Is it ok to implement async middleware in call's Box pin? #2213

kulak · 2023-09-07T17:34:19Z

kulak
Sep 7, 2023

For the past few days I've been trying to get remote JWT authentication as axum middleware. I got it working, but I am unsure of decision made.

It seems that tutorials and implementations don't put much code into Service's fn call and want to create a Future that will run in fn poll_ready.

I simply placed my async function inside fn call. I don't really see much of drawback. Is there any?

Here is quick code reference to give context of what I am talking about:

use tower::Service;
use axum::{
    response::{IntoResponse, Response},
    body::Body,
    http::{header::COOKIE, Request, StatusCode, HeaderMap, HeaderValue},
};
use futures_util::future::BoxFuture;
use std::task::{Context, Poll};
use http::Uri;
use log::error;

#[derive(Clone)]
pub struct JwtMiddleware<S> {
    pub inner: S,
    pub cookie_name: String,
    pub validate_url: Uri,
}

impl<S> Service<Request<Body>> for JwtMiddleware<S>
where
    S: Service<Request<Body>, Response = Response> + Send + 'static,
    S::Future: Send + 'static,
{
    type Response = S::Response;
    type Error = S::Error;
    // `BoxFuture` is a type alias for `Pin<Box<dyn Future + Send + 'a>>`
    type Future = BoxFuture<'static, Result<Self::Response, Self::Error>>;

    fn poll_ready(&mut self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
        self.inner.poll_ready(cx)
    }

    fn call(&mut self, request: Request<Body>) -> Self::Future {
        let headers = request.headers().clone();
        let future = self.inner.call(request);
        let cookie_name = self.cookie_name.clone();
        let validate_url = self.validate_url.clone();
        Box::pin(async move {
            let status_code = remote_auth(cookie_name, validate_url, headers).await;
            if status_code != StatusCode::OK {
                return Ok(status_code.into_response());
            }
            let response: Response = future.await?;
            Ok(response)
        })
    }
}

pub async fn remote_auth(cookie_name: String, validate_url: Uri, headers: HeaderMap<HeaderValue>) -> StatusCode {
    // omitted
}

davidpdrsn · 2023-09-07T18:13:39Z

davidpdrsn
Sep 7, 2023
Collaborator

Yes that’s fine.

0 replies

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kulak Sep 7, 2023

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davidpdrsn Sep 7, 2023 Collaborator

kulak
Sep 7, 2023

davidpdrsn
Sep 7, 2023
Collaborator