot write the code. Try and see if you can make it work.

BratSinot Jul 22, 2022
Author

I didn't say that - there certainly is. Have a look at the example I sent and the multiplex example in the repo.

I'm afk so cannot write the code. Try and see if you can make it work.

I mean what I can't get why I should write custom error handler, when I shouldn't do it in case, when I pass single gRPC service to Multiplexer.
If I write custom error handler, then I should do properly convert some error into right http response according to gRPC standard.

Moreover, I can't do event that (custom error handler), because tonic::transport::server::Routes implement Service<Request<Body>> where type Error = Box<dyn std::error::Error + Send + Sync> and I can't get StatusCode or something like that to make proper response.

davidpdrsn Jul 22, 2022
Collaborator

I mean what I can't get why I should write custom error handler, when I shouldn't do it in case, when I pass single gRPC service to Multiplexer.

Because you need to use tonic::transport::Server which changes the error type for some reason.

If I write custom error handler, then I should do properly convert some error into right http response according to gRPC standard.

You can use https://docs.rs/tonic/latest/tonic/struct.Status.html#method.to_http to create an "internal error" gRPC response.

Moreover, I can't do event that (custom error handler), because tonic::transport::server::Routes implement Service<Request> where type Error = Box<dyn std::error::Error + Send + Sync> and I can't get StatusCode or something like that to make proper response.

If an error is returned then there is no status because there is no response. Just return an internal error.

davidpdrsn Jul 22, 2022
Collaborator

Have you tried https://crates.io/crates/axum_tonic?

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Rest + several gRPC services #1182

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BratSinot Jul 22, 2022

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