99 lines
12 KiB
HTML
99 lines
12 KiB
HTML
<!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="API documentation for the Rust `spawn` fn in crate `tokio`."><meta name="keywords" content="rust, rustlang, rust-lang, spawn"><title>tokio::task::spawn - Rust</title><link rel="stylesheet" type="text/css" href="../../normalize.css"><link rel="stylesheet" type="text/css" href="../../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" type="text/css" href="../../light.css" id="themeStyle"><link rel="stylesheet" type="text/css" href="../../dark.css" disabled ><link rel="stylesheet" type="text/css" href="../../ayu.css" disabled ><script id="default-settings"></script><script src="../../storage.js"></script><noscript><link rel="stylesheet" href="../../noscript.css"></noscript><link rel="icon" type="image/svg+xml" href="../../favicon.svg">
|
||
<link rel="alternate icon" type="image/png" href="../../favicon-16x16.png">
|
||
<link rel="alternate icon" type="image/png" href="../../favicon-32x32.png"><style type="text/css">#crate-search{background-image:url("../../down-arrow.svg");}</style></head><body class="rustdoc fn"><!--[if lte IE 8]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><div class="sidebar-menu">☰</div><a href='../../tokio/index.html'><div class='logo-container rust-logo'><img src='../../rust-logo.png' alt='logo'></div></a><div class="sidebar-elems"><p class="location"><a href="../index.html">tokio</a>::<wbr><a href="index.html">task</a></p><script>window.sidebarCurrent = {name: "spawn", ty: "fn", relpath: ""};</script><script defer src="sidebar-items.js"></script></div></nav><div class="theme-picker"><button id="theme-picker" aria-label="Pick another theme!" aria-haspopup="menu"><img src="../../brush.svg" width="18" alt="Pick another theme!"></button><div id="theme-choices" role="menu"></div></div><script src="../../theme.js"></script><nav class="sub"><form class="search-form"><div class="search-container"><div><select id="crate-search"><option value="All crates">All crates</option></select><input class="search-input" name="search" disabled autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"></div><span class="help-button">?</span>
|
||
<a id="settings-menu" href="../../settings.html"><img src="../../wheel.svg" width="18" alt="Change settings"></a></div></form></nav><section id="main" class="content"><h1 class="fqn"><span class="out-of-band"><span id="render-detail"><a id="toggle-all-docs" href="javascript:void(0)" title="collapse all docs">[<span class="inner">−</span>]</a></span><a class="srclink" href="../../src/tokio/task/spawn.rs.html#126-135" title="goto source code">[src]</a></span><span class="in-band">Function <a href="../index.html">tokio</a>::<wbr><a href="index.html">task</a>::<wbr><a class="fn" href="">spawn</a></span></h1><pre class="rust fn">pub fn spawn<T>(task: T) -> <a class="struct" href="../../tokio/task/struct.JoinHandle.html" title="struct tokio::task::JoinHandle">JoinHandle</a><T::<a class="type" href="https://doc.rust-lang.org/nightly/core/future/future/trait.Future.html#associatedtype.Output" title="type core::future::future::Future::Output">Output</a>><span class="notable-traits"><span class="notable-traits-tooltip">ⓘ<div class="notable-traits-tooltiptext"><span class="docblock"><h3 class="notable">Notable traits for <a class="struct" href="../../tokio/task/struct.JoinHandle.html" title="struct tokio::task::JoinHandle">JoinHandle</a><T></h3><code class="content"><span class="where fmt-newline">impl<T> <a class="trait" href="https://doc.rust-lang.org/nightly/core/future/future/trait.Future.html" title="trait core::future::future::Future">Future</a> for <a class="struct" href="../../tokio/task/struct.JoinHandle.html" title="struct tokio::task::JoinHandle">JoinHandle</a><T></span><span class="where fmt-newline"> type <a href="https://doc.rust-lang.org/nightly/core/future/future/trait.Future.html#associatedtype.Output" class="type">Output</a> = <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a><T, <a class="struct" href="../../tokio/task/struct.JoinError.html" title="struct tokio::task::JoinError">JoinError</a>>;</span></code></span></div></span></span> <span class="where fmt-newline">where<br> T: <a class="trait" href="https://doc.rust-lang.org/nightly/core/future/future/trait.Future.html" title="trait core::future::future::Future">Future</a> + <a class="trait" href="https://doc.rust-lang.org/nightly/core/marker/trait.Send.html" title="trait core::marker::Send">Send</a> + 'static,<br> T::<a class="type" href="https://doc.rust-lang.org/nightly/core/future/future/trait.Future.html#associatedtype.Output" title="type core::future::future::Future::Output">Output</a>: <a class="trait" href="https://doc.rust-lang.org/nightly/core/marker/trait.Send.html" title="trait core::marker::Send">Send</a> + 'static, </span></pre><div class="docblock"><p>Spawns a new asynchronous task, returning a
|
||
<a href="../../tokio/task/struct.JoinHandle.html"><code>JoinHandle</code></a> for it.</p>
|
||
<p>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
|
||
<a href="../../tokio/runtime/struct.Runtime.html"><code>Runtime</code></a> configuration.</p>
|
||
<p>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.</p>
|
||
<p>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 <a href="../../tokio/runtime/struct.Runtime.html#method.enter"><code>Runtime::enter</code></a> method.</p>
|
||
<h1 id="examples" class="section-header"><a href="#examples">Examples</a></h1>
|
||
<p>In this example, a server is started and <code>spawn</code> is used to start a new task
|
||
that processes each received connection.</p>
|
||
|
||
<div class="example-wrap"><pre class="rust rust-example-rendered">
|
||
<span class="kw">use</span> <span class="ident">tokio</span>::<span class="ident">net</span>::{<span class="ident">TcpListener</span>, <span class="ident">TcpStream</span>};
|
||
|
||
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">io</span>;
|
||
|
||
<span class="ident">async</span> <span class="kw">fn</span> <span class="ident">process</span>(<span class="ident">socket</span>: <span class="ident">TcpStream</span>) {
|
||
<span class="comment">// ...</span>
|
||
}
|
||
|
||
<span class="attribute">#[<span class="ident">tokio</span>::<span class="ident">main</span>]</span>
|
||
<span class="ident">async</span> <span class="kw">fn</span> <span class="ident">main</span>() <span class="op">-</span><span class="op">></span> <span class="ident">io</span>::<span class="prelude-ty">Result</span><span class="op"><</span>()<span class="op">></span> {
|
||
<span class="kw">let</span> <span class="ident">listener</span> <span class="op">=</span> <span class="ident">TcpListener</span>::<span class="ident">bind</span>(<span class="string">"127.0.0.1:8080"</span>).<span class="ident">await</span><span class="question-mark">?</span>;
|
||
|
||
<span class="kw">loop</span> {
|
||
<span class="kw">let</span> (<span class="ident">socket</span>, <span class="kw">_</span>) <span class="op">=</span> <span class="ident">listener</span>.<span class="ident">accept</span>().<span class="ident">await</span><span class="question-mark">?</span>;
|
||
|
||
<span class="ident">tokio</span>::<span class="ident">spawn</span>(<span class="ident">async</span> <span class="kw">move</span> {
|
||
<span class="comment">// Process each socket concurrently.</span>
|
||
<span class="ident">process</span>(<span class="ident">socket</span>).<span class="ident">await</span>
|
||
});
|
||
}
|
||
}</pre></div>
|
||
<h1 id="panics" class="section-header"><a href="#panics">Panics</a></h1>
|
||
<p>Panics if called from <strong>outside</strong> of the Tokio runtime.</p>
|
||
<h1 id="using-send-values-from-a-task" class="section-header"><a href="#using-send-values-from-a-task">Using <code>!Send</code> values from a task</a></h1>
|
||
<p>The task supplied to <code>spawn</code> must implement <code>Send</code>. However, it is
|
||
possible to <strong>use</strong> <code>!Send</code> values from the task as long as they only
|
||
exist between calls to <code>.await</code>.</p>
|
||
<p>For example, this will work:</p>
|
||
|
||
<div class="example-wrap"><pre class="rust rust-example-rendered">
|
||
<span class="kw">use</span> <span class="ident">tokio</span>::<span class="ident">task</span>;
|
||
|
||
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">rc</span>::<span class="ident">Rc</span>;
|
||
|
||
<span class="kw">fn</span> <span class="ident">use_rc</span>(<span class="ident">rc</span>: <span class="ident">Rc</span><span class="op"><</span>()<span class="op">></span>) {
|
||
<span class="comment">// Do stuff w/ rc</span>
|
||
}
|
||
|
||
<span class="attribute">#[<span class="ident">tokio</span>::<span class="ident">main</span>]</span>
|
||
<span class="ident">async</span> <span class="kw">fn</span> <span class="ident">main</span>() {
|
||
<span class="ident">tokio</span>::<span class="ident">spawn</span>(<span class="ident">async</span> {
|
||
<span class="comment">// Force the `Rc` to stay in a scope with no `.await`</span>
|
||
{
|
||
<span class="kw">let</span> <span class="ident">rc</span> <span class="op">=</span> <span class="ident">Rc</span>::<span class="ident">new</span>(());
|
||
<span class="ident">use_rc</span>(<span class="ident">rc</span>.<span class="ident">clone</span>());
|
||
}
|
||
|
||
<span class="ident">task</span>::<span class="ident">yield_now</span>().<span class="ident">await</span>;
|
||
}).<span class="ident">await</span>.<span class="ident">unwrap</span>();
|
||
}</pre></div>
|
||
<p>This will <strong>not</strong> work:</p>
|
||
|
||
<div class='information'><div class='tooltip compile_fail'>ⓘ<span class='tooltiptext'>This example deliberately fails to compile</span></div></div><div class="example-wrap"><pre class="rust rust-example-rendered compile_fail">
|
||
<span class="kw">use</span> <span class="ident">tokio</span>::<span class="ident">task</span>;
|
||
|
||
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">rc</span>::<span class="ident">Rc</span>;
|
||
|
||
<span class="kw">fn</span> <span class="ident">use_rc</span>(<span class="ident">rc</span>: <span class="ident">Rc</span><span class="op"><</span>()<span class="op">></span>) {
|
||
<span class="comment">// Do stuff w/ rc</span>
|
||
}
|
||
|
||
<span class="attribute">#[<span class="ident">tokio</span>::<span class="ident">main</span>]</span>
|
||
<span class="ident">async</span> <span class="kw">fn</span> <span class="ident">main</span>() {
|
||
<span class="ident">tokio</span>::<span class="ident">spawn</span>(<span class="ident">async</span> {
|
||
<span class="kw">let</span> <span class="ident">rc</span> <span class="op">=</span> <span class="ident">Rc</span>::<span class="ident">new</span>(());
|
||
|
||
<span class="ident">task</span>::<span class="ident">yield_now</span>().<span class="ident">await</span>;
|
||
|
||
<span class="ident">use_rc</span>(<span class="ident">rc</span>.<span class="ident">clone</span>());
|
||
}).<span class="ident">await</span>.<span class="ident">unwrap</span>();
|
||
}</pre></div>
|
||
<p>Holding on to a <code>!Send</code> value across calls to <code>.await</code> will result in
|
||
an unfriendly compile error message similar to:</p>
|
||
<pre><code class="language-text">`[... some type ...]` cannot be sent between threads safely
|
||
</code></pre>
|
||
<p>or:</p>
|
||
<pre><code class="language-text">error[E0391]: cycle detected when processing `main`
|
||
</code></pre>
|
||
</div></section><section id="search" class="content hidden"></section><section class="footer"></section><script>window.rootPath = "../../";window.currentCrate = "tokio";</script><script src="../../main.js"></script><script defer src="../../search-index.js"></script></body></html> |