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 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581
//! The Tokio runtime. //! //! Unlike other Rust programs, asynchronous applications require //! runtime support. In particular, the following runtime services are //! necessary: //! //! * An **I/O event loop**, called the driver, which drives I/O resources and //! dispatches I/O events to tasks that depend on them. //! * A **scheduler** to execute [tasks] that use these I/O resources. //! * A **timer** for scheduling work to run after a set period of time. //! //! Tokio's [`Runtime`] bundles all of these services as a single type, allowing //! them to be started, shut down, and configured together. However, most //! applications won't need to use [`Runtime`] directly. Instead, they can //! use the [`tokio::main`] attribute macro, which creates a [`Runtime`] under //! the hood. //! //! # Usage //! //! Most applications will use the [`tokio::main`] attribute macro. //! //! ```no_run //! use tokio::net::TcpListener; //! use tokio::prelude::*; //! //! #[tokio::main] //! async fn main() -> Result<(), Box<dyn std::error::Error>> { //! let mut listener = TcpListener::bind("127.0.0.1:8080").await?; //! //! loop { //! let (mut socket, _) = listener.accept().await?; //! //! tokio::spawn(async move { //! let mut buf = [0; 1024]; //! //! // In a loop, read data from the socket and write the data back. //! loop { //! let n = match socket.read(&mut buf).await { //! // socket closed //! Ok(n) if n == 0 => return, //! Ok(n) => n, //! Err(e) => { //! println!("failed to read from socket; err = {:?}", e); //! return; //! } //! }; //! //! // Write the data back //! if let Err(e) = socket.write_all(&buf[0..n]).await { //! println!("failed to write to socket; err = {:?}", e); //! return; //! } //! } //! }); //! } //! } //! ``` //! //! From within the context of the runtime, additional tasks are spawned using //! the [`tokio::spawn`] function. Futures spawned using this function will be //! executed on the same thread pool used by the [`Runtime`]. //! //! A [`Runtime`] instance can also be used directly. //! //! ```no_run //! use tokio::net::TcpListener; //! use tokio::prelude::*; //! use tokio::runtime::Runtime; //! //! fn main() -> Result<(), Box<dyn std::error::Error>> { //! // Create the runtime //! let mut rt = Runtime::new()?; //! //! // Spawn the root task //! rt.block_on(async { //! let mut listener = TcpListener::bind("127.0.0.1:8080").await?; //! //! loop { //! let (mut socket, _) = listener.accept().await?; //! //! tokio::spawn(async move { //! let mut buf = [0; 1024]; //! //! // In a loop, read data from the socket and write the data back. //! loop { //! let n = match socket.read(&mut buf).await { //! // socket closed //! Ok(n) if n == 0 => return, //! Ok(n) => n, //! Err(e) => { //! println!("failed to read from socket; err = {:?}", e); //! return; //! } //! }; //! //! // Write the data back //! if let Err(e) = socket.write_all(&buf[0..n]).await { //! println!("failed to write to socket; err = {:?}", e); //! return; //! } //! } //! }); //! } //! }) //! } //! ``` //! //! ## Runtime Configurations //! //! Tokio provides multiple task scheduling strategies, suitable for different //! applications. The [runtime builder] or `#[tokio::main]` attribute may be //! used to select which scheduler to use. //! //! #### Basic Scheduler //! //! The basic scheduler provides a _single-threaded_ future executor. All tasks //! will be created and executed on the current thread. The basic scheduler //! requires the `rt-core` feature flag, and can be selected using the //! [`Builder::basic_scheduler`] method: //! ``` //! use tokio::runtime; //! //! # fn main() -> Result<(), Box<dyn std::error::Error>> { //! let basic_rt = runtime::Builder::new() //! .basic_scheduler() //! .build()?; //! # Ok(()) } //! ``` //! //! If the `rt-core` feature is enabled and `rt-threaded` is not, //! [`Runtime::new`] will return a basic scheduler runtime by default. //! //! #### Threaded Scheduler //! //! The threaded scheduler executes futures on a _thread pool_, using a //! work-stealing strategy. By default, it will start a worker thread for each //! CPU core available on the system. This tends to be the ideal configurations //! for most applications. The threaded scheduler requires the `rt-threaded` feature //! flag, and can be selected using the [`Builder::threaded_scheduler`] method: //! ``` //! use tokio::runtime; //! //! # fn main() -> Result<(), Box<dyn std::error::Error>> { //! let threaded_rt = runtime::Builder::new() //! .threaded_scheduler() //! .build()?; //! # Ok(()) } //! ``` //! //! If the `rt-threaded` feature flag is enabled, [`Runtime::new`] will return a //! threaded scheduler runtime by default. //! //! Most applications should use the threaded scheduler, except in some niche //! use-cases, such as when running only a single thread is required. //! //! #### Resource drivers //! //! When configuring a runtime by hand, no resource drivers are enabled by //! default. In this case, attempting to use networking types or time types will //! fail. In order to enable these types, the resource drivers must be enabled. //! This is done with [`Builder::enable_io`] and [`Builder::enable_time`]. As a //! shorthand, [`Builder::enable_all`] enables both resource drivers. //! //! ## Lifetime of spawned threads //! //! The runtime may spawn threads depending on its configuration and usage. The //! threaded scheduler spawns threads to schedule tasks and calls to //! `spawn_blocking` spawn threads to run blocking operations. //! //! While the `Runtime` is active, threads may shutdown after periods of being //! idle. Once `Runtime` is dropped, all runtime threads are forcibly shutdown. //! Any tasks that have not yet completed will be dropped. //! //! [tasks]: crate::task //! [`Runtime`]: Runtime //! [`tokio::spawn`]: crate::spawn //! [`tokio::main`]: ../attr.main.html //! [runtime builder]: crate::runtime::Builder //! [`Runtime::new`]: crate::runtime::Runtime::new //! [`Builder::basic_scheduler`]: crate::runtime::Builder::basic_scheduler //! [`Builder::threaded_scheduler`]: crate::runtime::Builder::threaded_scheduler //! [`Builder::enable_io`]: crate::runtime::Builder::enable_io //! [`Builder::enable_time`]: crate::runtime::Builder::enable_time //! [`Builder::enable_all`]: crate::runtime::Builder::enable_all // At the top due to macros #[cfg(test)] #[macro_use] mod tests; pub(crate) mod context; cfg_rt_core! { mod basic_scheduler; use basic_scheduler::BasicScheduler; pub(crate) mod task; } mod blocking; use blocking::BlockingPool; cfg_blocking_impl! { #[allow(unused_imports)] pub(crate) use blocking::{spawn_blocking, try_spawn_blocking}; } mod builder; pub use self::builder::Builder; pub(crate) mod enter; use self::enter::enter; mod handle; pub use self::handle::{Handle, TryCurrentError}; mod io; cfg_rt_threaded! { mod park; use park::Parker; } mod shell; use self::shell::Shell; mod spawner; use self::spawner::Spawner; mod time; cfg_rt_threaded! { mod queue; pub(crate) mod thread_pool; use self::thread_pool::ThreadPool; } cfg_rt_core! { use crate::task::JoinHandle; } use std::future::Future; use std::time::Duration; /// The Tokio runtime. /// /// The runtime provides an I/O driver, task scheduler, [timer], and blocking /// pool, necessary for running asynchronous tasks. /// /// Instances of `Runtime` can be created using [`new`] or [`Builder`]. However, /// most users will use the `#[tokio::main]` annotation on their entry point instead. /// /// See [module level][mod] documentation for more details. /// /// # Shutdown /// /// Shutting down the runtime is done by dropping the value. The current thread /// will block until the shut down operation has completed. /// /// * Drain any scheduled work queues. /// * Drop any futures that have not yet completed. /// * Drop the reactor. /// /// Once the reactor has dropped, any outstanding I/O resources bound to /// that reactor will no longer function. Calling any method on them will /// result in an error. /// /// [timer]: crate::time /// [mod]: index.html /// [`new`]: method@Self::new /// [`Builder`]: struct@Builder /// [`tokio::run`]: fn@run #[derive(Debug)] pub struct Runtime { /// Task executor kind: Kind, /// Handle to runtime, also contains driver handles handle: Handle, /// Blocking pool handle, used to signal shutdown blocking_pool: BlockingPool, } /// The runtime executor is either a thread-pool or a current-thread executor. #[derive(Debug)] enum Kind { /// Not able to execute concurrent tasks. This variant is mostly used to get /// access to the driver handles. Shell(Shell), /// Execute all tasks on the current-thread. #[cfg(feature = "rt-core")] Basic(BasicScheduler<time::Driver>), /// Execute tasks across multiple threads. #[cfg(feature = "rt-threaded")] ThreadPool(ThreadPool), } /// After thread starts / before thread stops type Callback = std::sync::Arc<dyn Fn() + Send + Sync>; impl Runtime { /// Create a new runtime instance with default configuration values. /// /// This results in a scheduler, I/O driver, and time driver being /// initialized. The type of scheduler used depends on what feature flags /// are enabled: if the `rt-threaded` feature is enabled, the [threaded /// scheduler] is used, while if only the `rt-core` feature is enabled, the /// [basic scheduler] is used instead. /// /// If the threaded scheduler is selected, it will not spawn /// any worker threads until it needs to, i.e. tasks are scheduled to run. /// /// Most applications will not need to call this function directly. Instead, /// they will use the [`#[tokio::main]` attribute][main]. When more complex /// configuration is necessary, the [runtime builder] may be used. /// /// See [module level][mod] documentation for more details. /// /// # Examples /// /// Creating a new `Runtime` with default configuration values. /// /// ``` /// use tokio::runtime::Runtime; /// /// let rt = Runtime::new() /// .unwrap(); /// /// // Use the runtime... /// ``` /// /// [mod]: index.html /// [main]: ../attr.main.html /// [threaded scheduler]: index.html#threaded-scheduler /// [basic scheduler]: index.html#basic-scheduler /// [runtime builder]: crate::runtime::Builder pub fn new() -> io::Result<Runtime> { #[cfg(feature = "rt-threaded")] let ret = Builder::new().threaded_scheduler().enable_all().build(); #[cfg(all(not(feature = "rt-threaded"), feature = "rt-core"))] let ret = Builder::new().basic_scheduler().enable_all().build(); #[cfg(not(feature = "rt-core"))] let ret = Builder::new().enable_all().build(); ret } /// Spawn a future onto the Tokio runtime. /// /// This spawns the given future onto the runtime's executor, usually a /// thread pool. The thread pool is then responsible for polling the future /// until it completes. /// /// See [module level][mod] documentation for more details. /// /// [mod]: index.html /// /// # Examples /// /// ``` /// use tokio::runtime::Runtime; /// /// # fn dox() { /// // Create the runtime /// let rt = Runtime::new().unwrap(); /// /// // Spawn a future onto the runtime /// rt.spawn(async { /// println!("now running on a worker thread"); /// }); /// # } /// ``` /// /// # Panics /// /// This function will not panic unless task execution is disabled on the /// executor. This can only happen if the runtime was built using /// [`Builder`] without picking either [`basic_scheduler`] or /// [`threaded_scheduler`]. /// /// [`Builder`]: struct@Builder /// [`threaded_scheduler`]: fn@Builder::threaded_scheduler /// [`basic_scheduler`]: fn@Builder::basic_scheduler #[cfg(feature = "rt-core")] pub fn spawn<F>(&self, future: F) -> JoinHandle<F::Output> where F: Future + Send + 'static, F::Output: Send + 'static, { match &self.kind { Kind::Shell(_) => panic!("task execution disabled"), #[cfg(feature = "rt-threaded")] Kind::ThreadPool(exec) => exec.spawn(future), Kind::Basic(exec) => exec.spawn(future), } } /// Run a future to completion on the Tokio runtime. This is the runtime's /// entry point. /// /// This runs the given future on the runtime, blocking until it is /// complete, and yielding its resolved result. Any tasks or timers which /// the future spawns internally will be executed on the runtime. /// /// `&mut` is required as calling `block_on` **may** result in advancing the /// state of the runtime. The details depend on how the runtime is /// configured. [`runtime::Handle::block_on`][handle] provides a version /// that takes `&self`. /// /// This method may not be called from an asynchronous context. /// /// # Panics /// /// This function panics if the provided future panics, or if called within an /// asynchronous execution context. /// /// # Examples /// /// ```no_run /// use tokio::runtime::Runtime; /// /// // Create the runtime /// let mut rt = Runtime::new().unwrap(); /// /// // Execute the future, blocking the current thread until completion /// rt.block_on(async { /// println!("hello"); /// }); /// ``` /// /// [handle]: fn@Handle::block_on pub fn block_on<F: Future>(&mut self, future: F) -> F::Output { let kind = &mut self.kind; self.handle.enter(|| match kind { Kind::Shell(exec) => exec.block_on(future), #[cfg(feature = "rt-core")] Kind::Basic(exec) => exec.block_on(future), #[cfg(feature = "rt-threaded")] Kind::ThreadPool(exec) => exec.block_on(future), }) } /// Enter the runtime context. This allows you to construct types that must /// have an executor available on creation such as [`Delay`] or [`TcpStream`]. /// It will also allow you to call methods such as [`tokio::spawn`]. /// /// This function is also available as [`Handle::enter`]. /// /// [`Delay`]: struct@crate::time::Delay /// [`TcpStream`]: struct@crate::net::TcpStream /// [`Handle::enter`]: fn@crate::runtime::Handle::enter /// [`tokio::spawn`]: fn@crate::spawn /// /// # Example /// /// ``` /// use tokio::runtime::Runtime; /// /// fn function_that_spawns(msg: String) { /// // Had we not used `rt.enter` below, this would panic. /// tokio::spawn(async move { /// println!("{}", msg); /// }); /// } /// /// fn main() { /// let rt = Runtime::new().unwrap(); /// /// let s = "Hello World!".to_string(); /// /// // By entering the context, we tie `tokio::spawn` to this executor. /// rt.enter(|| function_that_spawns(s)); /// } /// ``` pub fn enter<F, R>(&self, f: F) -> R where F: FnOnce() -> R, { self.handle.enter(f) } /// Return a handle to the runtime's spawner. /// /// The returned handle can be used to spawn tasks that run on this runtime, and can /// be cloned to allow moving the `Handle` to other threads. /// /// # Examples /// /// ``` /// use tokio::runtime::Runtime; /// /// let rt = Runtime::new() /// .unwrap(); /// /// let handle = rt.handle(); /// /// handle.spawn(async { println!("hello"); }); /// ``` pub fn handle(&self) -> &Handle { &self.handle } /// Shutdown the runtime, waiting for at most `duration` for all spawned /// task to shutdown. /// /// Usually, dropping a `Runtime` handle is sufficient as tasks are able to /// shutdown in a timely fashion. However, dropping a `Runtime` will wait /// indefinitely for all tasks to terminate, and there are cases where a long /// blocking task has been spawned, which can block dropping `Runtime`. /// /// In this case, calling `shutdown_timeout` with an explicit wait timeout /// can work. The `shutdown_timeout` will signal all tasks to shutdown and /// will wait for at most `duration` for all spawned tasks to terminate. If /// `timeout` elapses before all tasks are dropped, the function returns and /// outstanding tasks are potentially leaked. /// /// # Examples /// /// ``` /// use tokio::runtime::Runtime; /// use tokio::task; /// /// use std::thread; /// use std::time::Duration; /// /// fn main() { /// let mut runtime = Runtime::new().unwrap(); /// /// runtime.block_on(async move { /// task::spawn_blocking(move || { /// thread::sleep(Duration::from_secs(10_000)); /// }); /// }); /// /// runtime.shutdown_timeout(Duration::from_millis(100)); /// } /// ``` pub fn shutdown_timeout(self, duration: Duration) { let Runtime { mut blocking_pool, .. } = self; blocking_pool.shutdown(Some(duration)); } /// Shutdown the runtime, without waiting for any spawned tasks to shutdown. /// /// This can be useful if you want to drop a runtime from within another runtime. /// Normally, dropping a runtime will block indefinitely for spawned blocking tasks /// to complete, which would normally not be permitted within an asynchronous context. /// By calling `shutdown_background()`, you can drop the runtime from such a context. /// /// Note however, that because we do not wait for any blocking tasks to complete, this /// may result in a resource leak (in that any blocking tasks are still running until they /// return. /// /// This function is equivalent to calling `shutdown_timeout(Duration::of_nanos(0))`. /// /// ``` /// use tokio::runtime::Runtime; /// /// fn main() { /// let mut runtime = Runtime::new().unwrap(); /// /// runtime.block_on(async move { /// let inner_runtime = Runtime::new().unwrap(); /// // ... /// inner_runtime.shutdown_background(); /// }); /// } /// ``` pub fn shutdown_background(self) { self.shutdown_timeout(Duration::from_nanos(0)) } }