如何将这些引用传递给产生 tokio 任务的 function？

Question

我有一些完全按预期工作的代码：

pub async fn start(num_websockets: i32) {
    let messages_received = Arc::new(Mutex::new(0));
    let (shutdown_signal, _) = broadcast::channel(1);
    let (done, mut wait_for_tasks) = channel::<&str>(1);
    tokio::spawn(stats::message_counter(
        Arc::clone(&messages_received),
        shutdown_signal.subscribe(),
        done.clone(),
    ));
    for _i in 0..num_websockets {
        let (ws_stream, _) = websocket::connect().await.unwrap();
        let (mut write, read) = ws_stream.split();
        subscription::subscribe(&mut write, "book.BTC-PERPETUAL.100ms")
            .await
            .unwrap();
        tokio::spawn(websocket::listener(
            read,
            messages_received.clone(),
            shutdown_signal.subscribe(),
            done.clone(),
        ));
    }

在 for 循环中，我生成了任意数量的websocket::listener ，它会在接收到shutdown_signal时关闭，并通过done让main知道它们何时完成。

当我尝试将此代码提取到 function 时，如下所示：

...
    for _i in 0..num_websockets {
        subscribe_and_listen(messages_received.clone(), shutdown_signal.subscribe(), done.clone());
    }
...

async fn subscribe_and_listen(messages_received: Arc<Mutex<i32>>,
                              shutdown_signal: broadcast::Receiver<&str>,
                              done: mpsc::Sender<&str>) {
    let (ws_stream, _) = websocket::connect().await.unwrap();
    let (mut write, read) = ws_stream.split();
    subscription::subscribe(&mut write, "book.BTC-PERPETUAL.100ms")
        .await
        .unwrap();
    tokio::spawn(
        websocket::listener(
            read,
            messages_received.clone(),
            shutdown_signal,
            done.clone(),
        )
    );
}

编译器告诉我：

error[E0759]: `shutdown_signal` has an anonymous lifetime `'_` but it needs to satisfy a `'static` lifetime requirement
   --> src/benchmark.rs:21:9
    |
13  |                                 shutdown_signal: broadcast::Receiver<&str>,
    |                                                  ------------------------- this data with an anonymous lifetime `'_`...
...
21  | /         websocket::listener(
22  | |             read,
23  | |             messages_received.clone(),
24  | |             shutdown_signal,
    | |             --------------- ...is used here...
25  | |             done.clone(),
26  | |         )
    | |_________^
    |
note: ...and is required to live as long as `'static` here
   --> src/benchmark.rs:20:5
    |
20  |     tokio::spawn(
    |     ^^^^^^^^^^^^
note: `'static` lifetime requirement introduced by this bound
   --> /Users/b0nes/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-1.20.0/src/task/spawn.rs:127:28
    |
127 |         T: Future + Send + 'static,

我尝试了很多东西，但我根本无法将这段代码移动到 function，我真的很想了解如何做到这一点。 在我看来，不需要任何东西是'static ，因为 function 可以完全拥有shutdown_signal.subscribe()和done.clone()的结果

Answer 1

解决方案是为通道shutdown_signal和done使用String ，或者使用其他满足 'static 的类型，例如 &'static str。

在我的情况下，我实际上不需要提供任何字符串，所以我只是用()创建了一个频道。

问题是， &str不能被拥有，但这正是tokio::spawn任务所需要的。