1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345
//! [![crates.io version](https://img.shields.io/crates/v/safina-threadpool.svg)](https://crates.io/crates/safina-threadpool) //! [![license: Apache 2.0](https://gitlab.com/leonhard-llc/safina-rs/-/raw/main/license-apache-2.0.svg)](http://www.apache.org/licenses/LICENSE-2.0) //! [![unsafe forbidden](https://gitlab.com/leonhard-llc/safina-rs/-/raw/main/unsafe-forbidden-success.svg)](https://github.com/rust-secure-code/safety-dance/) //! [![pipeline status](https://gitlab.com/leonhard-llc/safina-rs/badges/main/pipeline.svg)](https://gitlab.com/leonhard-llc/safina-rs/-/pipelines) //! //! A threadpool. //! //! You can use it alone or with [`safina`](https://crates.io/crates/safina), //! a safe async runtime. //! //! # Features //! - Add closures or `FnOnce` to the pool //! - One of the pool's threads will execute it //! - Automatically rstarts panicked threads //! - `forbid(unsafe_code)` //! - Depends only on `std` //! - 100% test coverage //! //! # Limitations //! - Allocates memory //! - Not optimized //! //! # Documentation //! <https://docs.rs/safina-threadpool> //! //! # Examples //! ```rust //! # type ProcessResult = (); //! # fn process_data(data: (), sender: std::sync::mpsc::Sender<ProcessResult>) -> ProcessResult { //! # sender.send(()).unwrap(); //! # } //! # fn f() { //! # let data_source = vec![(),()]; //! let pool = //! safina_threadpool::ThreadPool::new("worker", 2); //! let receiver = { //! let (sender, receiver) = //! std::sync::mpsc::channel(); //! for data in data_source { //! let sender_clone = sender.clone(); //! pool.schedule( //! move || process_data(data, sender_clone)); //! } //! receiver //! }; //! let results: Vec<ProcessResult> = //! receiver.iter().collect(); //! // ... //! # } //! ``` //! //! # Alternatives //! - [`blocking`](https://crates.io/crates/blocking) //! - Popular //! - A little `unsafe` code //! - [`threadpool`](https://crates.io/crates/threadpool) //! - Popular //! - Well maintained //! - Dependencies have `unsafe` code //! - [`futures-executor`](https://crates.io/crates/futures-executor) //! - Very popular //! - Full of `unsafe` //! - [`scoped_threadpool`](https://crates.io/crates/scoped_threadpool) //! - Popular //! - Contains `unsafe` code //! - [`scheduled-thread-pool`](https://crates.io/crates/scheduled-thread-pool) //! - Used by a popular connection pool library //! - Dependencies have `unsafe` code //! - [`workerpool`](https://crates.io/crates/workerpool) //! - Dependencies have `unsafe` code //! - [`threads_pool`](https://crates.io/crates/threads_pool) //! - Full of `unsafe` //! - [`thread-pool`](https://crates.io/crates/thread-pool) //! - Old //! - Dependencies have `unsafe` code //! - [`tasque`](https://crates.io/crates/tasque) //! - Dependencies have `unsafe` code //! - [`fast-threadpool`](https://crates.io/crates/fast-threadpool) //! - Dependencies have `unsafe` code //! - [`blocking-permit`](https://crates.io/crates/blocking-permit) //! - Full of `unsafe` //! - [`rayon-core`](https://crates.io/crates/rayon-core) //! - Full of `unsafe` //! //! # Changelog //! - v0.1.3 - Support stable Rust! Needs 1.51+. //! - v0.1.2 - Add another example //! - v0.1.1 - Simplified internals and improved documentation. //! - v0.1.0 - First release //! //! # TO DO //! - DONE - Add `schedule` and `try_schedule` //! - DONE - Add tests //! - DONE - Add docs //! - DONE - Publish on crates.io //! - Add a stress test //! - Add a benchmark. See benchmarks in <https://crates.io/crates/executors> //! - Add a way for a job to schedule another job on the same thread, with stealing. //! //! # Release Process //! 1. Edit `Cargo.toml` and bump version number. //! 1. Run `./release.sh` #![forbid(unsafe_code)] #[cfg(test)] mod tests; use core::fmt::{Display, Formatter}; use core::sync::atomic::{AtomicUsize, Ordering}; use core::time::Duration; use std::error::Error; use std::sync::mpsc::{Receiver, RecvTimeoutError, SyncSender, TrySendError}; use std::sync::{Arc, Mutex}; struct AtomicCounter { next_value: AtomicUsize, } impl AtomicCounter { pub fn new() -> Self { Self { next_value: AtomicUsize::new(0), } } pub fn next(&self) -> usize { self.next_value.fetch_add(1, Ordering::AcqRel) } } /// Returned by [`try_schedule`](struct.ThreadPool.html#method.try_schedule) /// when the queue is full. /// This can happen when the program schedules many closures at one time. /// It can also happen when closures panic their threads. The pool's /// throughput goes down when it must create new threads. #[derive(Debug)] pub struct QueueFull {} impl Display for QueueFull { fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), std::fmt::Error> { std::fmt::Debug::fmt(self, f) } } impl Error for QueueFull {} struct Inner { name: &'static str, next_name_num: AtomicCounter, size: usize, receiver: Mutex<Receiver<Box<dyn FnOnce() + Send>>>, } impl Inner { pub fn num_live_threads(self: &Arc<Inner>) -> usize { Arc::strong_count(self) - 1 } fn work(self: &Arc<Inner>) { loop { let recv_result = self .receiver .lock() .unwrap() .recv_timeout(Duration::from_millis(500)); self.start_threads(); match recv_result { Ok(f) => f(), Err(RecvTimeoutError::Timeout) => {} // ThreadPool was dropped. Err(RecvTimeoutError::Disconnected) => return, }; self.start_threads(); } } fn start_thread(self: &Arc<Inner>) { let self_clone = self.clone(); if self.num_live_threads() <= self.size { std::thread::Builder::new() .name(format!("{}{}", self.name, self.next_name_num.next())) .spawn(move || self_clone.work()) .unwrap(); } } fn start_threads(self: &Arc<Inner>) { while self.num_live_threads() < self.size { self.start_thread(); } } } /// A collection of threads and a queue for jobs (`FnOnce` structs) they execute. /// /// Threads die when they execute a job that panics. /// If one thread survives, it will recreate all the threads. /// The next call to [`schedule`](#method.schedule) or [`try_schedule`](#method.try_schedule) /// also recreates threads. /// /// If your threadpool load is bursty and you want to automatically recover /// from an all-threads-panicked state, you could use /// [`safina_timer`](https://crates.io/crates/safina-timer) to periodically call /// [`schedule`](#method.schedule) or [`try_schedule`](#method.try_schedule). /// /// # Example /// ```rust /// # type ProcessResult = (); /// # fn process_data(data: (), sender: std::sync::mpsc::Sender<ProcessResult>) -> ProcessResult { /// # sender.send(()).unwrap(); /// # } /// # fn f() { /// # let data_source = vec![(),()]; /// let pool = /// safina_threadpool::ThreadPool::new("worker", 2); /// let receiver = { /// let (sender, receiver) = /// std::sync::mpsc::channel(); /// for data in data_source { /// let sender_clone = sender.clone(); /// pool.schedule( /// move || process_data(data, sender_clone)); /// } /// receiver /// }; /// let results: Vec<ProcessResult> = /// receiver.iter().collect(); /// // ... /// # } /// ``` /// /// ```rust /// # use core::time::Duration; /// # use std::sync::Arc; /// let pool = /// Arc::new(safina_threadpool::ThreadPool::new("worker", 2)); /// let executor = safina_executor::Executor::default(); /// safina_timer::start_timer_thread(); /// let pool_clone = pool.clone(); /// executor.spawn(async move { /// loop { /// safina_timer::sleep_for(Duration::from_millis(500)).await; /// pool_clone.schedule(|| {}); /// } /// }); /// # assert_eq!(2, pool.num_live_threads()); /// # for _ in 0..2 { /// # pool.schedule(|| { /// # std::thread::sleep(Duration::from_millis(100)); /// # panic!("ignore this panic") /// # }); /// # } /// # std::thread::sleep(Duration::from_millis(200)); /// # assert_eq!(0, pool.num_live_threads()); /// # std::thread::sleep(Duration::from_millis(500)); /// # assert_eq!(2, pool.num_live_threads()); /// ``` pub struct ThreadPool { inner: Arc<Inner>, sender: SyncSender<Box<dyn FnOnce() + Send>>, } impl ThreadPool { /// Creates a new thread pool containing `size` threads. /// The threads all start immediately. /// /// Threads are named with `name` with a number. /// For example, `ThreadPool::new("worker", 2)` /// creates threads named "worker-1" and "worker-2". /// If one of those threads panics, the pool creates "worker-3". /// /// After the `ThreadPool` struct drops, the threads continue processing /// jobs and stop when the queue is empty. /// /// # Panics /// Panics if `name` is empty or `size` is zero. #[must_use] pub fn new(name: &'static str, size: usize) -> Self { if name.is_empty() { panic!("ThreadPool::new called with empty name") } if size < 1 { panic!("ThreadPool::new called with invalid size value: {:?}", size) } // Use a channel with bounded size. // If the channel was unbounded, the process could OOM when throughput goes down. let (sender, receiver) = std::sync::mpsc::sync_channel(size * 200); let pool = ThreadPool { inner: Arc::new(Inner { name, next_name_num: AtomicCounter::new(), size, receiver: Mutex::new(receiver), }), sender, }; pool.inner.start_threads(); pool } /// Returns the number of threads in the pool. #[must_use] pub fn size(&self) -> usize { self.inner.size } /// Returns the number of threads currently alive. #[must_use] pub fn num_live_threads(&self) -> usize { self.inner.num_live_threads() } /// Adds a job to the queue. The next idle thread will execute it. /// Jobs are started in FIFO order. /// /// Blocks when the queue is full. /// See [`try_schedule`](#method.try_schedule). /// /// Recreates any threads that panicked. /// /// Puts `f` in a [`Box`](https://doc.rust-lang.org/stable/std/boxed/struct.Box.html) before /// adding it to the queue. #[allow(clippy::missing_panics_doc)] pub fn schedule(&self, f: impl FnOnce() + Send + 'static) { // If all workers panicked and the queue is full, adding to the queue will // block forever. So we start threads first. self.inner.start_threads(); self.sender.send(Box::new(f)).unwrap(); } /// Adds a job to the queue. The next idle thread will execute it. /// Jobs are started in FIFO order. /// /// Recreates any threads that panicked. /// /// Puts `f` in a [`Box`](https://doc.rust-lang.org/stable/std/boxed/struct.Box.html) before /// adding it to the queue. /// /// # Errors /// Returns `Err(QueueFull)` when the queue is full. pub fn try_schedule(&self, f: impl FnOnce() + Send + 'static) -> Result<(), QueueFull> { let result = match self.sender.try_send(Box::new(f)) { Ok(_) => Ok(()), Err(TrySendError::Disconnected(_)) => unreachable!(), Err(TrySendError::Full(_)) => Err(QueueFull {}), }; self.inner.start_threads(); result } }