Tokio::spawn last woken time question

[Milo123459]

How do I make a tokio::spawn automatically "kill itself" after its last woken time was more than 60 seconds ago?

Suggestions appreciated!

[Darksonn]

This turns out to be rather tricky and requires a manual Future implementation. You can find one below. To use it, you would do tokio::spawn(PollTimeout::new(your_task, duration)).

use tokio::time::{sleep, Sleep, Duration, Instant};
use std::future::Future;
use std::pin::Pin;
use std::task::{Context, Poll};

pub struct PollTimeout<F> {
    future: F,
    sleep: Sleep,
    duration: Duration,
}

impl<F> PollTimeout<F> {
    pub fn new(future: F, duration: Duration) -> Self {
        Self {
            future,
            sleep: sleep(duration),
            duration,
        }
    }
}

impl<F: Future> Future for PollTimeout<F> {
    type Output = Result<F::Output, TimeoutError>;
    
    fn poll(self: Pin<&mut Self>, ctx: &mut Context<'_>) -> Poll<Result<F::Output, TimeoutError>> {
        let me = unsafe { Pin::into_inner_unchecked(self) };
        let mut sleep = unsafe { Pin::new_unchecked(&mut me.sleep) };
        let future = unsafe { Pin::new_unchecked(&mut me.future) };
        
        if sleep.as_mut().poll(ctx).is_ready() {
            return Poll::Ready(Err(TimeoutError {}));
        }
        sleep.reset(Instant::now() + me.duration);
        
        future.poll(ctx).map(Ok)
    }
}

struct TimeoutError {}

[Milo123459]

That looks rather confusing. Gonna give it a shot. 👍

[Milo123459]

Well, it works, @Darksonn but is there one without any unsafe? I really don't want to use unsafe.

[hawkw]

Well, it works, @Darksonn but is there one without any unsafe? I really don't want to use unsafe.

Try using pin-project

[Milo123459]

Yes, thank you!