try_recv_many()

demo.rs

    fn amain() {
        use std::{
            future::poll_fn,
            pin::Pin,
            task::{Context, Poll},
        };

        use tokio::sync::mpsc;
        let (tx, mut rx) = mpsc::channel(100);

        // Spawn a thread to send messages
        std::thread::spawn(move || {
            let runtime = tokio::runtime::Runtime::new().unwrap();
            runtime.block_on(async move {
                tx.send(1).await.unwrap();
                tx.send(2).await.unwrap();
                tx.send(3).await.unwrap();
            });
        });

        // Use poll_fn to read messages from the receiver
        let mut buffer = Vec::new();
        let limit = 10;
        let future = poll_fn(move |cx: &mut Context<'_>| {
            match Pin::new(&mut rx).poll_recv_many(cx, &mut buffer, limit) {
                Poll::Ready(count) => {
                    println!("Received {} messages", count);
                    Poll::Ready(())
                }
                Poll::Pending => Poll::Pending,
            }
        });

        // Run the future to completion
        let runtime = tokio::runtime::Runtime::new().unwrap();
        runtime.block_on(future);

        // Print the received messages
        // println!("Received messages: {:?}", buffer);
    }

    fn read_items(mut rx: tokio::sync::mpsc::Receiver<String>) {
        use std::task::{Context, Poll};
        let waker = futures_util::task::noop_waker();
        let mut cx = Context::from_waker(&waker);

        let mut items = Vec::with_capacity(10);
        loop {
            match rx.poll_recv_many(&mut cx, &mut items, 10) {
                Poll::Ready(0) => {
                    println!("Channel closed, no more items");
                    break;
                }
                Poll::Ready(n) => {
                    println!("Received {} items: {:?}", n, &items[..n]);
                    items.clear();
                }
                Poll::Pending => {
                    println!("No items available, waiting...");
                }
            }
        }
    }