一、使用async搭建简单的web服务

1、修改cargo.toml文件添加依赖

[dependencies]
futures = "0.3"
tokio = { version = "1", features = ["full"] }
[dependencies.async-std]
version = "1.6"
features = ["attributes"]

2、搭建web服务

（1）单线程并发处理请求

这里解释一下，单线程并发处理请求，其实每一个请求都是一个future，如果一个future卡了，会去处理别的future，async原理可以去看我关于async的博客

use async_std::net::TcpListener;
use async_std::net::TcpStream;
use futures::stream::StreamExt;use std::fs;
use async_std::prelude::*;
use std::time::Duration;
use async_std::task;#[async_std::main]
async fn main() {let listener = TcpListener::bind("127.0.0.1:7878").await.unwrap(); // 创建 TCP 监听器，绑定到本地 7878 端口listener.incoming() // 监听传入的连接.for_each_concurrent(/* limit */ None, |tcpstream| async move {//stream 流异步并发处理let tcpstream = tcpstream.unwrap(); // 获取传入连接handle_connection(tcpstream).await; // 处理连接的异步任务}).await; // 等待所有连接处理完毕
}async fn handle_connection(mut stream: TcpStream) {let mut buffer = [0; 1024];stream.read(&mut buffer).await.unwrap(); // 读取 TCP 流数据到缓冲区let get = b"GET / HTTP/1.1\r\n";let sleep = b"GET /sleep HTTP/1.1\r\n";// 判断请求内容，确定响应状态行和文件名let (status_line, filename) = if buffer.starts_with(get) {("HTTP/1.1 200 OK\r\n\r\n", "hello.html") // 如果请求是 GET /，返回 200 OK 状态和 hello.html 文件} else if buffer.starts_with(sleep) {task::sleep(Duration::from_secs(5)).await; // 如果请求是 GET /sleep，等待 5 秒钟("HTTP/1.1 200 OK\r\n\r\n", "hello.html") // 然后返回 200 OK 状态和 hello.html 文件} else {("HTTP/1.1 404 NOT FOUND\r\n\r\n", "404.html") // 其他情况返回 404 NOT FOUND 状态和 404.html 文件};// 读取文件内容到字符串let contents = fs::read_to_string(filename).unwrap();let response = format!("{status_line}{contents}"); // 构建响应字符串// 将响应字符串写入 TCP 流，并刷新stream.write(response.as_bytes()).await.unwrap();stream.flush().await.unwrap();
}

（2）多线程并发处理请求

lib.rs

// src/lib.rs
use std::{sync::{mpsc, Arc, Mutex},thread,
};pub struct ThreadPool {workers: Vec<Worker>,sender: Option<mpsc::Sender<Job>>,
}type Job = Box<dyn FnOnce() + Send + 'static>;impl ThreadPool {/// Create a new ThreadPool.////// The size is the number of threads in the pool.////// # Panics////// The `new` function will panic if the size is zero.pub fn new(size: usize) -> ThreadPool {assert!(size > 0);let (sender, receiver) = mpsc::channel();let receiver = Arc::new(Mutex::new(receiver));let mut workers = Vec::with_capacity(size);for id in 0..size {workers.push(Worker::new(id, Arc::clone(&receiver)));}ThreadPool {workers,sender: Some(sender),}}pub fn execute<F>(&self, f: F)whereF: FnOnce() + Send + 'static,{let job = Box::new(f);self.sender.as_ref().unwrap().send(job).unwrap();}
}impl Drop for ThreadPool {fn drop(&mut self) {drop(self.sender.take());for worker in &mut self.workers {println!("Shutting down worker {}", worker.id);if let Some(thread) = worker.thread.take() {thread.join().unwrap();}}}
}struct Worker {id: usize,thread: Option<thread::JoinHandle<()>>,
}impl Worker {fn new(id: usize, receiver: Arc<Mutex<mpsc::Receiver<Job>>>) -> Worker {let thread = thread::spawn(move || loop {let message = receiver.lock().unwrap().recv();match message {Ok(job) => {println!("Worker {id} got a job; executing.");job();}Err(_) => {println!("Worker {id} disconnected; shutting down.");break;}}});Worker {id,thread: Some(thread),}}
}

main.rs

// src/main.rs
use hello_package::ThreadPool;
use std::fs;
use std::io::prelude::*;
use std::net::TcpListener;
use std::net::TcpStream;
use std::thread;
use std::time::Duration;fn main() {let listener = TcpListener::bind("127.0.0.1:7878").unwrap();let pool = ThreadPool::new(4);for stream in listener.incoming().take(4) {//take限制请求次数let stream = stream.unwrap();pool.execute(|| {handle_connection(stream);});}println!("Shutting down.");
}fn handle_connection(mut stream: TcpStream) {let mut buffer = [0; 1024];stream.read(&mut buffer).unwrap();let get = b"GET / HTTP/1.1\r\n";let sleep = b"GET /sleep HTTP/1.1\r\n";let (status_line, filename) = if buffer.starts_with(get) {("HTTP/1.1 200 OK", "hello.html")} else if buffer.starts_with(sleep) {thread::sleep(Duration::from_secs(5));("HTTP/1.1 200 OK", "hello.html")} else {("HTTP/1.1 404 NOT FOUND", "404.html")};let contents = fs::read_to_string(filename).unwrap();let response = format!("{}\r\nContent-Length: {}\r\n\r\n{}",status_line,contents.len(),contents);stream.write_all(response.as_bytes()).unwrap();stream.flush().unwrap();
}