src/doc/book/listings/ch20-web-server/listing-20-25/src/lib.rs

   1 // ANCHOR: here
   2 use std::sync::mpsc;
   3 use std::sync::Arc;
   4 use std::sync::Mutex;
   5 use std::thread;
   6
   7 pub struct ThreadPool {
   8     workers: Vec<Worker>,
   9     sender: mpsc::Sender<Message>,
  10 }
  11
  12 type Job = Box<dyn FnOnce() + Send + 'static>;
  13
  14 enum Message {
  15     NewJob(Job),
  16     Terminate,
  17 }
  18
  19 impl ThreadPool {
  20     /// Create a new ThreadPool.
  21     ///
  22     /// The size is the number of threads in the pool.
  23     ///
  24     /// # Panics
  25     ///
  26     /// The `new` function will panic if the size is zero.
  27     pub fn new(size: usize) -> ThreadPool {
  28         assert!(size > 0);
  29
  30         let (sender, receiver) = mpsc::channel();
  31
  32         let receiver = Arc::new(Mutex::new(receiver));
  33
  34         let mut workers = Vec::with_capacity(size);
  35
  36         for id in 0..size {
  37             workers.push(Worker::new(id, Arc::clone(&receiver)));
  38         }
  39
  40         ThreadPool { workers, sender }
  41     }
  42
  43     pub fn execute<F>(&self, f: F)
  44     where
  45         F: FnOnce() + Send + 'static,
  46     {
  47         let job = Box::new(f);
  48
  49         self.sender.send(Message::NewJob(job)).unwrap();
  50     }
  51 }
  52
  53 impl Drop for ThreadPool {
  54     fn drop(&mut self) {
  55         println!("Sending terminate message to all workers.");
  56
  57         for _ in &self.workers {
  58             self.sender.send(Message::Terminate).unwrap();
  59         }
  60
  61         println!("Shutting down all workers.");
  62
  63         for worker in &mut self.workers {
  64             println!("Shutting down worker {}", worker.id);
  65
  66             if let Some(thread) = worker.thread.take() {
  67                 thread.join().unwrap();
  68             }
  69         }
  70     }
  71 }
  72
  73 struct Worker {
  74     id: usize,
  75     thread: Option<thread::JoinHandle<()>>,
  76 }
  77
  78 impl Worker {
  79     fn new(id: usize, receiver: Arc<Mutex<mpsc::Receiver<Message>>>) -> Worker {
  80         let thread = thread::spawn(move || loop {
  81             let message = receiver.lock().unwrap().recv().unwrap();
  82
  83             match message {
  84                 Message::NewJob(job) => {
  85                     println!("Worker {} got a job; executing.", id);
  86
  87                     job();
  88                 }
  89                 Message::Terminate => {
  90                     println!("Worker {} was told to terminate.", id);
  91
  92                     break;
  93                 }
  94             }
  95         });
  96
  97         Worker {
  98             id,
  99             thread: Some(thread),
 100         }
 101     }
 102 }
 103 // ANCHOR_END: here
 104
 105 fn main() {}