AkurAI-Framework / crates/http/src/pool.rs

Latest change 3ad787ae157fc60f711c536c1811b3b199b0ac1a - init: AkurAI-Framework foundation (history reset after FS corruption) by Ólafur Búi Ólafsson

//! A minimal fixed-size thread pool built from `std::sync::mpsc` + `Mutex`.
//!
//! One bounded set of worker threads pull jobs off a shared channel. This is
//! the classic Rust-book design, kept deliberately small: the server hands it
//! one closure per accepted connection.

use std::sync::{mpsc, Arc, Mutex};
use std::thread;

type Job = Box<dyn FnOnce() + Send + 'static>;

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

impl ThreadPool {
    /// Create a pool with `size` worker threads. Panics if `size == 0`.
    pub fn new(size: usize) -> ThreadPool {
        assert!(size > 0, "thread pool size must be > 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),
        }
    }

    /// Queue a job for execution on the next free worker.
    pub fn execute<F>(&self, f: F)
    where
        F: FnOnce() + Send + 'static,
    {
        if let Some(sender) = &self.sender {
            // If all workers have gone, the send fails; we drop the job rather
            // than panic, since that only happens during shutdown.
            let _ = sender.send(Box::new(f));
        }
    }
}

impl Drop for ThreadPool {
    fn drop(&mut self) {
        // Closing the channel lets every worker's `recv` return `Err`, ending
        // its loop, so the joins below complete.
        drop(self.sender.take());
        for worker in &mut self.workers {
            if let Some(thread) = worker.thread.take() {
                let _ = thread.join();
            }
        }
    }
}

struct Worker {
    #[allow(dead_code)]
    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) => job(),
                Err(_) => break, // channel closed → shut down
            }
        });
        Worker {
            id,
            thread: Some(thread),
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use std::sync::atomic::{AtomicUsize, Ordering};

    #[test]
    fn runs_all_queued_jobs() {
        let counter = Arc::new(AtomicUsize::new(0));
        {
            let pool = ThreadPool::new(4);
            for _ in 0..100 {
                let c = Arc::clone(&counter);
                pool.execute(move || {
                    c.fetch_add(1, Ordering::SeqCst);
                });
            }
            // pool drops here → joins all workers → all jobs have run
        }
        assert_eq!(counter.load(Ordering::SeqCst), 100);
    }
}