// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
//! A thread pool used to execute functions in parallel.
//!
//! Spawns a specified number of worker threads and replenishes the pool if any worker threads
//! panic.
//!
//! # Examples
//!
//! ## Synchronized with a channel
//!
//! Every thread sends one message over the channel, which then is collected with the `take()`.
//!
//! ```
//! use threadpool::ThreadPool;
//! use std::sync::mpsc::channel;
//!
//! let n_workers = 4;
//! let n_jobs = 8;
//! let pool = ThreadPool::new(n_workers);
//!
//! let (tx, rx) = channel();
//! for _ in 0..n_jobs {
//! let tx = tx.clone();
//! pool.execute(move|| {
//! tx.send(1).expect("channel will be there waiting for the pool");
//! });
//! }
//!
//! assert_eq!(rx.iter().take(n_jobs).fold(0, |a, b| a + b), 8);
//! ```
//!
//! ## Synchronized with a barrier
//!
//! Keep in mind, if a barrier synchronizes more jobs than you have workers in the pool,
//! you will end up with a [deadlock](https://en.wikipedia.org/wiki/Deadlock)
//! at the barrier which is [not considered unsafe]
//! (http://doc.rust-lang.org/reference.html#behavior-not-considered-unsafe).
//!
//! ```
//! use threadpool::ThreadPool;
//! use std::sync::{Arc, Barrier};
//! use std::sync::atomic::{AtomicUsize, Ordering};
//!
//! // create at least as many workers as jobs or you will deadlock yourself
//! let n_workers = 42;
//! let n_jobs = 23;
//! let pool = ThreadPool::new(n_workers);
//! let an_atomic = Arc::new(AtomicUsize::new(0));
//!
//! assert!(n_jobs <= n_workers, "too many jobs, will deadlock");
//!
//! // create a barrier that waits for all jobs plus the starter thread
//! let barrier = Arc::new(Barrier::new(n_jobs + 1));
//! for _ in 0..n_jobs {
//! let barrier = barrier.clone();
//! let an_atomic = an_atomic.clone();
//!
//! pool.execute(move|| {
//! // do the heavy work
//! an_atomic.fetch_add(1, Ordering::Relaxed);
//!
//! // then wait for the other threads
//! barrier.wait();
//! });
//! }
//!
//! // wait for the threads to finish the work
//! barrier.wait();
//! assert_eq!(an_atomic.load(Ordering::SeqCst), 23);
//! ```
extern crate num_cpus;
use std::fmt;
use std::sync::mpsc::{channel, Sender, Receiver};
use std::sync::{Arc, Mutex, Condvar};
use std::sync::atomic::{AtomicUsize, Ordering};
use std::thread;
trait FnBox {
fn call_box(self: Box<Self>);
}
impl<F: FnOnce()> FnBox for F {
fn call_box(self: Box<F>) {
(*self)()
}
}
type Thunk<'a> = Box<FnBox + Send + 'a>;
struct Sentinel<'a> {
shared_data: &'a Arc<ThreadPoolSharedData>,
active: bool,
}
impl<'a> Sentinel<'a> {
fn new(shared_data: &'a Arc<ThreadPoolSharedData>) -> Sentinel<'a> {
Sentinel {
shared_data: shared_data,
active: true,
}
}
/// Cancel and destroy this sentinel.
fn cancel(mut self) {
self.active = false;
}
}
impl<'a> Drop for Sentinel<'a> {
fn drop(&mut self) {
if self.active {
self.shared_data.active_count.fetch_sub(1, Ordering::SeqCst);
if thread::panicking() {
self.shared_data.panic_count.fetch_add(1, Ordering::SeqCst);
}
self.shared_data.no_work_notify_all();
spawn_in_pool(self.shared_data.clone())
}
}
}
/// [`ThreadPool`] factory, which can be used in order to configure the properties of the
/// [`ThreadPool`].
///
/// The three configuration options available:
///
/// * `num_threads`: maximum number of threads that will be alive at any given moment by the built
/// [`ThreadPool`]
/// * `thread_name`: thread name for each of the threads spawned by the built [`ThreadPool`]
/// * `thread_stack_size`: stack size (in bytes) for each of the threads spawned by the built
/// [`ThreadPool`]
///
/// [`ThreadPool`]: struct.ThreadPool.html
///
/// # Examples
///
/// Build a [`ThreadPool`] that uses a maximum of eight threads simultaneously and each thread has
/// a 8 MB stack size:
///
/// ```
/// let pool = threadpool::Builder::new()
/// .num_threads(8)
/// .thread_stack_size(8_000_000)
/// .build();
/// ```
#[derive(Clone, Default)]
pub struct Builder {
num_threads: Option<usize>,
thread_name: Option<String>,
thread_stack_size: Option<usize>,
}
impl Builder {
/// Initiate a new [`Builder`].
///
/// [`Builder`]: struct.Builder.html
///
/// # Examples
///
/// ```
/// let builder = threadpool::Builder::new();
/// ```
pub fn new() -> Builder {
Builder {
num_threads: None,
thread_name: None,
thread_stack_size: None,
}
}
/// Set the maximum number of worker-threads that will be alive at any given moment by the built
/// [`ThreadPool`]. If not specified, defaults the number of threads to the number of CPUs.
///
/// [`ThreadPool`]: struct.ThreadPool.html
///
/// # Panics
///
/// This method will panic if `num_threads` is 0.
///
/// # Examples
///
/// No more than eight threads will be alive simultaneously for this pool:
///
/// ```
/// use std::thread;
///
/// let pool = threadpool::Builder::new()
/// .num_threads(8)
/// .build();
///
/// for _ in 0..100 {
/// pool.execute(|| {
/// println!("Hello from a worker thread!")
/// })
/// }
/// ```
pub fn num_threads(mut self, num_threads: usize) -> Builder {
assert!(num_threads > 0);
self.num_threads = Some(num_threads);
self
}
/// Set the thread name for each of the threads spawned by the built [`ThreadPool`]. If not
/// specified, threads spawned by the thread pool will be unnamed.
///
/// [`ThreadPool`]: struct.ThreadPool.html
///
/// # Examples
///
/// Each thread spawned by this pool will have the name "foo":
///
/// ```
/// use std::thread;
///
/// let pool = threadpool::Builder::new()
/// .thread_name("foo".into())
/// .build();
///
/// for _ in 0..100 {
/// pool.execute(|| {
/// assert_eq!(thread::current().name(), Some("foo"));
/// })
/// }
/// ```
pub fn thread_name(mut self, name: String) -> Builder {
self.thread_name = Some(name);
self
}
/// Set the stack size (in bytes) for each of the threads spawned by the built [`ThreadPool`].
/// If not specified, threads spawned by the threadpool will have a stack size [as specified in
/// the `std::thread` documentation][thread].
///
/// [thread]: https://doc.rust-lang.org/nightly/std/thread/index.html#stack-size
/// [`ThreadPool`]: struct.ThreadPool.html
///
/// # Examples
///
/// Each thread spawned by this pool will have a 4 MB stack:
///
/// ```
/// let pool = threadpool::Builder::new()
/// .thread_stack_size(4_000_000)
/// .build();
///
/// for _ in 0..100 {
/// pool.execute(|| {
/// println!("This thread has a 4 MB stack size!");
/// })
/// }
/// ```
pub fn thread_stack_size(mut self, size: usize) -> Builder {
self.thread_stack_size = Some(size);
self
}
/// Finalize the [`Builder`] and build the [`ThreadPool`].
///
/// [`Builder`]: struct.Builder.html
/// [`ThreadPool`]: struct.ThreadPool.html
///
/// # Examples
///
/// ```
/// let pool = threadpool::Builder::new()
/// .num_threads(8)
/// .thread_stack_size(4_000_000)
/// .build();
/// ```
pub fn build(self) -> ThreadPool {
let (tx, rx) = channel::<Thunk<'static>>();
let num_threads = self.num_threads.unwrap_or_else(num_cpus::get);
let shared_data = Arc::new(ThreadPoolSharedData {
name: self.thread_name,
job_receiver: Mutex::new(rx),
empty_condvar: Condvar::new(),
empty_trigger: Mutex::new(()),
join_generation: AtomicUsize::new(0),
queued_count: AtomicUsize::new(0),
active_count: AtomicUsize::new(0),
max_thread_count: AtomicUsize::new(num_threads),
panic_count: AtomicUsize::new(0),
stack_size: self.thread_stack_size,
});
// Threadpool threads
for _ in 0..num_threads {
spawn_in_pool(shared_data.clone());
}
ThreadPool {
jobs: tx,
shared_data: shared_data,
}
}
}
struct ThreadPoolSharedData {
name: Option<String>,
job_receiver: Mutex<Receiver<Thunk<'static>>>,
empty_trigger: Mutex<()>,
empty_condvar: Condvar,
join_generation: AtomicUsize,
queued_count: AtomicUsize,
active_count: AtomicUsize,
max_thread_count: AtomicUsize,
panic_count: AtomicUsize,
stack_size: Option<usize>,
}
impl ThreadPoolSharedData {
fn has_work(&self) -> bool {
self.queued_count.load(Ordering::SeqCst) > 0 || self.active_count.load(Ordering::SeqCst) > 0
}
/// Notify all observers joining this pool if there is no more work to do.
fn no_work_notify_all(&self) {
if !self.has_work() {
*self.empty_trigger.lock().expect(
"Unable to notify all joining threads",
);
self.empty_condvar.notify_all();
}
}
}
/// Abstraction of a thread pool for basic parallelism.
pub struct ThreadPool {
// How the threadpool communicates with subthreads.
//
// This is the only such Sender, so when it is dropped all subthreads will
// quit.
jobs: Sender<Thunk<'static>>,
shared_data: Arc<ThreadPoolSharedData>,
}
impl ThreadPool {
/// Creates a new thread pool capable of executing `num_threads` number of jobs concurrently.
///
/// # Panics
///
/// This function will panic if `num_threads` is 0.
///
/// # Examples
///
/// Create a new thread pool capable of executing four jobs concurrently:
///
/// ```
/// use threadpool::ThreadPool;
///
/// let pool = ThreadPool::new(4);
/// ```
pub fn new(num_threads: usize) -> ThreadPool {
Builder::new().num_threads(num_threads).build()
}
/// Creates a new thread pool capable of executing `num_threads` number of jobs concurrently.
/// Each thread will have the [name][thread name] `name`.
///
/// # Panics
///
/// This function will panic if `num_threads` is 0.
///
/// # Examples
///
/// ```rust
/// use std::thread;
/// use threadpool::ThreadPool;
///
/// let pool = ThreadPool::with_name("worker".into(), 2);
/// for _ in 0..2 {
/// pool.execute(|| {
/// assert_eq!(
/// thread::current().name(),
/// Some("worker")
/// );
/// });
/// }
/// pool.join();
/// ```
///
/// [thread name]: https://doc.rust-lang.org/std/thread/struct.Thread.html#method.name
pub fn with_name(name: String, num_threads: usize) -> ThreadPool {
Builder::new()
.num_threads(num_threads)
.thread_name(name)
.build()
}
/// **Deprecated: Use [`ThreadPool::with_name`](#method.with_name)**
#[inline(always)]
#[deprecated(since = "1.4.0", note = "use ThreadPool::with_name")]
pub fn new_with_name(name: String, num_threads: usize) -> ThreadPool {
Self::with_name(name, num_threads)
}
/// Executes the function `job` on a thread in the pool.
///
/// # Examples
///
/// Execute four jobs on a thread pool that can run two jobs concurrently:
///
/// ```
/// use threadpool::ThreadPool;
///
/// let pool = ThreadPool::new(2);
/// pool.execute(|| println!("hello"));
/// pool.execute(|| println!("world"));
/// pool.execute(|| println!("foo"));
/// pool.execute(|| println!("bar"));
/// pool.join();
/// ```
pub fn execute<F>(&self, job: F)
where
F: FnOnce() + Send + 'static,
{
self.shared_data.queued_count.fetch_add(1, Ordering::SeqCst);
self.jobs.send(Box::new(job)).expect(
"ThreadPool::execute unable to send job into queue.",
);
}
/// 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 = ThreadPool::new(2);
/// 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 queued_count(&self) -> usize {
self.shared_data.queued_count.load(Ordering::Relaxed)
}
/// Returns the number of currently active threads.
///
/// # Examples
///
/// ```
/// use threadpool::ThreadPool;
/// use std::time::Duration;
/// use std::thread::sleep;
///
/// let pool = ThreadPool::new(4);
/// 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 active_count(&self) -> usize {
self.shared_data.active_count.load(Ordering::SeqCst)
}
/// Returns the maximum number of threads the pool will execute concurrently.
///
/// # Examples
///
/// ```
/// use threadpool::ThreadPool;
///
/// let mut pool = ThreadPool::new(4);
/// assert_eq!(4, pool.max_count());
///
/// pool.set_num_threads(8);
/// assert_eq!(8, pool.max_count());
/// ```
pub fn max_count(&self) -> usize {
self.shared_data.max_thread_count.load(Ordering::Relaxed)
}
/// Returns the number of panicked threads over the lifetime of the pool.
///
/// # Examples
///
/// ```
/// use threadpool::ThreadPool;
///
/// let pool = ThreadPool::new(4);
/// 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 panic_count(&self) -> usize {
self.shared_data.panic_count.load(Ordering::Relaxed)
}
/// **Deprecated: Use [`ThreadPool::set_num_threads`](#method.set_num_threads)**
#[deprecated(since = "1.3.0", note = "use ThreadPool::set_num_threads")]
pub fn set_threads(&mut self, num_threads: usize) {
self.set_num_threads(num_threads)
}
/// Sets the number of worker-threads to use as `num_threads`.
/// 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_threads` is 0.
///
/// # Examples
///
/// ```
/// use threadpool::ThreadPool;
/// use std::time::Duration;
/// use std::thread::sleep;
///
/// let mut pool = ThreadPool::new(4);
/// 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_threads(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_threads(4);
///
/// assert_eq!(8, pool.active_count());
/// assert_eq!(2, pool.queued_count());
/// ```
pub fn set_num_threads(&mut self, num_threads: usize) {
assert!(num_threads >= 1);
let prev_num_threads = self.shared_data.max_thread_count.swap(
num_threads,
Ordering::Release,
);
if let Some(num_spawn) = num_threads.checked_sub(prev_num_threads) {
// Spawn new threads
for _ in 0..num_spawn {
spawn_in_pool(self.shared_data.clone());
}
}
}
/// 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.
///
/// # Examples
///
/// ```
/// use threadpool::ThreadPool;
/// use std::sync::Arc;
/// use std::sync::atomic::{AtomicUsize, Ordering};
///
/// let pool = ThreadPool::new(8);
/// 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));
/// ```
pub fn join(&self) {
// fast path requires no mutex
if self.shared_data.has_work() == false {
return ();
}
let generation = self.shared_data.join_generation.load(Ordering::SeqCst);
let mut lock = self.shared_data.empty_trigger.lock().unwrap();
while generation == self.shared_data.join_generation.load(Ordering::Relaxed) &&
self.shared_data.has_work() {
lock = self.shared_data.empty_condvar.wait(lock).unwrap();
}
// increase generation if we are the first thread to come out of the loop
self.shared_data.join_generation.compare_and_swap(generation, generation.wrapping_add(1), Ordering::SeqCst);
}
}
impl Clone for ThreadPool {
/// Cloning a pool will create a new handle to the pool.
/// The behavior is similar to [Arc](https://doc.rust-lang.org/stable/std/sync/struct.Arc.html).
///
/// We could for example submit jobs from multiple threads concurrently.
///
/// ```
/// use threadpool::ThreadPool;
/// use std::thread;
/// use std::sync::mpsc::channel;
///
/// let pool = ThreadPool::with_name("clone example".into(), 2);
///
/// let results = (0..2)
/// .map(|i| {
/// let pool = pool.clone();
/// thread::spawn(move || {
/// let (tx, rx) = channel();
/// 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(&self) -> ThreadPool {
ThreadPool {
jobs: self.jobs.clone(),
shared_data: self.shared_data.clone(),
}
}
}
/// Create a thread pool with one thread per CPU.
/// On machines with hyperthreading,
/// this will create one thread per hyperthread.
impl Default for ThreadPool {
fn default() -> Self {
ThreadPool::new(num_cpus::get())
}
}
impl fmt::Debug for ThreadPool {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
f.debug_struct("ThreadPool")
.field("name", &self.shared_data.name)
.field("queued_count", &self.queued_count())
.field("active_count", &self.active_count())
.field("max_count", &self.max_count())
.finish()
}
}
impl PartialEq for ThreadPool {
/// Check if you are working with the same pool
///
/// ```
/// use threadpool::ThreadPool;
///
/// let a = ThreadPool::new(2);
/// let b = ThreadPool::new(2);
///
/// assert_eq!(a, a);
/// assert_eq!(b, b);
///
/// # // TODO: change this to assert_ne in the future
/// assert!(a != b);
/// assert!(b != a);
/// ```
fn eq(&self, other: &ThreadPool) -> bool {
let a: &ThreadPoolSharedData = &*self.shared_data;
let b: &ThreadPoolSharedData = &*other.shared_data;
a as *const ThreadPoolSharedData == b as *const ThreadPoolSharedData
// with rust 1.17 and late:
// Arc::ptr_eq(&self.shared_data, &other.shared_data)
}
}
impl Eq for ThreadPool {}
fn spawn_in_pool(shared_data: Arc<ThreadPoolSharedData>) {
let mut builder = thread::Builder::new();
if let Some(ref name) = shared_data.name {
builder = builder.name(name.clone());
}
if let Some(ref stack_size) = shared_data.stack_size {
builder = builder.stack_size(stack_size.to_owned());
}
builder
.spawn(move || {
// Will spawn a new thread on panic unless it is cancelled.
let sentinel = Sentinel::new(&shared_data);
loop {
// Shutdown this thread if the pool has become smaller
let thread_counter_val = shared_data.active_count.load(Ordering::Acquire);
let max_thread_count_val = shared_data.max_thread_count.load(Ordering::Relaxed);
if thread_counter_val >= max_thread_count_val {
break;
}
let message = {
// Only lock jobs for the time it takes
// to get a job, not run it.
let lock = shared_data.job_receiver.lock().expect(
"Worker thread unable to lock job_receiver",
);
lock.recv()
};
let job = match message {
Ok(job) => job,
// The ThreadPool was dropped.
Err(..) => break,
};
// Do not allow IR around the job execution
shared_data.active_count.fetch_add(1, Ordering::SeqCst);
shared_data.queued_count.fetch_sub(1, Ordering::SeqCst);
job.call_box();
shared_data.active_count.fetch_sub(1, Ordering::SeqCst);
shared_data.no_work_notify_all();
}
sentinel.cancel();
})
.unwrap();
}
#[cfg(test)]
mod test {
use super::{ThreadPool, Builder};
use std::sync::{Arc, Barrier};
use std::sync::atomic::{AtomicUsize, Ordering};
use std::sync::mpsc::{sync_channel, channel};
use std::thread::{self, sleep};
use std::time::Duration;
const TEST_TASKS: usize = 4;
#[test]
fn test_set_num_threads_increasing() {
let new_thread_amount = TEST_TASKS + 8;
let mut pool = ThreadPool::new(TEST_TASKS);
for _ in 0..TEST_TASKS {
pool.execute(move || sleep(Duration::from_secs(23)));
}
sleep(Duration::from_secs(1));
assert_eq!(pool.active_count(), TEST_TASKS);
pool.set_num_threads(new_thread_amount);
for _ in 0..(new_thread_amount - TEST_TASKS) {
pool.execute(move || sleep(Duration::from_secs(23)));
}
sleep(Duration::from_secs(1));
assert_eq!(pool.active_count(), new_thread_amount);
pool.join();
}
#[test]
fn test_set_num_threads_decreasing() {
let new_thread_amount = 2;
let mut pool = ThreadPool::new(TEST_TASKS);
for _ in 0..TEST_TASKS {
pool.execute(move || { 1 + 1; });
}
pool.set_num_threads(new_thread_amount);
for _ in 0..new_thread_amount {
pool.execute(move || sleep(Duration::from_secs(23)));
}
sleep(Duration::from_secs(1));
assert_eq!(pool.active_count(), new_thread_amount);
pool.join();
}
#[test]
fn test_active_count() {
let pool = ThreadPool::new(TEST_TASKS);
for _ in 0..2 * TEST_TASKS {
pool.execute(move || loop {
sleep(Duration::from_secs(10))
});
}
sleep(Duration::from_secs(1));
let active_count = pool.active_count();
assert_eq!(active_count, TEST_TASKS);
let initialized_count = pool.max_count();
assert_eq!(initialized_count, TEST_TASKS);
}
#[test]
fn test_works() {
let pool = ThreadPool::new(TEST_TASKS);
let (tx, rx) = channel();
for _ in 0..TEST_TASKS {
let tx = tx.clone();
pool.execute(move || { tx.send(1).unwrap(); });
}
assert_eq!(rx.iter().take(TEST_TASKS).fold(0, |a, b| a + b), TEST_TASKS);
}
#[test]
#[should_panic]
fn test_zero_tasks_panic() {
ThreadPool::new(0);
}
#[test]
fn test_recovery_from_subtask_panic() {
let pool = ThreadPool::new(TEST_TASKS);
// Panic all the existing threads.
for _ in 0..TEST_TASKS {
pool.execute(move || panic!("Ignore this panic, it must!"));
}
pool.join();
assert_eq!(pool.panic_count(), TEST_TASKS);
// Ensure new threads were spawned to compensate.
let (tx, rx) = channel();
for _ in 0..TEST_TASKS {
let tx = tx.clone();
pool.execute(move || { tx.send(1).unwrap(); });
}
assert_eq!(rx.iter().take(TEST_TASKS).fold(0, |a, b| a + b), TEST_TASKS);
}
#[test]
fn test_should_not_panic_on_drop_if_subtasks_panic_after_drop() {
let pool = ThreadPool::new(TEST_TASKS);
let waiter = Arc::new(Barrier::new(TEST_TASKS + 1));
// Panic all the existing threads in a bit.
for _ in 0..TEST_TASKS {
let waiter = waiter.clone();
pool.execute(move || {
waiter.wait();
panic!("Ignore this panic, it should!");
});
}
drop(pool);
// Kick off the failure.
waiter.wait();
}
#[test]
fn test_massive_task_creation() {
let test_tasks = 4_200_000;
let pool = ThreadPool::new(TEST_TASKS);
let b0 = Arc::new(Barrier::new(TEST_TASKS + 1));
let b1 = Arc::new(Barrier::new(TEST_TASKS + 1));
let (tx, rx) = channel();
for i in 0..test_tasks {
let tx = tx.clone();
let (b0, b1) = (b0.clone(), b1.clone());
pool.execute(move || {
// Wait until the pool has been filled once.
if i < TEST_TASKS {
b0.wait();
// wait so the pool can be measured
b1.wait();
}
tx.send(1).is_ok();
});
}
b0.wait();
assert_eq!(pool.active_count(), TEST_TASKS);
b1.wait();
assert_eq!(rx.iter().take(test_tasks).fold(0, |a, b| a + b), test_tasks);
pool.join();
let atomic_active_count = pool.active_count();
assert!(
atomic_active_count == 0,
"atomic_active_count: {}",
atomic_active_count
);
}
#[test]
fn test_shrink() {
let test_tasks_begin = TEST_TASKS + 2;
let mut pool = ThreadPool::new(test_tasks_begin);
let b0 = Arc::new(Barrier::new(test_tasks_begin + 1));
let b1 = Arc::new(Barrier::new(test_tasks_begin + 1));
for _ in 0..test_tasks_begin {
let (b0, b1) = (b0.clone(), b1.clone());
pool.execute(move || {
b0.wait();
b1.wait();
});
}
let b2 = Arc::new(Barrier::new(TEST_TASKS + 1));
let b3 = Arc::new(Barrier::new(TEST_TASKS + 1));
for _ in 0..TEST_TASKS {
let (b2, b3) = (b2.clone(), b3.clone());
pool.execute(move || {
b2.wait();
b3.wait();
});
}
b0.wait();
pool.set_num_threads(TEST_TASKS);
assert_eq!(pool.active_count(), test_tasks_begin);
b1.wait();
b2.wait();
assert_eq!(pool.active_count(), TEST_TASKS);
b3.wait();
}
#[test]
fn test_name() {
let name = "test";
let mut pool = ThreadPool::with_name(name.to_owned(), 2);
let (tx, rx) = sync_channel(0);
// initial thread should share the name "test"
for _ in 0..2 {
let tx = tx.clone();
pool.execute(move || {
let name = thread::current().name().unwrap().to_owned();
tx.send(name).unwrap();
});
}
// new spawn thread should share the name "test" too.
pool.set_num_threads(3);
let tx_clone = tx.clone();
pool.execute(move || {
let name = thread::current().name().unwrap().to_owned();
tx_clone.send(name).unwrap();
panic!();
});
// recover thread should share the name "test" too.
pool.execute(move || {
let name = thread::current().name().unwrap().to_owned();
tx.send(name).unwrap();
});
for thread_name in rx.iter().take(4) {
assert_eq!(name, thread_name);
}
}
#[test]
fn test_debug() {
let pool = ThreadPool::new(4);
let debug = format!("{:?}", pool);
assert_eq!(
debug,
"ThreadPool { name: None, queued_count: 0, active_count: 0, max_count: 4 }"
);
let pool = ThreadPool::with_name("hello".into(), 4);
let debug = format!("{:?}", pool);
assert_eq!(
debug,
"ThreadPool { name: Some(\"hello\"), queued_count: 0, active_count: 0, max_count: 4 }"
);
let pool = ThreadPool::new(4);
pool.execute(move || sleep(Duration::from_secs(5)));
sleep(Duration::from_secs(1));
let debug = format!("{:?}", pool);
assert_eq!(
debug,
"ThreadPool { name: None, queued_count: 0, active_count: 1, max_count: 4 }"
);
}
#[test]
fn test_repeate_join() {
let pool = ThreadPool::with_name("repeate join test".into(), 8);
let test_count = Arc::new(AtomicUsize::new(0));
for _ in 0..42 {
let test_count = test_count.clone();
pool.execute(move || {
sleep(Duration::from_secs(2));
test_count.fetch_add(1, Ordering::Release);
});
}
println!("{:?}", pool);
pool.join();
assert_eq!(42, test_count.load(Ordering::Acquire));
for _ in 0..42 {
let test_count = test_count.clone();
pool.execute(move || {
sleep(Duration::from_secs(2));
test_count.fetch_add(1, Ordering::Relaxed);
});
}
pool.join();
assert_eq!(84, test_count.load(Ordering::Relaxed));
}
#[test]
fn test_multi_join() {
use std::sync::mpsc::TryRecvError::*;
// Toggle the following lines to debug the deadlock
fn error(_s: String) {
//use ::std::io::Write;
//let stderr = ::std::io::stderr();
//let mut stderr = stderr.lock();
//stderr.write(&_s.as_bytes()).is_ok();
}
let pool0 = ThreadPool::with_name("multi join pool0".into(), 4);
let pool1 = ThreadPool::with_name("multi join pool1".into(), 4);
let (tx, rx) = channel();
for i in 0..8 {
let pool1 = pool1.clone();
let pool0_ = pool0.clone();
let tx = tx.clone();
pool0.execute(move || {
pool1.execute(move || {
error(format!("p1: {} -=- {:?}\n", i, pool0_));
pool0_.join();
error(format!("p1: send({})\n", i));
tx.send(i).expect("send i from pool1 -> main");
});
error(format!("p0: {}\n", i));
});
}
drop(tx);
assert_eq!(rx.try_recv(), Err(Empty));
error(format!("{:?}\n{:?}\n", pool0, pool1));
pool0.join();
error(format!("pool0.join() complete =-= {:?}", pool1));
pool1.join();
error("pool1.join() complete\n".into());
assert_eq!(
rx.iter().fold(0, |acc, i| acc + i),
0 + 1 + 2 + 3 + 4 + 5 + 6 + 7
);
}
#[test]
fn test_empty_pool() {
// Joining an empty pool must return imminently
let pool = ThreadPool::new(4);
pool.join();
assert!(true);
}
#[test]
fn test_no_fun_or_joy() {
// What happens when you keep adding jobs after a join
fn sleepy_function() {
sleep(Duration::from_secs(6));
}
let pool = ThreadPool::with_name("no fun or joy".into(), 8);
pool.execute(sleepy_function);
let p_t = pool.clone();
thread::spawn(move || {
(0..23).map(|_| p_t.execute(sleepy_function)).count();
});
pool.join();
}
#[test]
fn test_clone() {
let pool = ThreadPool::with_name("clone example".into(), 2);
// This batch of jobs will occupy the pool for some time
for _ in 0..6 {
pool.execute(move || { sleep(Duration::from_secs(2)); });
}
// The following jobs will be inserted into the pool in a random fashion
let t0 = {
let pool = pool.clone();
thread::spawn(move || {
// wait for the first batch of tasks to finish
pool.join();
let (tx, rx) = channel();
for i in 0..42 {
let tx = tx.clone();
pool.execute(move || { tx.send(i).expect("channel will be waiting"); });
}
drop(tx);
rx.iter().fold(
0,
|accumulator, element| accumulator + element,
)
})
};
let t1 = {
let pool = pool.clone();
thread::spawn(move || {
// wait for the first batch of tasks to finish
pool.join();
let (tx, rx) = channel();
for i in 1..12 {
let tx = tx.clone();
pool.execute(move || { tx.send(i).expect("channel will be waiting"); });
}
drop(tx);
rx.iter().fold(
1,
|accumulator, element| accumulator * element,
)
})
};
assert_eq!(
861,
t0.join().expect(
"thread 0 will return after calculating additions",
)
);
assert_eq!(
39916800,
t1.join().expect(
"thread 1 will return after calculating multiplications",
)
);
}
#[test]
fn test_sync_shared_data() {
fn assert_sync<T: Sync>() {}
assert_sync::<super::ThreadPoolSharedData>();
}
#[test]
fn test_send_shared_data() {
fn assert_send<T: Send>() {}
assert_send::<super::ThreadPoolSharedData>();
}
#[test]
fn test_send() {
fn assert_send<T: Send>() {}
assert_send::<ThreadPool>();
}
#[test]
fn test_cloned_eq() {
let a = ThreadPool::new(2);
assert_eq!(a, a.clone());
}
#[test]
/// The scenario is joining threads should not be stuck once their wave
/// of joins has completed. So once one thread joining on a pool has
/// succeded other threads joining on the same pool must get out even if
/// the thread is used for other jobs while the first group is finishing
/// their join
///
/// In this example this means the waiting threads will exit the join in
/// groups of four because the waiter pool has four workers.
fn test_join_wavesurfer() {
let n_cycles = 4;
let n_workers = 4;
let (tx, rx) = channel();
let builder = Builder::new().num_threads(n_workers)
.thread_name("join wavesurfer".into());
let p_waiter = builder.clone().build();
let p_clock = builder.build();
let barrier = Arc::new(Barrier::new(3));
let wave_clock = Arc::new(AtomicUsize::new(0));
let clock_thread = {
let barrier = barrier.clone();
let wave_clock = wave_clock.clone();
thread::spawn(move || {
barrier.wait();
for wave_num in 0..n_cycles {
wave_clock.store(wave_num, Ordering::SeqCst);
sleep(Duration::from_secs(1));
}
})
};
{
let barrier = barrier.clone();
p_clock.execute(move || {
barrier.wait();
// this sleep is for stabilisation on weaker platforms
sleep(Duration::from_millis(100));
});
}
// prepare three waves of jobs
for i in 0..3*n_workers {
let p_clock = p_clock.clone();
let tx = tx.clone();
let wave_clock = wave_clock.clone();
p_waiter.execute(move || {
let now = wave_clock.load(Ordering::SeqCst);
p_clock.join();
// submit jobs for the second wave
p_clock.execute(|| sleep(Duration::from_secs(1)));
let clock = wave_clock.load(Ordering::SeqCst);
tx.send((now, clock, i)).unwrap();
});
}
println!("all scheduled at {}", wave_clock.load(Ordering::SeqCst));
barrier.wait();
p_clock.join();
//p_waiter.join();
drop(tx);
let mut hist = vec![0; n_cycles];
let mut data = vec![];
for (now, after, i) in rx.iter() {
let mut dur = after - now;
if dur >= n_cycles -1 {
dur = n_cycles -1;
}
hist[dur] += 1;
data.push((now, after, i));
}
for (i, n) in hist.iter().enumerate() {
println!("\t{}: {} {}", i, n, &*(0..*n).fold("".to_owned(), |s, _| s + "*"));
}
assert!(data.iter()
.all(|&(cycle, stop, i)| {
if i < n_workers {
cycle == stop
} else {
cycle < stop
}
}));
clock_thread.join().unwrap();
}
}