Is there a way to add a custom prefix to an axum route serving tonic grpc-web?

[frederikhors]

I need to use a "prefix" for grpc routes served with tonic grpc-web and axum like:

let mut api = Router::new().route(
    "/api",
    on(MethodFilter::GET | MethodFilter::POST, my_api),
);

api = api.route(
    "/grpc/players.PlayerService/*endpoint", // I need the prefix "grpc" here as you can see
    axum::routing::any_service(grpc_server),
);

Is there a way?

[davidpdrsn]

I haven't tested it with a client but something like

// build the grpc service
let reflection_service = tonic_reflection::server::Builder::configure()
    .register_encoded_file_descriptor_set(proto::FILE_DESCRIPTOR_SET)
    .build()
    .unwrap();
let grpc = tonic::transport::Server::builder()
    .add_service(reflection_service)
    .add_service(GreeterServer::new(GrpcServiceImpl::default()))
    .into_service();
// need to map the error type to `Infallible`
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)]
})
.layer(grpc);

let app = Router::new()
    .nest_service("/grpc", grpc)
    .route("/regular-route", get(|| async { "Hello, World!" }));

let addr = SocketAddr::from(([127, 0, 0, 1], 3000));
tracing::debug!("listening on {}", addr);
axum::Server::bind(&addr)
    .serve(app.into_make_service())
    .await
    .unwrap();

should work.

Basically just using Router::nest_service.

[frederikhors]

Thanks! I'll try this as soon I first fix this: #1983.

[frederikhors]

Ok, I'm trying this, @davidpdrsn. It kinda works but I get No grpc-status found on response.. Why?

[frederikhors]

Oh, wow. Nope I wasn't using tonic_web. Sorry.

[frederikhors]

Now I need to understand how to use tonic-web though!

[frederikhors]

I'm using your code and it works:

use crate::routes::grpc;
use axum::{error_handling::HandleErrorLayer, routing::get, BoxError};
use std::net::SocketAddr;
use tower::Layer;

pub mod routes;

pub mod grpc {
    // I don't know what to return here
    pub fn new_grpc_server() -> Router {
        let router = tonic::transport::Server::builder()
            .add_service(tonic_web::enable(HelloGreeterServer::new(
                HelloServiceImpl::default(),
            )))
            .add_service(tonic_web::enable(WorldGreeterServer::new(
                WorldServiceImpl::default(),
            )));

        // From https://github.com/tokio-rs/axum/discussions/1980

        // let grpc = HandleErrorLayer::new(|err: BoxError| async move {
        //     eprintln!("{} {}", 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)]
        // })
        // .layer(server);

        router
    }
}

#[tokio::main]
async fn main() {
    let mut api = axum::Router::new().route("/api", get(|| async { "Hello, World!" }));

    let grpc_server = grpc::new_grpc_server();

    // Is it possible to move this func in grpc::new_grpc_server() ?
    let grpc = HandleErrorLayer::new(|err: BoxError| async move {
        eprintln!("{} {}", 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)]
    })
    .layer(grpc_server.into_service());

    api = api.nest_service("/*rpc", grpc);

    let addr = SocketAddr::from(([0, 0, 0, 0], 3000));

    axum::Server::bind(&addr)
        .serve(api.into_make_service())
        .await
        .unwrap();
}

But I don't know how to move the let grpc = HandleErrorLayer::new(|err: BoxError| async move { in the grpc::new_grpc_server() function.

What would be the function signature?

https://github.com/frederikhors/issue-tonic-web/blob/fix-using-nest_service/src/main.rs

[frederikhors]

I think this is the right place to ask this: #1983 (reply in thread).

[davidpdrsn]

Let's just stick to one thread plz.