Rust编程语言入门之最后的项目：多线程 Web 服务器

最后的项目：多线程 Web 服务器

构建多线程 Web 服务器

• 在 socket 上监听 TCP 连接
• 解析少量的 HTTP 请求
• 创建一个合适的 HTTP 响应
• 使用线程池改进服务器的吞吐量
• 优雅的停机和清理
• 注意：并不是最佳实践

创建项目

~/rust
➜ cargo new hello
     Created binary (application) `hello` package

~/rust
➜

main.rs 文件

use std::net::TcpListener;

fn main() {
    let listener = TcpListener::bind("127.0.0.1:7878").unwrap();
    for stream in listener.incoming() {
        let stream = stream.unwrap();

        println!("Connection established!");
    }
}

修改一：

use std::io::prelude::*;
use std::net::TcpListener;
use std::net::TcpStream;

fn main() {
    let listener = TcpListener::bind("127.0.0.1:7878").unwrap();
    for stream in listener.incoming() {
        let stream = stream.unwrap();

        handle_connection(stream);
    }
}

fn handle_connection(mut stream: TcpStream) {
    let mut buffer = [0; 512];

    stream.read(&mut buffer).unwrap();

    println!("Request: {}", String::from_utf8_lossy(&buffer[..]));
}

修改二：

use std::io::prelude::*;
use std::net::TcpListener;
use std::net::TcpStream;

fn main() {
    let listener = TcpListener::bind("127.0.0.1:7878").unwrap();
    for stream in listener.incoming() {
        let stream = stream.unwrap();

        handle_connection(stream);
    }
}

fn handle_connection(mut stream: TcpStream) {
    let mut buffer = [0; 512];

    stream.read(&mut buffer).unwrap();

    // 请求
    // Method Request-URI HTTP-Version CRLF
    // headers CRLF
    // message-body

    // 响应
    // HTTP-Version Status-Code Reason-Phrase CRLF
    // headers CRLF
    // message-body

    let response = "HTTP/1.1 200 OK\r\n\r\n";

    stream.write(response.as_bytes()).unwrap();
    stream.flush().unwrap();

    println!("Request: {}", String::from_utf8_lossy(&buffer[..]));
}

修改三：

use std::fs;
use std::io::prelude::*;
use std::net::TcpListener;
use std::net::TcpStream;

fn main() {
    let listener = TcpListener::bind("127.0.0.1:7878").unwrap();
    for stream in listener.incoming() {
        let stream = stream.unwrap();

        handle_connection(stream);
    }
}

fn handle_connection(mut stream: TcpStream) {
    let mut buffer = [0; 512];

    stream.read(&mut buffer).unwrap();

    // 请求
    // Method Request-URI HTTP-Version CRLF
    // headers CRLF
    // message-body

    // 响应
    // HTTP-Version Status-Code Reason-Phrase CRLF
    // headers CRLF
    // message-body

    let contents = fs::read_to_string("hello.html").unwrap();
    let response = format!("HTTP/1.1 200 OK\r\n\r\n{}", contents);

    stream.write(response.as_bytes()).unwrap();
    stream.flush().unwrap();
}

修改四：

use std::fs;
use std::io::prelude::*;
use std::net::TcpListener;
use std::net::TcpStream;

fn main() {
    let listener = TcpListener::bind("127.0.0.1:7878").unwrap();
    for stream in listener.incoming() {
        let stream = stream.unwrap();

        handle_connection(stream);
    }
}

fn handle_connection(mut stream: TcpStream) {
    let mut buffer = [0; 512];

    stream.read(&mut buffer).unwrap();

    let get = b"GET / HTTP/1.1\r\n";

    if buffer.starts_with(get) {
        let contents = fs::read_to_string("hello.html").unwrap();
        let response = format!("HTTP/1.1 200 OK\r\n\r\n{}", contents);

        stream.write(response.as_bytes()).unwrap();
        stream.flush().unwrap();
    } else {
        let status_line = "HTTP/1.1 404 NOT FOUND\r\n\r\n";
        let contents = fs::read_to_string("404.html").unwrap();

        let response = format!("{}{}", status_line, contents);

        stream.write(response.as_bytes()).unwrap();
        stream.flush().unwrap();
    }
}

修改五：

use std::fs;
use std::io::prelude::*;
use std::net::TcpListener;
use std::net::TcpStream;

fn main() {
    let listener = TcpListener::bind("127.0.0.1:7878").unwrap();
    for stream in listener.incoming() {
        let stream = stream.unwrap();

        handle_connection(stream);
    }
}

fn handle_connection(mut stream: TcpStream) {
    let mut buffer = [0; 512];

    stream.read(&mut buffer).unwrap();

    let get = b"GET / HTTP/1.1\r\n";

    let (status_line, filename) = if buffer.starts_with(get) {
        ("HTTP/1.1 200 OK\r\n\r\n", "hello.html")
    } else {
        ("HTTP/1.1 404 NOT FOUND\r\n\r\n", "404.html")
    };

    let contents = fs::read_to_string(filename).unwrap();

    let response = format!("{}{}", status_line, contents);

    stream.write(response.as_bytes()).unwrap();
    stream.flush().unwrap();
}

hello.html 文件

<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="utf-8">
        <title>Hello</title>
    </head>

    <body>
        <h1>Hello</h1>
        <p>Hi from Rust</p>
    </body>
</html>

404.html 文件

<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="utf-8">
        <title>Hello!</title>
    </head>
    <body>
        <h1>Oops!</h1>
        <p>Sorry, I don't know what you're asking for.</p>
    </body>
</html>

单线程Web服务器

use std::fs;
use std::thread;
use std::io::prelude::*;
use std::net::TcpListener;
use std::net::TcpStream;
use std::time::Duration;

fn main() {
    let listener = TcpListener::bind("127.0.0.1:7878").unwrap();
    for stream in listener.incoming() {
        let stream = stream.unwrap();

        handle_connection(stream);
    }
}

fn handle_connection(mut stream: TcpStream) {
    let mut buffer = [0; 512];

    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\r\n\r\n", "hello.html")
    } else if buffer.starts_with(sleep) {
        thread::sleep(Duration::from_secs(5));
        ("HTTP/1.1 200 OK\r\n\r\n", "hello.html")
    } else {
        ("HTTP/1.1 404 NOT FOUND\r\n\r\n", "404.html")
    };

    let contents = fs::read_to_string(filename).unwrap();

    let response = format!("{}{}", status_line, contents);

    stream.write(response.as_bytes()).unwrap();
    stream.flush().unwrap();
}

开启线程

use std::fs;
use std::thread;
use std::io::prelude::*;
use std::net::TcpListener;
use std::net::TcpStream;
use std::time::Duration;

fn main() {
    let listener = TcpListener::bind("localhost:7878").unwrap();
    for stream in listener.incoming() {
        let stream = stream.unwrap();

        thread::spawn(|| {
            handle_connection(stream);
        });
    }
}

fn handle_connection(mut stream: TcpStream) {
    let mut buffer = [0; 512];

    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\r\n\r\n", "hello.html")
    } else if buffer.starts_with(sleep) {
        thread::sleep(Duration::from_secs(5));
        ("HTTP/1.1 200 OK\r\n\r\n", "hello.html")
    } else {
        ("HTTP/1.1 404 NOT FOUND\r\n\r\n", "404.html")
    };

    let contents = fs::read_to_string(filename).unwrap();

    let response = format!("{}{}", status_line, contents);

    stream.write(response.as_bytes()).unwrap();
    stream.flush().unwrap();
}

lib.rs 文件

use std::thread;

pub struct ThreadPool {
    threads: Vec<thread::JoinHandle<()>>,
}

impl ThreadPool {
    /// Creates 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 mut threads = Vec::with_capacity(size);

        for _ in 0..size {
            // create some threads and store them in the vector
        }
        ThreadPool { threads }
    }

    pub fn execute<F>(&self, f: F)
    where
        F: FnOnce() + Send + 'static,
    {
    }
}

lib.rs 修改一

use std::thread;

pub struct ThreadPool {
    workers: Vec<Worker>,
}

impl ThreadPool {
    /// Creates 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 mut workers = Vec::with_capacity(size);

        for id in 0..size {
            workers.push(Worker::new(id));
        }
        ThreadPool { workers }
    }

    pub fn execute<F>(&self, f: F)
    where
        F: FnOnce() + Send + 'static,
    {
    }
}

struct Worker {
    id: usize,
    thread: thread::JoinHandle<()>,
}

impl Worker {
    fn new(id: usize) -> Worker {
        let thread = thread::spawn(|| {});

        Worker { id, thread }
    }
}

lib.rs 修改二

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

pub struct ThreadPool {
    workers: Vec<Worker>,
    sender: mpsc::Sender<Job>,
}

struct Job;
impl ThreadPool {
    /// Creates 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 mut workers = Vec::with_capacity(size);

        for id in 0..size {
            workers.push(Worker::new(id, receiver));
        }
        ThreadPool { workers, sender }
    }

    pub fn execute<F>(&self, f: F)
    where
        F: FnOnce() + Send + 'static,
    {
    }
}

struct Worker {
    id: usize,
    thread: thread::JoinHandle<()>,
}

impl Worker {
    fn new(id: usize, receiver: mpsc::Receiver<Job>) -> Worker {
        let thread = thread::spawn(|| {
            receiver;
        });

        Worker { id, thread }
    }
}

lib.rs 修改三

use std::thread;
use std::sync::mpsc;
use std::sync::Arc;
use std::sync::Mutex;

pub struct ThreadPool {
    workers: Vec<Worker>,
    sender: mpsc::Sender<Job>,
}

struct Job;
impl ThreadPool {
    /// Creates 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 }
    }

    pub fn execute<F>(&self, f: F)
    where
        F: FnOnce() + Send + 'static,
    {
    }
}

struct Worker {
    id: usize,
    thread: thread::JoinHandle<()>,
}

impl Worker {
    fn new(id: usize, receiver: Arc<Mutex<mpsc::Receiver<Job>>>) -> Worker {
        let thread = thread::spawn(|| {
            receiver;
        });

        Worker { id, thread }
    }
}

lib.rs 修改四

use std::thread;
use std::sync::mpsc;
use std::sync::Arc;
use std::sync::Mutex;

pub struct ThreadPool {
    workers: Vec<Worker>,
    sender: mpsc::Sender<Job>,
}

// struct Job;
type Job = Box<FnOnce() + Send + 'static>;
impl ThreadPool {
    /// Creates 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 }
    }

    pub fn execute<F>(&self, f: F)
    where
        F: FnOnce() + Send + 'static,
    {
        let job = Box::new(f);
        self.sender.send(job).unwrap();
    }
}

struct Worker {
    id: usize,
    thread: thread::JoinHandle<()>,
}

impl Worker {
    fn new(id: usize, receiver: Arc<Mutex<mpsc::Receiver<Job>>>) -> Worker {
        let thread = thread::spawn(move || loop {
            let job = receiver.lock().unwrap().recv().unwrap();

            println!("Worker {} got a job; executing.", id);

            (*job)();
        });

        Worker { id, thread }
    }
}

lib.rs 修改五

use std::thread;
use std::sync::mpsc;
use std::sync::Arc;
use std::sync::Mutex;

pub struct ThreadPool {
    workers: Vec<Worker>,
    sender: mpsc::Sender<Job>,
}

// struct Job;
// type Job = Box<FnOnce() + Send + 'static>;
impl ThreadPool {
    /// Creates 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 }
    }

    pub fn execute<F>(&self, f: F)
    where
        F: FnOnce() + Send + 'static,
    {
        let job = Box::new(f);
        self.sender.send(job).unwrap();
    }
}

struct Worker {
    id: usize,
    thread: thread::JoinHandle<()>,
}

trait FnBox {
    fn call_box(self: Box<Self>);
}

impl<F: FnOnce()> FnBox for F {
    fn call_box(self: Box<F>) {
        (*self)()
    }
}

type Job = Box<dyn FnBox + Send + 'static>;

impl Worker {
    fn new(id: usize, receiver: Arc<Mutex<mpsc::Receiver<Job>>>) -> Worker {
        let thread = thread::spawn(move || loop {
            let job = receiver.lock().unwrap().recv().unwrap();

            println!("Worker {} got a job; executing.", id);

            // (*job)();
            job.call_box();
        });

        Worker { id, thread }
    }
}

lib.rs 修改六

use std::sync::mpsc;
use std::sync::Arc;
use std::sync::Mutex;
use std::thread;

pub struct ThreadPool {
    workers: Vec<Worker>,
    sender: mpsc::Sender<Job>,
}

// struct Job;
// type Job = Box<FnOnce() + Send + 'static>;
impl ThreadPool {
    /// Creates 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 }
    }

    pub fn execute<F>(&self, f: F)
    where
        F: FnOnce() + Send + 'static,
    {
        let job = Box::new(f);
        self.sender.send(job).unwrap();
    }
}

struct Worker {
    id: usize,
    thread: thread::JoinHandle<()>,
}

trait FnBox {
    fn call_box(self: Box<Self>);
}

impl<F: FnOnce()> FnBox for F {
    fn call_box(self: Box<F>) {
        (*self)()
    }
}

type Job = Box<dyn FnBox + Send + 'static>;

impl Worker {
    fn new(id: usize, receiver: Arc<Mutex<mpsc::Receiver<Job>>>) -> Worker {
        let thread = thread::spawn(move || loop {
            while let Ok(job) = receiver.lock().unwrap().recv() {
                println!("Worker {} got a job; executing.", id);

                job.call_box();
            }
        });

        Worker { id, thread }
    }
}

优雅的停机和清理

use std::sync::mpsc;
use std::sync::Arc;
use std::sync::Mutex;
use std::thread;

pub struct ThreadPool {
    workers: Vec<Worker>,
    sender: mpsc::Sender<Job>,
}

// struct Job;
// type Job = Box<FnOnce() + Send + 'static>;
impl ThreadPool {
    /// Creates 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 }
    }

    pub fn execute<F>(&self, f: F)
    where
        F: FnOnce() + Send + 'static,
    {
        let job = Box::new(f);
        self.sender.send(job).unwrap();
    }
}

impl Drop for ThreadPool {
    fn drop(&mut self) {
        for worker in &mut self.workers {
            println!("Shutting down worker {}", worker.id);

            worker.thread.join().unwrap()
        }
    }
}

struct Worker {
    id: usize,
    thread: thread::JoinHandle<()>,
}

trait FnBox {
    fn call_box(self: Box<Self>);
}

impl<F: FnOnce()> FnBox for F {
    fn call_box(self: Box<F>) {
        (*self)()
    }
}

type Job = Box<dyn FnBox + Send + 'static>;

impl Worker {
    fn new(id: usize, receiver: Arc<Mutex<mpsc::Receiver<Job>>>) -> Worker {
        let thread = thread::spawn(move || loop {
            while let Ok(job) = receiver.lock().unwrap().recv() {
                println!("Worker {} got a job; executing.", id);

                job.call_box();
            }
        });

        Worker { id, thread }
    }
}

修改优化一：

use std::sync::mpsc;
use std::sync::Arc;
use std::sync::Mutex;
use std::thread;

pub struct ThreadPool {
    workers: Vec<Worker>,
    sender: mpsc::Sender<Job>,
}

// struct Job;
// type Job = Box<FnOnce() + Send + 'static>;
impl ThreadPool {
    /// Creates 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 }
    }

    pub fn execute<F>(&self, f: F)
    where
        F: FnOnce() + Send + 'static,
    {
        let job = Box::new(f);
        self.sender.send(job).unwrap();
    }
}

impl Drop for ThreadPool {
    fn drop(&mut self) {
        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<()>>,
}

trait FnBox {
    fn call_box(self: Box<Self>);
}

impl<F: FnOnce()> FnBox for F {
    fn call_box(self: Box<F>) {
        (*self)()
    }
}

type Job = Box<dyn FnBox + Send + 'static>;

impl Worker {
    fn new(id: usize, receiver: Arc<Mutex<mpsc::Receiver<Job>>>) -> Worker {
        let thread = thread::spawn(move || loop {
            while let Ok(job) = receiver.lock().unwrap().recv() {
                println!("Worker {} got a job; executing.", id);

                job.call_box();
            }
        });

        Worker {
            id,
            thread: Some(thread),
        }
    }
}

最终版 lib.rs 文件

use std::sync::mpsc;
use std::sync::Arc;
use std::sync::Mutex;
use std::thread;

enum Message {
    NewJob(Job),
    Terminate,
}

pub struct ThreadPool {
    workers: Vec<Worker>,
    sender: mpsc::Sender<Message>,
}

// struct Job;
// type Job = Box<FnOnce() + Send + 'static>;
impl ThreadPool {
    /// Creates 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 }
    }

    pub fn execute<F>(&self, f: F)
    where
        F: FnOnce() + Send + 'static,
    {
        let job = Box::new(f);
        self.sender.send(Message::NewJob(job)).unwrap();
    }
}

impl Drop for ThreadPool {
    fn drop(&mut self) {
        println!("Sending terminate message to all workers.");

        for _ in &mut self.workers {
            self.sender.send(Message::Terminate).unwrap();
        }
        println!("Shutting down all workers.");
        
        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<()>>,
}

trait FnBox {
    fn call_box(self: Box<Self>);
}

impl<F: FnOnce()> FnBox for F {
    fn call_box(self: Box<F>) {
        (*self)()
    }
}

type Job = Box<dyn FnBox + Send + 'static>;

impl Worker {
    fn new(id: usize, receiver: Arc<Mutex<mpsc::Receiver<Message>>>) -> Worker {
        let thread = thread::spawn(move || loop {
            let message = receiver.lock().unwrap().recv().unwrap();
            match message {
                Message::NewJob(job) => {
                    println!("Worker {} got a job; executing.", id);
                    job.call_box();
                }
                Message::Terminate => {
                    println!("Worker {} got a job; executing.", id);
                    break;
                }
            }
        });

        Worker {
            id,
            thread: Some(thread),
        }
    }
}

最终版 main.rs 文件

use hello::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("localhost:7878").unwrap();
    let pool = ThreadPool::new(4);
    for stream in listener.incoming().take(2) {
        let stream = stream.unwrap();

        pool.execute(|| {
            handle_connection(stream);
        });
    }

    println!("Shutting down.");
}

fn handle_connection(mut stream: TcpStream) {
    let mut buffer = [0; 512];

    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\r\n\r\n", "hello.html")
    } else if buffer.starts_with(sleep) {
        thread::sleep(Duration::from_secs(5));
        ("HTTP/1.1 200 OK\r\n\r\n", "hello.html")
    } else {
        ("HTTP/1.1 404 NOT FOUND\r\n\r\n", "404.html")
    };

    let contents = fs::read_to_string(filename).unwrap();

    let response = format!("{}{}", status_line, contents);

    stream.write(response.as_bytes()).unwrap();
    stream.flush().unwrap();
}

运行

hello on  master [?] is 📦 0.1.0 via 🦀 1.67.1 
➜ cargo run  
   Compiling hello v0.1.0 (/Users/qiaopengjun/rust/hello)
    Finished dev [unoptimized + debuginfo] target(s) in 0.43s
     Running `target/debug/hello`
Worker 0 got a job; executing.
Shutting down.
Sending terminate message to all workers.
Shutting down all workers.
Shutting down worker 0
Worker 1 got a job; executing.
Worker 2 got a job; executing.
Worker 3 got a job; executing.
Worker 1 got a job; executing.
Worker 0 got a job; executing.
Shutting down worker 1
Shutting down worker 2
Shutting down worker 3

hello on  master [?] is 📦 0.1.0 via 🦀 1.67.1 took 21.9s 
➜