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task canceled when client connection closed #2728

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polariseye opened this issue Dec 29, 2021 · 4 comments
Closed

task canceled when client connection closed #2728

polariseye opened this issue Dec 29, 2021 · 4 comments
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C-bug Category: bug. Something is wrong. This is bad!

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@polariseye
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polariseye commented Dec 29, 2021 •
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Version
hyper 0.14.16

Platform
windows

Description
the task was canceled when the http connection closed
One way to structure the description:

[short summary of the bug]
task canceled when client connection closed.
I tried this code:

async fn hello_world(_req: Request<Body>) -> Result<Response<Body>, Infallible> {
    println!("start sleep!!!!!");
    tokio::time::sleep(tokio::time::Duration::from_secs(20)).await;
    println!("end sleep!!!!");
    Ok(Response::new("Hello, World".into()))
}

#[tokio::main]
async fn main() {
    // We'll bind to 127.0.0.1:3000
    let addr = SocketAddr::from(([127, 0, 0, 1], 3000));

    // A `Service` is needed for every connection, so this
    // creates one from our `hello_world` function.
    let make_svc = make_service_fn(|_conn| async {
        // service_fn converts our function into a `Service`
        Ok::<_, Infallible>(service_fn(hello_world))
    });

    let server = Server::bind(&addr).serve(make_svc);

    // Run this server for... forever!
    if let Err(e) = server.await {
        eprintln!("server error: {}", e);
    }
}

[code sample that causes the bug]
i tried curl --location --request POST 'http://127.0.0.1:3030'.and then, abort request. the server side just print "start sleep!!!!!".not print "end sleep!!!!"
I expected to see this happen: [explanation]
i want to see print "end sleep!!!!"
Instead, this happened: [explanation]
@polariseye polariseye added the C-bug Category: bug. Something is wrong. This is bad! label Dec 29, 2021
@seanmonstar
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This is expected behavior. When the connection closes, the relevant task is canceled.

@polariseye
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well~~could you please tell me how can i let the task will not cancel

@seanmonstar
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You can't make prevent that specific task from being canceled. But, depending on what you're actually trying to do, you have a few options:

  • If you just want to make sure something definitely happens, like cleaning up a resource or logging, you could create a custom type and impl Drop for it, and then let _guard = MyGuard;.
  • You could move the handler code into a task::spawn, which doesn't cancel normally, and have that spawned task return a Response. Something like: 
    async fn hello(req: Request) -> Result {
    tokio::spawn(async move {
        do_stuff(req).await;
        Ok(resp)
    }).await
}

@polariseye
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that's good.thank you very mutch

@davepacheco davepacheco mentioned this issue Jun 12, 2023
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@seanmonstar @polariseye