How to create a global/catch-all error

[jojohanhannesnes]

Hi,
I'm currently learning axum and having a hard time trying to create a global/catch-all error on my routes.
I want to achieve something similiar in expressjs where i can just put another routes/layer at the end of the router that can catch every issues on the app. I have found something similiar like fallback, just wanted some routes that's get triggered when there's an error (even before the request gets to the handler).

The reason i wanted to implement this is because i found an error when writing the route, if i put the layer and routes in the wrong order, when hitting the api i'll be getting some error with like Missing request extension: Extension of type `entity::user::Model` was not found. Perhaps you forgot to add it? See `axum::Extension` . I wanted to convert that (or any other kind of error) message into an custom error response that i already have

Here's my current code, for context

// main.rs
async fn server() {
    let connection_string = (utils::constants::DATABASE_URL).clone();
    let db: DatabaseConnection = Database::connect(connection_string).await.unwrap();
    init_cron();
    tracing_subscriber::fmt().with_target(false).init();

    let app: Router = Router::new()
        .route("/", get(|| async {}))
        .merge(routes::user::routes())
        .merge(routes::expenses::routes())
        .route_layer(middleware::from_fn(utils::guards::guard))
        .merge(routes::expenses::routes())
        .merge(routes::auth::routes())
        .layer(Extension(db))
        .layer(
            TraceLayer::new_for_http()
                .make_span_with(trace::DefaultMakeSpan::new().level(Level::INFO))
                .on_response(trace::DefaultOnResponse::new().level(Level::INFO)),
        )
        .fallback(handler_404);
        // wanted to add the catch-all error handler here
    let addr = SocketAddr::from(([127, 0, 0, 1], 3000));
    tracing::info!("listening on {}", addr);
    axum::Server::bind(&addr)
        .serve(app.into_make_service())
        .await
        .unwrap()
}

async fn handler_404() -> impl IntoResponse {
    (
        StatusCode::NOT_FOUND,
        "The requested resource was not found",
    )
}

// error.rs
use axum::{
    http::{header, StatusCode, Method, Uri},
    response::IntoResponse,
    Json, BoxError,
};
use serde_json::json;
use tower::timeout::error::Elapsed;

pub struct APIError {
    pub message: String,
    pub status_code: StatusCode,
    pub error_code: Option<i8>,
}

impl IntoResponse for APIError {
    fn into_response(self) -> axum::response::Response {
        let status_code = self.status_code;
        (status_code, 
            [(header::CONTENT_TYPE, "application/json")],
            Json(json!({"StatusCode": self.status_code.as_u16(), "ErrorCode": self.error_code, "Message": self.message}))
        ).into_response()
    }
}

this is the example i'm trying to duplicate

function errorHandler (err, req, res, next) {
  res.status(500)
  res.render('error', { error: err })
}

would appreciate any help, thanks!

[engineerhead]

I am in the same boat as yours. Looking to find a way to have a global middleware.

[antmelnyk]

Same. Was looking into a simple way to handle all deserialize errors from extractors in one place.

[davidpdrsn]

axum currently doesn’t have a way catch any possible error.

See https://github.com/tokio-rs/axum/tree/main/examples/customize-extractor-error for how to customize the response of extractors.

Generally you shouldn’t need to customize the response from Extension because that error should never reach the end user. That is always a programmer error that should be caught by your automated tests.

Id also recommend using https://docs.rs/axum/0.6.20/axum/struct.Router.html#method.with_state instead of Extension.

[jojohanhannesnes]

Hi @davidpdrsn , thanks for the response, i assume the recommended link is also related to this #1830? i'd take a look at both links you mentioned. Once again thanks!