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 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469
//! This crate provides a lock-free Pub/Sub event-bus inspired by the LMAX Disruptor. //! //! Users can configure how publishers handle slow subscribers through `WaitStrategy` //! policies. //! //! Both sync and async APIs are available. //! //! # Examples //! //! Please use the provided [example programs](https://github.com/sachanganesh/eventador-rs/tree/main/examples) //! for a more thorough approach on how to use this crate. //! //! Basic sync usage: //! //! ``` //! use eventador::Eventador; //! let eventbus = Eventador::new(4).unwrap(); //! let subscriber = eventbus.subscribe::<usize>(); //! //! let i: usize = 1234; //! eventbus.publish(i); //! //! let mut publisher = eventbus.publisher(); //! publisher.send(i + 1111); //! //! let mut msg = subscriber.recv(); //! assert_eq!(i, *msg); //! //! msg = subscriber.recv(); //! assert_eq!(i + 1111, *msg); //! ``` //! //! Basic async usage: //! //! ```ignore //! use eventador::{Eventador, SinkExt, StreamExt}; //! let eventbus = Eventador::new(4).unwrap(); //! //! let mut subscriber = eventador.async_subscriber::<usize>(); //! let mut publisher = eventador.async_publisher::<usize>(4); //! //! let i: usize = 1234; //! publisher.send(i).await?; //! //! let msg = subscriber.next().await?; //! assert_eq!(i, *msg); //! ``` //! //! ## Why? //! //! Event-buses ease the development burden of concurrent programs by enabling concurrent //! application subroutines to interact and affect other subroutines through events. //! //! Eventador embraces the Rust model of *Choose Your Guarantees ™* by offering different //! policies for publishing when subscribers are lagging. These are represented as //! [WaitStrategies](https://docs.rs/eventador/latest/eventador/enum.WaitStrategy), with the //! default being to wait for all subscribers to read an event before it is overwritten. //! //! ## Design Considerations //! //! A general overview of the architecture of the library can be found //! [here](https://github.com/sachanganesh/eventador-rs/blob/main/ARCHITECTURE.md). //! //! ### Ring Buffer //! //! Like Eventador, most event-bus implementations use some form of ring buffer for the underlying //! data structure to store published events. As such, an Eventador instance cannot indefinitely //! grow to accommodate events, unlike a `Vec`. Publishers require configurable policies to decide //! how and when to overwrite old data in the ring. //! //! ### LMAX Disruptor //! //! The LMAX Disruptor serves as a basis for a lot of event-bus implementations, though the //! contemporary architecture of the Disruptor looks very different from the one presented in the //! outdated LMAX white-paper. Eventador draws from the principles of the current Disruptor //! architecture, but the similarities stop there. //! //! A sequencer atomically assigns an event to an index in the ring buffer on publishing of an //! event. //! //! Subscribers internally have their own sequencer to determine their last read event in the ring //! buffer. On receiving a subscribed message, the sequencer is atomically updated to reflect that //! it can now receive the next event. //! //! ### Lock-free //! //! Eventador has the potential to be a high-contention (aka bottlenecking) structure to a given //! concurrent program, so the implementation needs to handle contention as effectively as possible. //! Atomic CAS operations are generally faster than locking, and is the preferred approach to handle //! contention. //! //! ### TypeId //! This crate relies on the use of `TypeId` to determine what type an event is, and what types of //! events a subscriber is subscribed to. //! //! Unfortunately, due to the limitations of Rust reflection tools, an Enum will have a different //! TypeId than an Enum variant. This means that a subscriber must subscribe to the Enum type and //! ignore any variants it's not interested in that it still receives. Likewise, the publisher must //! publish events as the Enum type and not the variant in order to maintain that consistency. //! #![feature(doc_cfg)] mod alertable; mod event; mod publisher; mod ring_buffer; mod sequence; mod subscriber; mod wait_strategy; #[cfg(feature = "async")] #[doc(cfg(feature = "async"))] mod futures; #[cfg(feature = "async")] #[doc(cfg(feature = "async"))] pub use crate::futures::{AsyncPublisher, AsyncSubscriber, PublishError}; #[cfg(feature = "async")] #[doc(cfg(feature = "async"))] pub use ::futures::{SinkExt, StreamExt}; pub use event::EventRead; pub use publisher::Publisher; pub use subscriber::Subscriber; pub use wait_strategy::WaitStrategy; use crate::ring_buffer::RingBuffer; use crate::sequence::Sequence; use std::sync::Arc; /// A lock-free and thread-safe event-bus implementation. /// /// # Example /// /// Basic usage: /// /// ```ignore /// let eventbus = Eventador::new(4)?; /// let subscriber = eventbus.subscribe::<usize>(); /// /// let mut i: usize = 1234; /// eventbus.publish(i); /// /// let mut msg = subscriber.recv(); /// assert_eq!(i, *msg); /// ``` /// #[derive(Clone)] pub struct Eventador { ring: Arc<RingBuffer>, } impl Eventador { /// Creates a new Eventador event-bus. /// /// **The capacity is required to be a power of 2.** /// /// This uses the default wait-strategy of [`WaitStrategy::AllSubscribers`], which will ensure /// a publisher can't overwrite an event in the ring until all subscribers have read it. /// /// # Example /// /// Basic usage: /// /// ```ignore /// let eventbus = Eventador::new(4)?; /// ``` /// pub fn new(capacity: u64) -> anyhow::Result<Self> { Ok(Self { ring: Arc::new(RingBuffer::new(capacity, WaitStrategy::AllSubscribers)?), }) } /// Creates a new Eventador event-bus with a specific [`WaitStrategy`] for publishers. /// /// **The capacity is required to be a power of 2.** /// /// # Example /// /// Basic usage: /// /// ```ignore /// let eventbus = Eventador::new(4, WaitStrategy::AllSubscribers)?; /// ``` /// pub fn with_strategy(capacity: u64, wait_strategy: WaitStrategy) -> anyhow::Result<Self> { Ok(Self { ring: Arc::new(RingBuffer::new(capacity, wait_strategy)?), }) } /// Synchronously publish an event to the event-bus. /// /// # Example /// /// Basic usage: /// /// ```ignore /// let eventbus = Eventador::new(4)?; /// /// let i: usize = 1234; /// eventbus.publish(i); /// ``` /// pub fn publish<T: 'static + Send + Sync>(&self, message: T) { let sequence = self.ring.next(); if let Some(event_store) = self.ring.get_envelope(sequence).clone() { event_store.overwrite::<T>(sequence, message); } } /// Creates a [`Publisher`] that synchronously publishes messages on the event-bus. /// /// Although the [`Eventador::publish`] function has the exact same behavior, this handle offers /// an API that mirrors the `AsyncPublisher`. /// /// # Example /// /// Basic usage: /// /// ```ignore /// let eventbus = Eventador::new(4)?; /// let mut publisher = eventbus.publisher(); /// /// let i: usize = 1234; /// publisher.send(i); /// ``` /// pub fn publisher(&self) -> Publisher { Publisher::new(self.ring.clone()) } /// Creates a [`Subscriber`] that subscribes to an event type receives them synchronously. /// /// The [`Subscriber`] will not receive subscribed events that were published to the event-bus /// before time of subscription. It will only receive events that are published after /// time of subscription. /// /// # Example /// /// Basic usage: /// /// ```ignore /// let eventbus = Eventador::new(4)?; /// /// // subscribe first, before publishing! /// let subscriber = eventbus.subscribe::<usize>(); /// /// let mut i: usize = 1234; /// eventbus.publish(i); /// /// let mut msg = subscriber.recv(); /// assert_eq!(i, *msg); /// ``` /// pub fn subscribe<T: 'static + Send>(&self) -> Subscriber<T> { let sequence = Arc::new(Sequence::with_value(self.ring.sequencer().get() + 1)); self.ring .sequencer() .register_gating_sequence(sequence.clone()); Subscriber::new(self.ring.clone(), sequence) } /// Creates an [`AsyncPublisher`] that can publish to the event-bus asynchronously. /// /// The buffer size indicates the number of events that can be buffered until a flush is made /// to the event bus. Until events are flushed to the event bus, they are not yet published. /// /// Because events are buffered, an AsyncPublisher can only publish events of the same /// type. A new AsyncPublisher must be instantiated for events of another type. /// /// # Example /// /// Basic usage: /// /// ```ignore /// let eventbus = Eventador::new(4)?; /// let mut publisher: AsyncPublisher<usize> = eventbus.async_publisher(10); /// /// let mut i: usize = 1234; /// publisher.send(i).await?; /// ``` /// #[cfg(feature = "async")] #[doc(cfg(feature = "async"))] pub fn async_publisher<T: 'static + Send + Sync + Unpin>( &self, buffer_size: usize, ) -> AsyncPublisher<T> { AsyncPublisher::new(self.ring.clone(), buffer_size) } /// Creates an [`AsyncSubscriber`] that subscribes to an event type and receive them /// asynchronously. /// /// # Example /// /// Basic usage: /// /// ```ignore /// let eventbus = Eventador::new(4)?; /// /// let subscriber = eventbus.async_subscriber::<usize>(); /// let mut publisher: AsyncPublisher<usize> = eventbus.async_publisher(); /// /// let mut i: usize = 1234; /// publisher.send(i).await?; /// /// let mut msg = subscriber.next().await.unwrap(); /// assert_eq!(i, *msg); /// ``` /// #[cfg(feature = "async")] #[doc(cfg(feature = "async"))] pub fn async_subscriber<T: Send + Unpin>(&self) -> AsyncSubscriber<T> { let sequence = Arc::new(Sequence::with_value(self.ring.sequencer().get() + 1)); self.ring .sequencer() .register_gating_sequence(sequence.clone()); AsyncSubscriber::new(self.ring.clone(), sequence) } } impl From<RingBuffer> for Eventador { fn from(ring: RingBuffer) -> Self { Self { ring: Arc::new(ring), } } } impl From<Arc<RingBuffer>> for Eventador { fn from(ring: Arc<RingBuffer>) -> Self { Self { ring } } } #[cfg(test)] mod tests { #[cfg(feature = "async")] use crate::futures::publisher::{AsyncPublisher, PublishError}; #[cfg(feature = "async")] use futures::{ future::{AbortHandle, Abortable}, SinkExt, StreamExt, }; #[cfg(feature = "async")] use async_channel::unbounded; #[cfg(feature = "async")] use ntest::timeout; use crate::Eventador; #[test] fn publish_and_subscribe() { let res = Eventador::new(2); assert!(res.is_ok()); let eventador: Eventador = res.unwrap(); let subscriber = eventador.subscribe::<usize>(); assert_eq!(1, subscriber.sequence()); let mut i: usize = 1234; eventador.publish(i); let mut msg = subscriber.recv(); assert_eq!(i, *msg); i += 1111; let eventador2 = eventador.clone(); std::thread::spawn(move || { std::thread::sleep(std::time::Duration::from_secs(1)); eventador2.publish(i); }); msg = subscriber.recv(); assert_eq!(i, *msg); } #[async_std::test] #[timeout(5000)] #[cfg(feature = "async")] async fn async_publish() { println!("Starting test!"); let res = Eventador::new(4); assert!(res.is_ok()); let eventador: Eventador = res.unwrap(); let mut subscriber = eventador.async_subscriber::<usize>(); let mut publisher: AsyncPublisher<usize> = eventador.async_publisher(4); let (sender, mut receiver) = unbounded::<Result<usize, PublishError>>(); let mut i: usize = 1234; let mut sent = sender.send(Ok(i)).await; assert!(sent.is_ok()); let (handle, reg) = AbortHandle::new_pair(); async_std::task::spawn(Abortable::new( async move { publisher.send_all(&mut receiver).await.unwrap(); }, reg, )); let mut msg = subscriber.next().await.unwrap(); assert_eq!(i, *msg); println!("Passed part 1!"); i += 1111; let eventador2 = eventador.clone(); async_std::task::spawn(async move { async_std::task::sleep(std::time::Duration::from_secs(1)).await; eventador2.publish(i); }); msg = subscriber.next().await.unwrap(); assert_eq!(i, *msg); println!("Passed part 2!"); i += 1111; sent = sender.send(Ok(i)).await; assert!(sent.is_ok()); msg = subscriber.next().await.unwrap(); assert_eq!(i, *msg); println!("Passed part 3! Done."); handle.abort(); } #[derive(Debug, Eq, PartialEq)] enum TestEnum { SampleA, } #[test] fn enum_specific_subscription() { let res = Eventador::new(4); assert!(res.is_ok()); println!("Passed part 1!"); let eventador: Eventador = res.unwrap(); let subscriber = eventador.subscribe::<TestEnum>(); assert_eq!(1, subscriber.sequence()); println!("Passed part 2!"); eventador.publish(TestEnum::SampleA); let msg = subscriber.recv(); assert_eq!(TestEnum::SampleA, *msg); println!("Passed part 3! Done."); } }