| <!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/runtime/handle.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>handle.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::{context, scheduler, RuntimeFlavor}; |
| |
| <span class="doccomment">/// Handle to the runtime. |
| /// |
| /// The handle is internally reference-counted and can be freely cloned. A handle can be |
| /// obtained using the [`Runtime::handle`] method. |
| /// |
| /// [`Runtime::handle`]: crate::runtime::Runtime::handle() |
| </span><span class="attribute">#[derive(Debug, Clone)] |
| </span><span class="comment">// When the `rt` feature is *not* enabled, this type is still defined, but not |
| // included in the public API. |
| </span><span class="kw">pub struct </span>Handle { |
| <span class="kw">pub</span>(<span class="kw">crate</span>) inner: scheduler::Handle, |
| } |
| |
| <span class="kw">use </span><span class="kw">crate</span>::runtime::task::JoinHandle; |
| <span class="kw">use </span><span class="kw">crate</span>::util::error::{CONTEXT_MISSING_ERROR, THREAD_LOCAL_DESTROYED_ERROR}; |
| |
| <span class="kw">use </span>std::future::Future; |
| <span class="kw">use </span>std::marker::PhantomData; |
| <span class="kw">use </span>std::{error, fmt}; |
| |
| <span class="doccomment">/// Runtime context guard. |
| /// |
| /// Returned by [`Runtime::enter`] and [`Handle::enter`], the context guard exits |
| /// the runtime context on drop. |
| /// |
| /// [`Runtime::enter`]: fn@crate::runtime::Runtime::enter |
| </span><span class="attribute">#[derive(Debug)] |
| #[must_use = <span class="string">"Creating and dropping a guard does nothing"</span>] |
| </span><span class="kw">pub struct </span>EnterGuard<<span class="lifetime">'a</span>> { |
| _guard: context::SetCurrentGuard, |
| _handle_lifetime: PhantomData<<span class="kw-2">&</span><span class="lifetime">'a </span>Handle>, |
| } |
| |
| <span class="kw">impl </span>Handle { |
| <span class="doccomment">/// Enters the runtime context. This allows you to construct types that must |
| /// have an executor available on creation such as [`Sleep`] or [`TcpStream`]. |
| /// It will also allow you to call methods such as [`tokio::spawn`] and [`Handle::current`] |
| /// without panicking. |
| /// |
| /// [`Sleep`]: struct@crate::time::Sleep |
| /// [`TcpStream`]: struct@crate::net::TcpStream |
| /// [`tokio::spawn`]: fn@crate::spawn |
| </span><span class="kw">pub fn </span>enter(<span class="kw-2">&</span><span class="self">self</span>) -> EnterGuard<<span class="lifetime">'_</span>> { |
| EnterGuard { |
| _guard: <span class="kw">match </span>context::try_set_current(<span class="kw-2">&</span><span class="self">self</span>.inner) { |
| <span class="prelude-val">Some</span>(guard) => guard, |
| <span class="prelude-val">None </span>=> <span class="macro">panic!</span>(<span class="string">"{}"</span>, <span class="kw">crate</span>::util::error::THREAD_LOCAL_DESTROYED_ERROR), |
| }, |
| _handle_lifetime: PhantomData, |
| } |
| } |
| |
| <span class="doccomment">/// Returns a `Handle` view over the currently running `Runtime`. |
| /// |
| /// # Panics |
| /// |
| /// This will panic if called outside the context of a Tokio runtime. That means that you must |
| /// call this on one of the threads **being run by the runtime**, or from a thread with an active |
| /// `EnterGuard`. Calling this from within a thread created by `std::thread::spawn` (for example) |
| /// will cause a panic unless that thread has an active `EnterGuard`. |
| /// |
| /// # Examples |
| /// |
| /// This can be used to obtain the handle of the surrounding runtime from an async |
| /// block or function running on that runtime. |
| /// |
| /// ``` |
| /// # use std::thread; |
| /// # use tokio::runtime::Runtime; |
| /// # fn dox() { |
| /// # let rt = Runtime::new().unwrap(); |
| /// # rt.spawn(async { |
| /// use tokio::runtime::Handle; |
| /// |
| /// // Inside an async block or function. |
| /// let handle = Handle::current(); |
| /// handle.spawn(async { |
| /// println!("now running in the existing Runtime"); |
| /// }); |
| /// |
| /// # let handle = |
| /// thread::spawn(move || { |
| /// // Notice that the handle is created outside of this thread and then moved in |
| /// handle.spawn(async { /* ... */ }); |
| /// // This next line would cause a panic because we haven't entered the runtime |
| /// // and created an EnterGuard |
| /// // let handle2 = Handle::current(); // panic |
| /// // So we create a guard here with Handle::enter(); |
| /// let _guard = handle.enter(); |
| /// // Now we can call Handle::current(); |
| /// let handle2 = Handle::current(); |
| /// }); |
| /// # handle.join().unwrap(); |
| /// # }); |
| /// # } |
| /// ``` |
| </span><span class="attribute">#[track_caller] |
| </span><span class="kw">pub fn </span>current() -> <span class="self">Self </span>{ |
| Handle { |
| inner: scheduler::Handle::current(), |
| } |
| } |
| |
| <span class="doccomment">/// Returns a Handle view over the currently running Runtime |
| /// |
| /// Returns an error if no Runtime has been started |
| /// |
| /// Contrary to `current`, this never panics |
| </span><span class="kw">pub fn </span>try_current() -> <span class="prelude-ty">Result</span><<span class="self">Self</span>, TryCurrentError> { |
| context::try_current().map(|inner| Handle { inner }) |
| } |
| |
| <span class="doccomment">/// Spawns 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. |
| /// |
| /// 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. |
| /// |
| /// 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(); |
| /// // Get a handle from this runtime |
| /// let handle = rt.handle(); |
| /// |
| /// // Spawn a future onto the runtime using the handle |
| /// handle.spawn(async { |
| /// println!("now running on a worker thread"); |
| /// }); |
| /// # } |
| /// ``` |
| </span><span class="attribute">#[track_caller] |
| </span><span class="kw">pub fn </span>spawn<F>(<span class="kw-2">&</span><span class="self">self</span>, future: F) -> JoinHandle<F::Output> |
| <span class="kw">where |
| </span>F: Future + Send + <span class="lifetime">'static</span>, |
| F::Output: Send + <span class="lifetime">'static</span>, |
| { |
| <span class="self">self</span>.spawn_named(future, <span class="prelude-val">None</span>) |
| } |
| |
| <span class="doccomment">/// Runs the provided function on an executor dedicated to blocking. |
| /// operations. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use tokio::runtime::Runtime; |
| /// |
| /// # fn dox() { |
| /// // Create the runtime |
| /// let rt = Runtime::new().unwrap(); |
| /// // Get a handle from this runtime |
| /// let handle = rt.handle(); |
| /// |
| /// // Spawn a blocking function onto the runtime using the handle |
| /// handle.spawn_blocking(|| { |
| /// println!("now running on a worker thread"); |
| /// }); |
| /// # } |
| </span><span class="attribute">#[track_caller] |
| </span><span class="kw">pub fn </span>spawn_blocking<F, R>(<span class="kw-2">&</span><span class="self">self</span>, func: F) -> JoinHandle<R> |
| <span class="kw">where |
| </span>F: FnOnce() -> R + Send + <span class="lifetime">'static</span>, |
| R: Send + <span class="lifetime">'static</span>, |
| { |
| <span class="self">self</span>.inner.blocking_spawner().spawn_blocking(<span class="self">self</span>, func) |
| } |
| |
| <span class="doccomment">/// Runs a future to completion on this `Handle`'s associated `Runtime`. |
| /// |
| /// This runs the given future on the current thread, 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. |
| /// |
| /// When this is used on a `current_thread` runtime, only the |
| /// [`Runtime::block_on`] method can drive the IO and timer drivers, but the |
| /// `Handle::block_on` method cannot drive them. This means that, when using |
| /// this method on a current_thread runtime, anything that relies on IO or |
| /// timers will not work unless there is another thread currently calling |
| /// [`Runtime::block_on`] on the same runtime. |
| /// |
| /// # If the runtime has been shut down |
| /// |
| /// If the `Handle`'s associated `Runtime` has been shut down (through |
| /// [`Runtime::shutdown_background`], [`Runtime::shutdown_timeout`], or by |
| /// dropping it) and `Handle::block_on` is used it might return an error or |
| /// panic. Specifically IO resources will return an error and timers will |
| /// panic. Runtime independent futures will run as normal. |
| /// |
| /// # Panics |
| /// |
| /// This function panics if the provided future panics, if called within an |
| /// asynchronous execution context, or if a timer future is executed on a |
| /// runtime that has been shut down. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use tokio::runtime::Runtime; |
| /// |
| /// // Create the runtime |
| /// let rt = Runtime::new().unwrap(); |
| /// |
| /// // Get a handle from this runtime |
| /// let handle = rt.handle(); |
| /// |
| /// // Execute the future, blocking the current thread until completion |
| /// handle.block_on(async { |
| /// println!("hello"); |
| /// }); |
| /// ``` |
| /// |
| /// Or using `Handle::current`: |
| /// |
| /// ``` |
| /// use tokio::runtime::Handle; |
| /// |
| /// #[tokio::main] |
| /// async fn main () { |
| /// let handle = Handle::current(); |
| /// std::thread::spawn(move || { |
| /// // Using Handle::block_on to run async code in the new thread. |
| /// handle.block_on(async { |
| /// println!("hello"); |
| /// }); |
| /// }); |
| /// } |
| /// ``` |
| /// |
| /// [`JoinError`]: struct@crate::task::JoinError |
| /// [`JoinHandle`]: struct@crate::task::JoinHandle |
| /// [`Runtime::block_on`]: fn@crate::runtime::Runtime::block_on |
| /// [`Runtime::shutdown_background`]: fn@crate::runtime::Runtime::shutdown_background |
| /// [`Runtime::shutdown_timeout`]: fn@crate::runtime::Runtime::shutdown_timeout |
| /// [`spawn_blocking`]: crate::task::spawn_blocking |
| /// [`tokio::fs`]: crate::fs |
| /// [`tokio::net`]: crate::net |
| /// [`tokio::time`]: crate::time |
| </span><span class="attribute">#[track_caller] |
| </span><span class="kw">pub fn </span>block_on<F: Future>(<span class="kw-2">&</span><span class="self">self</span>, future: F) -> F::Output { |
| <span class="attribute">#[cfg(all(tokio_unstable, feature = <span class="string">"tracing"</span>))] |
| </span><span class="kw">let </span>future = |
| <span class="kw">crate</span>::util::trace::task(future, <span class="string">"block_on"</span>, <span class="prelude-val">None</span>, <span class="kw">super</span>::task::Id::next().as_u64()); |
| |
| <span class="comment">// Enter the runtime context. This sets the current driver handles and |
| // prevents blocking an existing runtime. |
| </span><span class="kw">let </span><span class="kw-2">mut </span>enter = context::enter_runtime(<span class="kw-2">&</span><span class="self">self</span>.inner, <span class="bool-val">true</span>); |
| |
| <span class="comment">// Block on the future |
| </span>enter |
| .blocking |
| .block_on(future) |
| .expect(<span class="string">"failed to park thread"</span>) |
| } |
| |
| <span class="attribute">#[track_caller] |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>spawn_named<F>(<span class="kw-2">&</span><span class="self">self</span>, future: F, _name: <span class="prelude-ty">Option</span><<span class="kw-2">&</span>str>) -> JoinHandle<F::Output> |
| <span class="kw">where |
| </span>F: Future + Send + <span class="lifetime">'static</span>, |
| F::Output: Send + <span class="lifetime">'static</span>, |
| { |
| <span class="kw">let </span>id = <span class="kw">crate</span>::runtime::task::Id::next(); |
| <span class="attribute">#[cfg(all(tokio_unstable, feature = <span class="string">"tracing"</span>))] |
| </span><span class="kw">let </span>future = <span class="kw">crate</span>::util::trace::task(future, <span class="string">"task"</span>, _name, id.as_u64()); |
| <span class="self">self</span>.inner.spawn(future, id) |
| } |
| |
| <span class="doccomment">/// Returns the flavor of the current `Runtime`. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use tokio::runtime::{Handle, RuntimeFlavor}; |
| /// |
| /// #[tokio::main(flavor = "current_thread")] |
| /// async fn main() { |
| /// assert_eq!(RuntimeFlavor::CurrentThread, Handle::current().runtime_flavor()); |
| /// } |
| /// ``` |
| /// |
| /// ``` |
| /// use tokio::runtime::{Handle, RuntimeFlavor}; |
| /// |
| /// #[tokio::main(flavor = "multi_thread", worker_threads = 4)] |
| /// async fn main() { |
| /// assert_eq!(RuntimeFlavor::MultiThread, Handle::current().runtime_flavor()); |
| /// } |
| /// ``` |
| </span><span class="kw">pub fn </span>runtime_flavor(<span class="kw-2">&</span><span class="self">self</span>) -> RuntimeFlavor { |
| <span class="kw">match </span><span class="self">self</span>.inner { |
| scheduler::Handle::CurrentThread(<span class="kw">_</span>) => RuntimeFlavor::CurrentThread, |
| <span class="attribute">#[cfg(all(feature = <span class="string">"rt-multi-thread"</span>, not(tokio_wasi)))] |
| </span>scheduler::Handle::MultiThread(<span class="kw">_</span>) => RuntimeFlavor::MultiThread, |
| } |
| } |
| } |
| |
| <span class="macro">cfg_metrics! </span>{ |
| <span class="kw">use </span><span class="kw">crate</span>::runtime::RuntimeMetrics; |
| |
| <span class="kw">impl </span>Handle { |
| <span class="doccomment">/// Returns a view that lets you get information about how the runtime |
| /// is performing. |
| </span><span class="kw">pub fn </span>metrics(<span class="kw-2">&</span><span class="self">self</span>) -> RuntimeMetrics { |
| RuntimeMetrics::new(<span class="self">self</span>.clone()) |
| } |
| } |
| } |
| |
| <span class="doccomment">/// Error returned by `try_current` when no Runtime has been started |
| </span><span class="attribute">#[derive(Debug)] |
| </span><span class="kw">pub struct </span>TryCurrentError { |
| kind: TryCurrentErrorKind, |
| } |
| |
| <span class="kw">impl </span>TryCurrentError { |
| <span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>new_no_context() -> <span class="self">Self </span>{ |
| <span class="self">Self </span>{ |
| kind: TryCurrentErrorKind::NoContext, |
| } |
| } |
| |
| <span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>new_thread_local_destroyed() -> <span class="self">Self </span>{ |
| <span class="self">Self </span>{ |
| kind: TryCurrentErrorKind::ThreadLocalDestroyed, |
| } |
| } |
| |
| <span class="doccomment">/// Returns true if the call failed because there is currently no runtime in |
| /// the Tokio context. |
| </span><span class="kw">pub fn </span>is_missing_context(<span class="kw-2">&</span><span class="self">self</span>) -> bool { |
| <span class="macro">matches!</span>(<span class="self">self</span>.kind, TryCurrentErrorKind::NoContext) |
| } |
| |
| <span class="doccomment">/// Returns true if the call failed because the Tokio context thread-local |
| /// had been destroyed. This can usually only happen if in the destructor of |
| /// other thread-locals. |
| </span><span class="kw">pub fn </span>is_thread_local_destroyed(<span class="kw-2">&</span><span class="self">self</span>) -> bool { |
| <span class="macro">matches!</span>(<span class="self">self</span>.kind, TryCurrentErrorKind::ThreadLocalDestroyed) |
| } |
| } |
| |
| <span class="kw">enum </span>TryCurrentErrorKind { |
| NoContext, |
| ThreadLocalDestroyed, |
| } |
| |
| <span class="kw">impl </span>fmt::Debug <span class="kw">for </span>TryCurrentErrorKind { |
| <span class="kw">fn </span>fmt(<span class="kw-2">&</span><span class="self">self</span>, f: <span class="kw-2">&mut </span>fmt::Formatter<<span class="lifetime">'_</span>>) -> fmt::Result { |
| <span class="kw">use </span>TryCurrentErrorKind::<span class="kw-2">*</span>; |
| <span class="kw">match </span><span class="self">self </span>{ |
| NoContext => f.write_str(<span class="string">"NoContext"</span>), |
| ThreadLocalDestroyed => f.write_str(<span class="string">"ThreadLocalDestroyed"</span>), |
| } |
| } |
| } |
| |
| <span class="kw">impl </span>fmt::Display <span class="kw">for </span>TryCurrentError { |
| <span class="kw">fn </span>fmt(<span class="kw-2">&</span><span class="self">self</span>, f: <span class="kw-2">&mut </span>fmt::Formatter<<span class="lifetime">'_</span>>) -> fmt::Result { |
| <span class="kw">use </span>TryCurrentErrorKind::<span class="kw-2">*</span>; |
| <span class="kw">match </span><span class="self">self</span>.kind { |
| NoContext => f.write_str(CONTEXT_MISSING_ERROR), |
| ThreadLocalDestroyed => f.write_str(THREAD_LOCAL_DESTROYED_ERROR), |
| } |
| } |
| } |
| |
| <span class="kw">impl </span>error::Error <span class="kw">for </span>TryCurrentError {} |
| </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> |
