Documentation is at https://docs.rs/timed-queue .

lib.rs:

timed-queue provides TimedQueue, a set of objects and the minimum time at which they should be returned.

Example

Imagine the "new messages" queue of an SMTP server implementation. Delivery should be attempted immediately for new messages. Messages for which delivery fails should be retried after 30 minutes.

 fn server_loop<I: IntoIterator<Item = MailMessage>>(tq: TimedQueue<MailMessage>, messages: I) {
     for m in messages {
         tq.enqueue(m, None);
     }
 }

 async fn delivery_loop(tq: TimedQueue<MailMessage>) {
     loop {
         let (msg, _) = tq.dequeue().await;
         if try_deliver(msg).await.is_err() {
             tq.enqueue(msg, Some(Instant::now() + Duration::from_secs(30 * 60)));
         }
     }
 }

 #[tokio::main]
 async fn main() {
     let tq = TimedQueue::new();
     let tq2 = tq.clone();
     std::thread::spawn(move || server_loop(tq, get_message_stream()));
     tokio::spawn(delivery_loop(tq2));
 }