| <!DOCTYPE html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta name="generator" content="rustdoc"><meta name="description" content="Source of the Rust file `/root/.cargo/git/checkouts/tokio-377c595163f99a10/dfe252d/tokio/src/task/spawn.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>spawn.rs - source</title><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../SourceSerif4-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../FiraSans-Regular.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../FiraSans-Medium.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../SourceCodePro-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../SourceSerif4-Bold.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../SourceCodePro-Semibold.ttf.woff2"><link rel="stylesheet" href="../../../normalize.css"><link rel="stylesheet" href="../../../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" href="../../../ayu.css" disabled><link rel="stylesheet" href="../../../dark.css" disabled><link rel="stylesheet" href="../../../light.css" id="themeStyle"><script id="default-settings" ></script><script src="../../../storage.js"></script><script defer src="../../../source-script.js"></script><script defer src="../../../source-files.js"></script><script defer src="../../../main.js"></script><noscript><link rel="stylesheet" href="../../../noscript.css"></noscript><link rel="alternate icon" type="image/png" href="../../../favicon-16x16.png"><link rel="alternate icon" type="image/png" href="../../../favicon-32x32.png"><link rel="icon" type="image/svg+xml" href="../../../favicon.svg"></head><body class="rustdoc source"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><a class="sidebar-logo" href="../../../tokio/index.html"><div class="logo-container"><img class="rust-logo" src="../../../rust-logo.svg" alt="logo"></div></a></nav><main><div class="width-limiter"><nav class="sub"><a class="sub-logo-container" href="../../../tokio/index.html"><img class="rust-logo" src="../../../rust-logo.svg" alt="logo"></a><form class="search-form"><div class="search-container"><span></span><input class="search-input" name="search" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><div id="help-button" title="help" tabindex="-1"><a href="../../../help.html">?</a></div><div id="settings-menu" tabindex="-1"><a href="../../../settings.html" title="settings"><img width="22" height="22" alt="Change settings" src="../../../wheel.svg"></a></div></div></form></nav><section id="main-content" class="content"><div class="example-wrap"><pre class="src-line-numbers"><span id="1">1</span> |
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| </pre><pre class="rust"><code><span class="kw">use </span><span class="kw">crate</span>::runtime::Handle; |
| <span class="kw">use </span><span class="kw">crate</span>::task::JoinHandle; |
| |
| <span class="kw">use </span>std::future::Future; |
| |
| <span class="macro">cfg_rt! </span>{ |
| <span class="doccomment">/// Spawns a new asynchronous task, returning a |
| /// [`JoinHandle`](super::JoinHandle) for it. |
| /// |
| /// You do not have to `.await` the returned `JoinHandle` to make the |
| /// provided future start execution. It will start running in the background |
| /// immediately when `spawn` is called. |
| /// |
| /// Spawning a task enables the task to execute concurrently to other tasks. The |
| /// spawned task may execute on the current thread, or it may be sent to a |
| /// different thread to be executed. The specifics depend on the current |
| /// [`Runtime`](crate::runtime::Runtime) configuration. |
| /// |
| /// There is no guarantee that a spawned task will execute to completion. |
| /// When a runtime is shutdown, all outstanding tasks are dropped, |
| /// regardless of the lifecycle of that task. |
| /// |
| /// This function must be called from the context of a Tokio runtime. Tasks running on |
| /// the Tokio runtime are always inside its context, but you can also enter the context |
| /// using the [`Runtime::enter`](crate::runtime::Runtime::enter()) method. |
| /// |
| /// # Examples |
| /// |
| /// In this example, a server is started and `spawn` is used to start a new task |
| /// that processes each received connection. |
| /// |
| /// ```no_run |
| /// use tokio::net::{TcpListener, TcpStream}; |
| /// |
| /// use std::io; |
| /// |
| /// async fn process(socket: TcpStream) { |
| /// // ... |
| /// # drop(socket); |
| /// } |
| /// |
| /// #[tokio::main] |
| /// async fn main() -> io::Result<()> { |
| /// let listener = TcpListener::bind("127.0.0.1:8080").await?; |
| /// |
| /// loop { |
| /// let (socket, _) = listener.accept().await?; |
| /// |
| /// tokio::spawn(async move { |
| /// // Process each socket concurrently. |
| /// process(socket).await |
| /// }); |
| /// } |
| /// } |
| /// ``` |
| /// |
| /// To run multiple tasks in parallel and receive their results, join |
| /// handles can be stored in a vector. |
| /// ``` |
| /// # #[tokio::main(flavor = "current_thread")] async fn main() { |
| /// async fn my_background_op(id: i32) -> String { |
| /// let s = format!("Starting background task {}.", id); |
| /// println!("{}", s); |
| /// s |
| /// } |
| /// |
| /// let ops = vec![1, 2, 3]; |
| /// let mut tasks = Vec::with_capacity(ops.len()); |
| /// for op in ops { |
| /// // This call will make them start running in the background |
| /// // immediately. |
| /// tasks.push(tokio::spawn(my_background_op(op))); |
| /// } |
| /// |
| /// let mut outputs = Vec::with_capacity(tasks.len()); |
| /// for task in tasks { |
| /// outputs.push(task.await.unwrap()); |
| /// } |
| /// println!("{:?}", outputs); |
| /// # } |
| /// ``` |
| /// This example pushes the tasks to `outputs` in the order they were |
| /// started in. If you do not care about the ordering of the outputs, then |
| /// you can also use a [`JoinSet`]. |
| /// |
| /// [`JoinSet`]: struct@crate::task::JoinSet |
| /// |
| /// # Panics |
| /// |
| /// Panics if called from **outside** of the Tokio runtime. |
| /// |
| /// # Using `!Send` values from a task |
| /// |
| /// The task supplied to `spawn` must implement `Send`. However, it is |
| /// possible to **use** `!Send` values from the task as long as they only |
| /// exist between calls to `.await`. |
| /// |
| /// For example, this will work: |
| /// |
| /// ``` |
| /// use tokio::task; |
| /// |
| /// use std::rc::Rc; |
| /// |
| /// fn use_rc(rc: Rc<()>) { |
| /// // Do stuff w/ rc |
| /// # drop(rc); |
| /// } |
| /// |
| /// #[tokio::main] |
| /// async fn main() { |
| /// tokio::spawn(async { |
| /// // Force the `Rc` to stay in a scope with no `.await` |
| /// { |
| /// let rc = Rc::new(()); |
| /// use_rc(rc.clone()); |
| /// } |
| /// |
| /// task::yield_now().await; |
| /// }).await.unwrap(); |
| /// } |
| /// ``` |
| /// |
| /// This will **not** work: |
| /// |
| /// ```compile_fail |
| /// use tokio::task; |
| /// |
| /// use std::rc::Rc; |
| /// |
| /// fn use_rc(rc: Rc<()>) { |
| /// // Do stuff w/ rc |
| /// # drop(rc); |
| /// } |
| /// |
| /// #[tokio::main] |
| /// async fn main() { |
| /// tokio::spawn(async { |
| /// let rc = Rc::new(()); |
| /// |
| /// task::yield_now().await; |
| /// |
| /// use_rc(rc.clone()); |
| /// }).await.unwrap(); |
| /// } |
| /// ``` |
| /// |
| /// Holding on to a `!Send` value across calls to `.await` will result in |
| /// an unfriendly compile error message similar to: |
| /// |
| /// ```text |
| /// `[... some type ...]` cannot be sent between threads safely |
| /// ``` |
| /// |
| /// or: |
| /// |
| /// ```text |
| /// error[E0391]: cycle detected when processing `main` |
| /// ``` |
| </span><span class="attribute">#[track_caller] |
| </span><span class="kw">pub fn </span>spawn<T>(future: T) -> JoinHandle<T::Output> |
| <span class="kw">where |
| </span>T: Future + Send + <span class="lifetime">'static</span>, |
| T::Output: Send + <span class="lifetime">'static</span>, |
| { |
| <span class="comment">// preventing stack overflows on debug mode, by quickly sending the |
| // task to the heap. |
| </span><span class="kw">if </span><span class="macro">cfg!</span>(debug_assertions) && std::mem::size_of::<T>() > <span class="number">2048 </span>{ |
| spawn_inner(Box::pin(future), <span class="prelude-val">None</span>) |
| } <span class="kw">else </span>{ |
| spawn_inner(future, <span class="prelude-val">None</span>) |
| } |
| } |
| |
| <span class="attribute">#[track_caller] |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>spawn_inner<T>(future: T, name: <span class="prelude-ty">Option</span><<span class="kw-2">&</span>str>) -> JoinHandle<T::Output> |
| <span class="kw">where |
| </span>T: Future + Send + <span class="lifetime">'static</span>, |
| T::Output: Send + <span class="lifetime">'static</span>, |
| { |
| <span class="kw">use </span><span class="kw">crate</span>::runtime::task; |
| <span class="kw">let </span>id = task::Id::next(); |
| <span class="kw">let </span>task = <span class="kw">crate</span>::util::trace::task(future, <span class="string">"task"</span>, name, id.as_u64()); |
| <span class="kw">let </span>handle = Handle::current(); |
| handle.inner.spawn(task, id) |
| } |
| } |
| </code></pre></div> |
| </section></div></main><div id="rustdoc-vars" data-root-path="../../../" data-current-crate="tokio" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |
