Rust为线程或函数创建超时的正确方法是什么？

Question

这是我的代码:

use std::net;
use std::thread;
extern crate argparse;
use argparse::{ArgumentParser, StoreTrue, Store};

fn scan_port(host: &str, port: u16) -> bool {
    let host = host.to_string();
    let port = port;
    let t = thread::spawn(move || net::TcpStream::connect((host.as_str(), port)).is_ok());

    t.join().unwrap()
}

如果连接未在N秒内完成,如何创建线程将被终止或终止的情况？

所有这一切的原因是Rust无法设置套接字连接超时,因此我无法确保程序不会卡住.

Answer 1

正如@Shepmaster所说:终止线程是个坏主意.

你可以做的是给线程一个Sender它应该通知你,如果它已成功打开一个连接(甚至可能通过发送你的句柄).然后你可以让你的主线程sleep等待你想要的时间.当你的线程被唤醒时,它会Receiver从线程中检查其对应的生命迹象.如果线程没有回答,只是通过降低释放到野外JoinHandle和Receiver.它不像消耗cpu时间(它被阻止),而且它不会消耗太多内存.如果它解锁,它将检测到它Sender没有连接并且可以关闭.

当然你不应该有这些开放线程的bazillions,因为它们仍然使用资源(内存和系统线程句柄),但在正常的系统上,这不是一个问题.

例:

use std::net;
use std::thread;
use std::sync::mpsc;

fn scan_port(host: &str, port: u16) -> bool {
    let host = host.to_string();
    let port = port;
    let (sender, receiver) = mpsc::channel();
    let t = thread::spawn(move || {
        match sender.send(net::TcpStream::connect((host.as_str(), port))) {
            Ok(()) => {}, // everything good
            Err(_) => {}, // we have been released, don't panic
        }
    });

    thread::sleep(std::time::Duration::new(5, 0));

    match receiver.try_recv() {
        Ok(Ok(handle)) => true, // we have a connection
        Ok(Err(_)) => false, // connecting failed
        Err(mpsc::TryRecvError::Empty) => {
            drop(receiver);
            drop(t);
            // connecting took more than 5 seconds
            false
        },
        Err(mpsc::TryRecvError::Disconnected) => unreachable!(),
    }
}

Answer 2

@ker 的回答将始终等待 5 秒，即使连接完成得更快。这是一种类似的方法，超时和网络请求都发生在不同的线程上，第一个完成的获胜：

let (sender, receiver) = mpsc::channel();
let tsender = sender.clone();
let t = thread::spawn(move || {
    match sender.send(Ok(net::TcpStream::connect((host.as_str(), port)))) {
        Ok(()) => {}, // everything good
        Err(_) => {}, // we have been released, don't panic
    }
});
let timer = thread::spawn(move || {
  thread::sleep(Duration::from_millis(5000));
  match tsender.send(Err(MyTimeoutError)) {
    Ok(()) => {}, // oops, we timed out
    Err(_) => {}, // great, the request finished already
  }
});
return receiver.recv().unwrap();

但只要你这样做，你不妨recv_timeout改为使用：

let (sender, receiver) = mpsc::channel();
let t = thread::spawn(move || {
    match sender.send(net::TcpStream::connect((host.as_str(), port))) {
        Ok(()) => {}, // everything good
        Err(_) => {}, // we have been released, don't panic
    }
});
return receiver.recv_timeout(Duration::from_millis(5000));