How to run a different reqwest in an endpoint?

[cemoktra]

I'm trying to run a HTTP request in a specific case, But it seems i cannot use await in an endpoint function.

error[E0277]: the trait bound `fn(axum::extract::Path<std::string::String>, Extension<Arc<WebServiceState<T>>>) -> impl Future {download::<T>}: Handler<axum::body::Body, _>` is not satisfied

the endpoint

async fn download<T: Send + Sync + Storage>(extract::Path((file)): extract::Path<String>, state: extract::Extension<Arc<WebServiceState<T>>>) {
...
    match surf::get("some_url").send().await {
        Ok(result) => todo!(),
        Err(_) => {
            todo!()
        },
    };
}

[davidpdrsn]

What type are you binding T to?

[davidpdrsn]

Can you share more of your code? I cannot tell what's wrong without more context and async definitely is supported within handlers.

I imagine rust cannot infer the actual type of T. In the end rust has to instantiate it to an actual type.

[davidpdrsn]

Would also help if you could post the whole error message.

[cemoktra]

I pushed the source code to:
https://github.com/cemoktra/cargolifter/blob/implement-download/src/web/service.rs#L51

error[E0277]: the trait bound `fn(axum::extract::Path<(std::string::String, std::string::String)>, Extension<Arc<WebServiceState<T>>>) -> impl Future {download::<T>}: Handler<_, _>` is not satisfied
   --> src/web/service.rs:30:78
    |
30  |             .route("/api/v1/crates/:crate_name/:crate_version/download", get(download::<T>))
    |                                                                              ^^^^^^^^^^^^^ the trait `Handler<_, _>` is not implemented for `fn(axum::extract::Path<(std::string::String, std::string::String)>, Extension<Arc<WebServiceState<T>>>) -> impl Future {download::<T>}`
    | 
   ::: /home/bastian/.cargo/registry/src/github.com-1ecc6299db9ec823/axum-0.2.4/src/handler/mod.rs:101:8
    |
101 |     H: Handler<B, T>,
    |        ------------- required by this bound in `axum::handler::get`

error[E0277]: the trait bound `fn(axum::extract::Path<(std::string::String, std::string::String)>, Extension<Arc<WebServiceState<T>>>) -> impl Future {download::<T>}: Handler<axum::body::Body, _>` is not satisfied
  --> src/web/service.rs:45:20
   |
45 |             .serve(app.into_make_service())
   |                    ^^^^^^^^^^^^^^^^^^^^^^^ the trait `Handler<axum::body::Body, _>` is not implemented for `fn(axum::extract::Path<(std::string::String, std::string::String)>, Extension<Arc<WebServiceState<T>>>) -> impl Future {download::<T>}`
   |
   = note: required because of the requirements on the impl of `tower_service::Service<axum::http::Request<axum::body::Body>>` for `axum::handler::OnMethod<fn(axum::extract::Path<(std::string::String, std::string::String)>, Extension<Arc<WebServiceState<T>>>) -> impl Future {download::<T>}, axum::body::Body, _, EmptyRouter>`
   = note: 7 redundant requirements hidden
   = note: required because of the requirements on the impl of `tower_service::Service<axum::http::Request<axum::body::Body>>` for `Route<axum::handler::OnMethod<fn() -> impl Future {search_mirror}, axum::body::Body, (), EmptyRouter>, Route<axum::handler::OnMethod<fn() -> impl Future {search_registry}, axum::body::Body, (), EmptyRouter>, Route<axum::handler::OnMethod<fn(axum::extract::Path<std::string::String>) -> impl Future {remove_owner}, axum::body::Body, (axum::extract::Path<std::string::String>,), axum::handler::OnMethod<fn(axum::extract::Path<std::string::String>) -> impl Future {add_owner}, axum::body::Body, (axum::extract::Path<std::string::String>,), axum::handler::OnMethod<fn(axum::extract::Path<std::string::String>) -> impl Future {list_owners}, axum::body::Body, (axum::extract::Path<std::string::String>,), EmptyRouter>>>, Route<axum::handler::OnMethod<fn(axum::extract::Path<(std::string::String, std::string::String)>) -> impl Future {unyank}, axum::body::Body, (axum::extract::Path<(std::string::String, std::string::String)>,), EmptyRouter>, Route<axum::handler::OnMethod<fn(axum::extract::Path<(std::string::String, std::string::String)>) -> impl Future {yank}, axum::body::Body, (axum::extract::Path<(std::string::String, std::string::String)>,), EmptyRouter>, Route<axum::handler::OnMethod<fn() -> impl Future {publish}, axum::body::Body, (), EmptyRouter>, Route<axum::handler::OnMethod<fn(axum::extract::Path<(std::string::String, std::string::String)>, Extension<Arc<WebServiceState<T>>>) -> impl Future {download::<T>}, axum::body::Body, _, EmptyRouter>, EmptyRouter>>>>>>>`
   = note: required because of the requirements on the impl of `hyper::service::http::HttpService<axum::body::Body>` for `axum::routing::Layered<AddExtension<Route<axum::handler::OnMethod<fn() -> impl Future {search_mirror}, axum::body::Body, (), EmptyRouter>, Route<axum::handler::OnMethod<fn() -> impl Future {search_registry}, axum::body::Body, (), EmptyRouter>, Route<axum::handler::OnMethod<fn(axum::extract::Path<std::string::String>) -> impl Future {remove_owner}, axum::body::Body, (axum::extract::Path<std::string::String>,), axum::handler::OnMethod<fn(axum::extract::Path<std::string::String>) -> impl Future {add_owner}, axum::body::Body, (axum::extract::Path<std::string::String>,), axum::handler::OnMethod<fn(axum::extract::Path<std::string::String>) -> impl Future {list_owners}, axum::body::Body, (axum::extract::Path<std::string::String>,), EmptyRouter>>>, Route<axum::handler::OnMethod<fn(axum::extract::Path<(std::string::String, std::string::String)>) -> impl Future {unyank}, axum::body::Body, (axum::extract::Path<(std::string::String, std::string::String)>,), EmptyRouter>, Route<axum::handler::OnMethod<fn(axum::extract::Path<(std::string::String, std::string::String)>) -> impl Future {yank}, axum::body::Body, (axum::extract::Path<(std::string::String, std::string::String)>,), EmptyRouter>, Route<axum::handler::OnMethod<fn() -> impl Future {publish}, axum::body::Body, (), EmptyRouter>, Route<axum::handler::OnMethod<fn(axum::extract::Path<(std::string::String, std::string::String)>, Extension<Arc<WebServiceState<T>>>) -> impl Future {download::<T>}, axum::body::Body, _, EmptyRouter>, EmptyRouter>>>>>>>, Arc<WebServiceState<T>>>>`
   = note: required because of the requirements on the impl of `hyper::service::make::MakeServiceRef<hyper::server::tcp::addr_stream::AddrStream, axum::body::Body>` for `IntoMakeService<axum::routing::Layered<AddExtension<Route<axum::handler::OnMethod<fn() -> impl Future {search_mirror}, axum::body::Body, (), EmptyRouter>, Route<axum::handler::OnMethod<fn() -> impl Future {search_registry}, axum::body::Body, (), EmptyRouter>, Route<axum::handler::OnMethod<fn(axum::extract::Path<std::string::String>) -> impl Future {remove_owner}, axum::body::Body, (axum::extract::Path<std::string::String>,), axum::handler::OnMethod<fn(axum::extract::Path<std::string::String>) -> impl Future {add_owner}, axum::body::Body, (axum::extract::Path<std::string::String>,), axum::handler::OnMethod<fn(axum::extract::Path<std::string::String>) -> impl Future {list_owners}, axum::body::Body, (axum::extract::Path<std::string::String>,), EmptyRouter>>>, Route<axum::handler::OnMethod<fn(axum::extract::Path<(std::string::String, std::string::String)>) -> impl Future {unyank}, axum::body::Body, (axum::extract::Path<(std::string::String, std::string::String)>,), EmptyRouter>, Route<axum::handler::OnMethod<fn(axum::extract::Path<(std::string::String, std::string::String)>) -> impl Future {yank}, axum::body::Body, (axum::extract::Path<(std::string::String, std::string::String)>,), EmptyRouter>, Route<axum::handler::OnMethod<fn() -> impl Future {publish}, axum::body::Body, (), EmptyRouter>, Route<axum::handler::OnMethod<fn(axum::extract::Path<(std::string::String, std::string::String)>, Extension<Arc<WebServiceState<T>>>) -> impl Future {download::<T>}, axum::body::Body, _, EmptyRouter>, EmptyRouter>>>>>>>, Arc<WebServiceState<T>>>>>`
   

[cemoktra]

The thing is, that the generic worked before i made the await call

[davidpdrsn]

Turns it out its because surf::RequestBuilder::send returns a future that is !Sync. Specifically this

surf::get(format!(
    "https://crates.io/api/v1/crates/{}/{}/download",
    crate_name, crate_version
)).send()

That means the future your handler function returns is !Sync and axum currently requires all handler futures to be Sync. Its unclear if that is a requirement that can be lifted but would be good to investigate. I'm gonna file an issue on it.

I don't know of a workaround unfortunately. I'd recommend you ask in the tokio discord.

Update: Filed #329

[cemoktra]

So even if i'm not returning this future but trying to await it? The same happens when using reqwest instead of surf, also reqwest::blocking cannot be used as it will panic in async

[davidpdrsn]

Yes

[cemoktra]

I understand the problem with surf is due to surf using async-std while axum uses tokio. But i tried to replace surf with reqwest, which uses tokio (1.0) and i thought it might help. Since when the tokio future is Sync?

[cemoktra]

Maybe @seanmonstar can help me here?

[cemoktra]

Ok i'm using ureq which is not async now

[davidpdrsn]

Its easier if you add replies to posts instead of new comments.

But reqwest does work:

use axum::{extract::Extension, handler::get, http::StatusCode, AddExtensionLayer, Router};
use std::net::SocketAddr;

#[tokio::main]
async fn main() {
    let http_client = reqwest::Client::new();

    // build our application with a route
    let app = Router::new()
        .route("/", get(handler))
        .layer(AddExtensionLayer::new(http_client));

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

async fn handler(Extension(http_client): Extension<reqwest::Client>) -> Result<String, StatusCode> {
    let response = http_client
        .get("http://example.com")
        .send()
        .await
        .map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)?;

    let body = response
        .text()
        .await
        .map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)?;

    Ok(body)
}

[cemoktra]

I think i'm having the same problem again on this branch when trying to access S3:
https://github.com/cemoktra/cargolifter/tree/s3

How can i see if a Future is Send or Not? I mean aws sdk used tokio as async runtime too, why is it not working?

Should i implement channels for accessing S3 then?

[davidpdrsn]

I usually do this for checking if something is Send and/or Sync, assuming you cannot see it from the documentation.

fn check<T: Send + Sync>(t: T) -> T { t }

let some_future = foo();
let some_future = check(some_future); // this wont compile unless `some_future` is `Send + Sync`

Tokio is the runtime for executing futures and doesn't impact whether an individual future is Send + Sync or not.

If you need to share a value that isn't Send between threads then yes using channels is the way to go.