Asynchronous delay queue

A queue of delayed elements backed by futures-timer that can be used with both

• async-std as default, and
• tokio with feature "use-tokio"

An element is inserted into the [DelayQueue] and will be yielded once the specified deadline has been reached.

The delayed items can be consumed through a channel returned at creation.

Implementation

The delays are spawned and a timeout races against a reset channel that can be triggered with the DelayHandle. If the timeout occurs before cancelation or a reset the item is yielded through the receiver channel.

Usage

Elements are inserted into [DelayQueue] using the [DelayQueue::insert] or [DelayQueue::insert_at] methods. A deadline is provided with the item and a DelayHandle is returned. The delay handle is used to remove the entry.

The delays can be configured with the [DelayHandle::reset_at] or the [DelayHandle::reset] method or canceled by calling the [DelayHandle::cancel] method. Dropping the handle will not cancel the delay.

Modification of the delay fails if the delayed item expired in the meantime. In this case an [ErrorAlreadyExpired] will be returned. If modification succeeds the handle will be returned back to the caller.

Example

use futures_delay_queue::delay_queue;
use std::time::Duration;

#[async_std::main]
async fn main() {
    let (delay_queue, rx) = delay_queue::<i32>(3);

    let delay_handle = delay_queue.insert(1, Duration::from_millis(20));
    assert!(delay_handle.reset(Duration::from_millis(40)).await.is_ok());

    let delay_handle = delay_queue.insert(2, Duration::from_millis(10));
    assert!(delay_handle.cancel().await.is_ok());

    let delay_handle = delay_queue.insert(3, Duration::from_millis(30));

    assert_eq!(rx.receive().await, Some(3));
    assert_eq!(rx.receive().await, Some(1));

    drop(delay_queue);
    assert_eq!(rx.receive().await, None);
}