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
//! [![Documentation](https://img.shields.io/badge/docs-0.7.0-4d76ae?style=for-the-badge)](https://docs.rs/awaitgroup/0.7.0)
//! [![Version](https://img.shields.io/crates/v/awaitgroup?style=for-the-badge)](https://crates.io/crates/awaitgroup)
//! [![License](https://img.shields.io/crates/l/awaitgroup?style=for-the-badge)](https://crates.io/crates/awaitgroup)
//! [![Actions](https://img.shields.io/github/workflow/status/ibraheemdev/awaitgroup/Rust/master?style=for-the-badge)](https://github.com/ibraheemdev/awaitgroup/actions)
//!
//! A `WaitGroup` waits for a collection of async tasks to finish.
//!
//! The main task can create new workers and pass them to each of the tasks it wants to wait for. Each of the tasks calls `done` when
//! it finishes executing, and the main task can call `wait` to block until all registered workers are done.
//!
//! # Examples
//!
//! ```rust
//! # fn main() {
//! # let rt = tokio::runtime::Builder::new_current_thread().build().unwrap();
//! # rt.block_on(async {
//! use awaitgroup::WaitGroup;
//!
//! let mut wg = WaitGroup::new();
//!
//! for _ in 0..5 {
//! // Create a new worker.
//! let worker = wg.worker();
//!
//! tokio::spawn(async {
//! // Do some work...
//!
//! // This task is done all of its work.
//! worker.done();
//! });
//! }
//!
//! // Block until all other tasks have finished their work.
//! wg.wait().await;
//! # });
//! # }
//! ```
//!
//! A `WaitGroup` can be re-used and awaited multiple times.
//!
//! ```rust
//! # use awaitgroup::WaitGroup;
//! # fn main() {
//! # let rt = tokio::runtime::Builder::new_current_thread().build().unwrap();
//! # rt.block_on(async {
//! let mut wg = WaitGroup::new();
//!
//! let worker = wg.worker();
//!
//! tokio::spawn(async {
//! // Do work...
//! worker.done();
//! });
//!
//! // Wait for tasks to finish
//! wg.wait().await;
//!
//! // Re-use wait group
//! let worker = wg.worker();
//!
//! tokio::spawn(async {
//! // Do more work...
//! worker.done();
//! });
//!
//! wg.wait().await;
//! # });
//! # }
//! ```
#![deny(missing_debug_implementations, rust_2018_idioms)]
use std::fmt;
use std::future::Future;
use std::pin::Pin;
use std::sync::atomic::{AtomicUsize, Ordering};
use std::sync::{Arc, Mutex};
use std::task::{Context, Poll, Waker};
/// Wait for a collection of tasks to finish execution.
///
/// Refer to the [crate level documentation](crate) for details.
pub struct WaitGroup {
inner: Arc<Inner>,
}
impl Default for WaitGroup {
fn default() -> Self {
Self {
inner: Arc::new(Inner::new()),
}
}
}
impl WaitGroup {
/// Creates a new `WaitGroup`.
pub fn new() -> Self {
Self::default()
}
/// Register a new worker.
pub fn worker(&self) -> Worker {
self.inner.count.fetch_add(1, Ordering::Relaxed);
Worker {
inner: self.inner.clone(),
}
}
/// Wait until all registered workers finish executing.
pub async fn wait(&mut self) {
WaitGroupFuture::new(&self.inner).await
}
}
struct WaitGroupFuture<'a> {
inner: &'a Arc<Inner>,
}
impl<'a> WaitGroupFuture<'a> {
fn new(inner: &'a Arc<Inner>) -> Self {
Self { inner }
}
}
impl Future for WaitGroupFuture<'_> {
type Output = ();
fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
if self.inner.count.load(Ordering::Relaxed) == 0 {
return Poll::Ready(());
}
let waker = cx.waker().clone();
*self.inner.waker.lock().unwrap() = Some(waker);
match self.inner.count.load(Ordering::Relaxed) {
0 => Poll::Ready(()),
_ => Poll::Pending,
}
}
}
struct Inner {
waker: Mutex<Option<Waker>>,
count: AtomicUsize,
}
impl Inner {
pub fn new() -> Self {
Self {
count: AtomicUsize::new(0),
waker: Mutex::new(None),
}
}
}
/// A worker registered in a `WaitGroup`.
///
/// Refer to the [crate level documentation](crate) for details.
pub struct Worker {
inner: Arc<Inner>,
}
impl Worker {
/// Notify the `WaitGroup` that this worker has finished execution.
pub fn done(self) {
drop(self)
}
}
impl Clone for Worker {
/// Cloning a worker increments the primary reference count and returns a new worker for use in
/// another task.
fn clone(&self) -> Self {
self.inner.count.fetch_add(1, Ordering::Relaxed);
Self {
inner: self.inner.clone(),
}
}
}
impl Drop for Worker {
fn drop(&mut self) {
let count = self.inner.count.fetch_sub(1, Ordering::Relaxed);
// We are the last worker
if count == 1 {
if let Some(waker) = self.inner.waker.lock().unwrap().take() {
waker.wake();
}
}
}
}
impl fmt::Debug for WaitGroup {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
let count = self.inner.count.load(Ordering::Relaxed);
f.debug_struct("WaitGroup").field("count", &count).finish()
}
}
impl fmt::Debug for Worker {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
let count = self.inner.count.load(Ordering::Relaxed);
f.debug_struct("Worker").field("count", &count).finish()
}
}
#[cfg(test)]
mod tests {
use super::*;
use std::time::Duration;
#[test]
fn test_wait_group() {
let rt = tokio::runtime::Builder::new_current_thread()
.build()
.unwrap();
rt.block_on(async {
let mut wg = WaitGroup::new();
for _ in 0..5 {
let worker = wg.worker();
tokio::spawn(async {
tokio::time::sleep(Duration::from_secs(5)).await;
worker.done();
});
}
wg.wait().await;
});
}
#[test]
fn test_wait_group_reuse() {
let rt = tokio::runtime::Builder::new_current_thread()
.build()
.unwrap();
rt.block_on(async {
let mut wg = WaitGroup::new();
for _ in 0..5 {
let worker = wg.worker();
tokio::spawn(async {
tokio::time::sleep(Duration::from_secs(5)).await;
worker.done();
});
}
wg.wait().await;
let worker = wg.worker();
tokio::spawn(async {
tokio::time::sleep(Duration::from_secs(5)).await;
worker.done();
});
wg.wait().await;
});
}
#[test]
fn test_worker_clone() {
let rt = tokio::runtime::Builder::new_current_thread()
.build()
.unwrap();
rt.block_on(async {
let mut wg = WaitGroup::new();
for _ in 0..5 {
let worker = wg.worker();
tokio::spawn(async {
let nested_worker = worker.clone();
tokio::spawn(async {
nested_worker.done();
});
worker.done();
});
}
wg.wait().await;
});
}
}