Function fibers::sync::oneshot::monitor

pub fn monitor<T, E>() -> (Monitored<T, E>, Monitor<T, E>)

Creates a oneshot channel for unidirectional monitoring.

When Monitored object is (intentionally or unintentionally) dropped, the corresponding Monitor object will detect it and return the resulting value at the next time the Future::poll method is called on it.

Examples

An example of monitoring a successful completion:

use fibers::{Executor, InPlaceExecutor, Spawn};
use fibers::sync::oneshot;
use futures::{Async, Future};

let mut executor = InPlaceExecutor::new().unwrap();
let (monitored, mut monitor) = oneshot::monitor();

// Spawns monitored fiber
// (In practice, spawning fiber via `spawn_monitor` function is
//  more convenient way to archieve the same result)
executor.spawn_fn(move || {
    // Notifies the execution have completed successfully.
    monitored.exit(Ok("succeeded") as Result<_, ()>);
    Ok(())
});

// Runs `executor` until above fiber exists
loop {
    let result = monitor.poll().expect("Unexpected failure");
    if let Async::Ready(value) = result {
        assert_eq!(value, "succeeded");
        break;
    } else {
        executor.run_once().unwrap();
    }
}

An example of detecting unintentional termination:

use fibers::{Executor, InPlaceExecutor, Spawn};
use fibers::sync::oneshot;
use futures::{Async, Future};

let mut executor = InPlaceExecutor::new().unwrap();
let (monitored, mut monitor) = oneshot::monitor::<(),()>();

// Spawns monitored fiber
// (In practice, spawning fiber via `spawn_monitor` function is
//  more convenient way to archieve the same result)
executor.spawn_fn(move || {
    let _ = monitored; // This fiber owns `monitored`
    Ok(()) // Terminated before calling `Monitored::exit` method
});

// Runs `executor` until above fiber exists
loop {
    match monitor.poll() {
        Ok(Async::NotReady) => {
            executor.run_once().unwrap();
        }
        Ok(Async::Ready(_)) => unreachable!(),
        Err(e) => {
            assert_eq!(e, oneshot::MonitorError::Aborted);
            break;
        }
    }
}

Implementation Details

Internally, this channel is almost the same as the one created by channel function.