https://without.boats/blog/why-async-rust/

Why async

Rust future中的三个概念:

An executor decides when and how to execute your futures.

Async trait & GAT

Pin&Self reference

Async runtime

let mut incoming = listener.incoming();
while let Some(stream) = incoming.next().await {
 // TODO
}

// 目前还不支持async的迭代器
for stream in listener.incoming() {}

fn main() -> Result<(), Box<dyn Error>> {
    let (_, bp) = backpressure::new(10);
    task::block_on(async {
        let listener = TcpListener::bind("localhost:8080").await?;
        eprintln!("Accepting connections on localhost:8080");
        let mut incoming = listener.incoming()
            .log_warnings(log_accept_error)
            .handle_errors(Duration::from_millis(500))
            .backpressure_wrapper(bp);
        while let Some(stream) = incoming.next().await {
            task::spawn(async {
                if let Err(e) = connection_loop(stream).await {
                    eprintln!("Error: {}", e);
                }
            });
        }
        Ok(())
    })
}

async fn connection_loop(mut stream: ByteStream) -> Result<(), io::Error> {
    println!("Connected from {}", stream.peer_addr()?);
    task::sleep(Duration::from_secs(5)).await;
    stream.write_all("hello\\n".as_bytes()).await?;
    Ok(())
}

fn log_accept_error(e: &io::Error) {
    eprintln!("Accept error: {}. Sleeping 0.5s. {}", e, error_hint(&e));
}