Struct ThreadPool

pub struct ThreadPool { /* private fields */ }

Abstraction of a thread pool for basic parallelism.

Implementations

impl ThreadPool

pub fn execute<F>(&self, job: F)

where F: FnOnce() + Send + 'static,

Executes the function job on a thread in the pool.

Examples

Execute four jobs on a thread pool that can run two jobs concurrently:

let pool = lft_rust::lft_auto_config();
pool.execute(|| println!("hello"));
pool.execute(|| println!("world"));
pool.execute(|| println!("foo"));
pool.execute(|| println!("bar"));
pool.join();

pub fn queued_count(&self) -> usize

Returns the number of jobs waiting to executed in the pool.

Examples

use threadpool::ThreadPool;
use std::time::Duration;
use std::thread::sleep;

let pool = lft_rust::lft_builder()
                    .num_workers(2)
                    .build();
for _ in 0..10 {
    pool.execute(|| {
        sleep(Duration::from_secs(100));
    });
}

sleep(Duration::from_secs(1)); // wait for threads to start
assert_eq!(8, pool.queued_count());

pub fn active_count(&self) -> usize

Returns the number of currently active worker threads.

Examples

use std::time::Duration;
use std::thread::sleep;

let pool = lft_rust::lft_builder()
                    .num_workers(4)
                    .build();
for _ in 0..10 {
    pool.execute(move || {
        sleep(Duration::from_secs(100));
    });
}

sleep(Duration::from_secs(1)); // wait for threads to start
assert_eq!(4, pool.active_count());

pub fn max_count(&self) -> usize

Returns the maximum number of threads the pool will execute concurrently.

Examples

let pool = lft_rust::lft_builder()
                    .num_workers(4)
                    .build();
assert_eq!(4, pool.max_count());

pool.set_num_workers(8);
assert_eq!(8, pool.max_count());

pub fn num_workers(&self) -> usize

Returns the number of workers running in the threadpool.

pub fn panic_count(&self) -> usize

Returns the number of panicked threads over the lifetime of the pool.

Examples

let pool = lft_rust::lft_builder()
                    .num_workers(4)
                    .build();
for n in 0..10 {
    pool.execute(move || {
        // simulate a panic
        if n % 2 == 0 {
            panic!()
        }
    });
}
pool.join();

assert_eq!(5, pool.panic_count());

pub fn spawn_extra_one_worker(&self)

Sets the number of worker-threads to use as num_workers. Can be used to change the threadpool size during runtime. Will not abort already running or waiting threads.

Panics

This function will panic if num_workers is 0.

Examples

use std::time::Duration;
use std::thread::sleep;

let  pool = threadpool::builder().num_workers(4).build();
for _ in 0..10 {
    pool.execute(move || {
        sleep(Duration::from_secs(100));
    });
}

sleep(Duration::from_secs(1)); // wait for threads to start
assert_eq!(4, pool.active_count());
assert_eq!(6, pool.queued_count());

// Increase thread capacity of the pool
pool.set_num_workers(8);

sleep(Duration::from_secs(1)); // wait for new threads to start
assert_eq!(8, pool.active_count());
assert_eq!(2, pool.queued_count());

// Decrease thread capacity of the pool
// No active threads are killed
pool.set_num_workers(4);

assert_eq!(8, pool.active_count());
assert_eq!(2, pool.queued_count());

Spawn an extra worker thread. Can be used to increase the number of work threads during runtimes. If the number of threads is already the maximum, it will print out an warning.

Examples

use std::time::Duration;
use std::thread::sleep;

let  pool = threadpool::builder().num_workers(4).build();
for _ in 0..10 {
    pool.execute(move || {
        sleep(Duration::from_secs(100));
    });
pool.spawn_extra_one_worker();

pub fn shutdown_one_worker(&self)

Shutdown a worker thread in the threadpool. Can be used to increase the number of work threads during runtimes. If the number of threads is already 0, it will print out an warning.

Examples

use std::time::Duration;
use std::thread::sleep;

let  pool = threadpool::builder().num_workers(4).build();
for _ in 0..10 {
    pool.execute(move || {
        sleep(Duration::from_secs(100));
    });
pool.spawn_extra_one_worker();

pub fn join(&self)

Block the current thread until all jobs in the pool have been executed.

Calling join on an empty pool will cause an immediate return. join may be called from multiple threads concurrently. A join is an atomic point in time. All threads joining before the join event will exit together even if the pool is processing new jobs by the time they get scheduled.

Calling join from a thread within the pool will cause a deadlock. This behavior is considered safe.

Note: Join will not stop the worker threads. You will need to drop all instances of ThreadPool for the worker threads to terminate.

Examples

use threadpool::ThreadPool;
use std::sync::Arc;
use std::sync::atomic::{AtomicUsize, Ordering};

let pool = lft_rust::lft_auto_config();
let test_count = Arc::new(AtomicUsize::new(0));

for _ in 0..42 {
    let test_count = test_count.clone();
    pool.execute(move || {
        test_count.fetch_add(1, Ordering::Relaxed);
    });
}

pool.join();
assert_eq!(42, test_count.load(Ordering::Relaxed));

Trait Implementations

impl Clone for ThreadPool

fn clone(&self) -> ThreadPool

Cloning a pool will create a new handle to the pool. The behavior is similar to Arc.

We could for example submit jobs from multiple threads concurrently.

use std::thread;
use crossbeam_channel::unbounded;

let pool = lft_rust::lft_builder()
                .worker_name("clone example")
                .num_workers(2)
                .build();

let results = (0..2)
    .map(|i| {
        let pool = pool.clone();
        thread::spawn(move || {
            let (tx, rx) = unbounded();
            for i in 1..12 {
                let tx = tx.clone();
                pool.execute(move || {
                    tx.send(i).expect("channel will be waiting");
                });
            }
            drop(tx);
            if i == 0 {
                rx.iter().fold(0, |accumulator, element| accumulator + element)
            } else {
                rx.iter().fold(1, |accumulator, element| accumulator * element)
            }
        })
    })
    .map(|join_handle| join_handle.join().expect("collect results from threads"))
    .collect::<Vec<usize>>();

assert_eq!(vec![66, 39916800], results);

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for ThreadPool

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl PartialEq for ThreadPool

fn eq(&self, other: &ThreadPool) -> bool

Check if you are working with the same pool

let a = lft_rust::lft_auto_config();
let b = lft_rust::lft_auto_config();

assert_eq!(a, a);
assert_eq!(b, b);

assert_ne!(a, b);
assert_ne!(b, a);

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Eq for ThreadPool