Axum route can not add layer of tower

[Raymond0331]

create layer of tower:

    let cache: Cache = Arc::new(Mutex::new(LruCache::new(1024)));
    let middleware_stack = ServiceBuilder::new()
    // timeout all requests after 10 seconds
    .timeout(Duration::from_secs(10))
    // add high level tracing of requests and responses
    .layer(TraceLayer::new_for_http())
    // compression responses
    .layer(CompressionLayer::new())
    .layer(AddExtensionLayer::new(cache))
    // convert the `ServiceBuilder` into a `tower::Layer`
    .into_inner();

and then axum route add this layer:

let app = Router::new() .route("/image/:spec/:url", get(generate)) .layer(middleware_stack);

report an issue like the below:

error[E0277]: the trait bound Infallible: From<Box<(dyn StdError + Send + Sync + 'static)>> is not satisfied
--> src/main.rs:78:12
|
78 | .layer(middleware_stack);
| ----- ^^^^^^^^^^^^^^^^ the trait From<Box<(dyn StdError + Send + Sync + 'static)>> is not implemented for Infallible
| |
| required by a bound introduced by this call
|
= help: the trait From<!> is implemented for Infallible
= note: required for Box<(dyn StdError + Send + Sync + 'static)> to implement Into<Infallible>
note: required by a bound in Router::<S, B>::layer
--> /Users/ray/.asdf/installs/rust/1.52.0/registry/src/github.com-1ecc6299db9ec823/axum-0.6.1/src/routing/mod.rs:319:62
|
319 | <L::Service as Service<Request>>::Error: Into + 'static,
| ^^^^^^^^^^^^^^^^ required by this bound in Router::<S, B>::layer

[davidpdrsn]

Are you the same person that asked in Discord?

It looks like you are using the Timeout middleware from tower, which has an Error type of Box<dyn Error + ...>. Axum requires your middlewares to have an Error type of Infallible, because usually an error at the tower service level is not what you want (here a timeout would immediately close the client connection, instead of sending a timeout HTTP response).

You can either use axum's HandleErrorLayer to map the error into a response, or tower-http's timeout middleware https://docs.rs/tower-http/latest/tower_http/timeout/index.html as they don't change the service error type.