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<!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="Extension trait allowing futures to be instrumented with a `tracing` `Subscriber`."><title>WithSubscriber in tracing::instrument - Rust</title><script>if(window.location.protocol!=="file:")document.head.insertAdjacentHTML("beforeend","SourceSerif4-Regular-6b053e98.ttf.woff2,FiraSans-Italic-81dc35de.woff2,FiraSans-Regular-0fe48ade.woff2,FiraSans-MediumItalic-ccf7e434.woff2,FiraSans-Medium-e1aa3f0a.woff2,SourceCodePro-Regular-8badfe75.ttf.woff2,SourceCodePro-Semibold-aa29a496.ttf.woff2".split(",").map(f=>`<link rel="preload" as="font" type="font/woff2"href="../../static.files/${f}">`).join(""))</script><link rel="stylesheet" href="../../static.files/normalize-9960930a.css"><link rel="stylesheet" href="../../static.files/rustdoc-ca0dd0c4.css"><meta name="rustdoc-vars" data-root-path="../../" data-static-root-path="../../static.files/" data-current-crate="tracing" data-themes="" data-resource-suffix="" data-rustdoc-version="1.93.1 (01f6ddf75 2026-02-11) (Arch Linux rust 1:1.93.1-1)" data-channel="1.93.1" data-search-js="search-9e2438ea.js" data-stringdex-js="stringdex-a3946164.js" data-settings-js="settings-c38705f0.js" ><script src="../../static.files/storage-e2aeef58.js"></script><script defer src="sidebar-items.js"></script><script defer src="../../static.files/main-a410ff4d.js"></script><noscript><link rel="stylesheet" href="../../static.files/noscript-263c88ec.css"></noscript><link rel="icon" href="https://raw.githubusercontent.com/tokio-rs/tracing/main/assets/favicon.ico"></head><body class="rustdoc trait"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><rustdoc-topbar><h2><a href="#">WithSubscriber</a></h2></rustdoc-topbar><nav class="sidebar"><div class="sidebar-crate"><a class="logo-container" href="../../tracing/index.html"><img src="https://raw.githubusercontent.com/tokio-rs/tracing/main/assets/logo-type.png" alt="logo"></a><h2><a href="../../tracing/index.html">tracing</a><span class="version">0.1.44</span></h2></div><div class="sidebar-elems"><section id="rustdoc-toc"><h2 class="location"><a href="#">With<wbr>Subscriber</a></h2><h3><a href="#provided-methods">Provided Methods</a></h3><ul class="block"><li><a href="#method.with_current_subscriber" title="with_current_subscriber">with_current_subscriber</a></li><li><a href="#method.with_subscriber" title="with_subscriber">with_subscriber</a></li></ul><h3><a href="#dyn-compatibility">Dyn Compatibility</a></h3><h3><a href="#implementors">Implementors</a></h3></section><div id="rustdoc-modnav"><h2><a href="index.html">In tracing::<wbr>instrument</a></h2></div></div></nav><div class="sidebar-resizer" title="Drag to resize sidebar"></div><main><div class="width-limiter"><section id="main-content" class="content"><div class="main-heading"><div class="rustdoc-breadcrumbs"><a href="../index.html">tracing</a>::<wbr><a href="index.html">instrument</a></div><h1>Trait <span class="trait">With<wbr>Subscriber</span> <button id="copy-path" title="Copy item path to clipboard">Copy item path</button></h1><rustdoc-toolbar></rustdoc-toolbar><span class="sub-heading"><a class="src" href="../../src/tracing/instrument.rs.html#136-234">Source</a> </span></div><pre class="rust item-decl"><code>pub trait WithSubscriber: <a class="trait" href="https://doc.rust-lang.org/1.93.1/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a> {
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// Provided methods
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fn <a href="#method.with_subscriber" class="fn">with_subscriber</a><S>(self, subscriber: S) -> <a class="struct" href="struct.WithDispatch.html" title="struct tracing::instrument::WithDispatch">WithDispatch</a><Self> <a href="#" class="tooltip" data-notable-ty="WithDispatch<Self>">ⓘ</a>
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<span class="where">where S: <a class="trait" href="https://doc.rust-lang.org/1.93.1/core/convert/trait.Into.html" title="trait core::convert::Into">Into</a><<a class="struct" href="../struct.Dispatch.html" title="struct tracing::Dispatch">Dispatch</a>></span> { ... }
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<span class="item-spacer"></span> fn <a href="#method.with_current_subscriber" class="fn">with_current_subscriber</a>(self) -> <a class="struct" href="struct.WithDispatch.html" title="struct tracing::instrument::WithDispatch">WithDispatch</a><Self> <a href="#" class="tooltip" data-notable-ty="WithDispatch<Self>">ⓘ</a> { ... }
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}</code></pre><details class="toggle top-doc" open><summary class="hideme"><span>Expand description</span></summary><div class="docblock"><p>Extension trait allowing futures to be instrumented with
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a <code>tracing</code> <a href="../trait.Subscriber.html" title="trait tracing::Subscriber"><code>Subscriber</code></a>.</p>
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</div></details><h2 id="provided-methods" class="section-header">Provided Methods<a href="#provided-methods" class="anchor">§</a></h2><div class="methods"><details class="toggle method-toggle" open><summary><section id="method.with_subscriber" class="method"><a class="src rightside" href="../../src/tracing/instrument.rs.html#176-184">Source</a><h4 class="code-header">fn <a href="#method.with_subscriber" class="fn">with_subscriber</a><S>(self, subscriber: S) -> <a class="struct" href="struct.WithDispatch.html" title="struct tracing::instrument::WithDispatch">WithDispatch</a><Self> <a href="#" class="tooltip" data-notable-ty="WithDispatch<Self>">ⓘ</a><div class="where">where
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S: <a class="trait" href="https://doc.rust-lang.org/1.93.1/core/convert/trait.Into.html" title="trait core::convert::Into">Into</a><<a class="struct" href="../struct.Dispatch.html" title="struct tracing::Dispatch">Dispatch</a>>,</div></h4></section></summary><div class="docblock"><p>Attaches the provided <a href="../trait.Subscriber.html" title="trait tracing::Subscriber"><code>Subscriber</code></a> to this type, returning a
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<a href="struct.WithDispatch.html" title="struct tracing::instrument::WithDispatch"><code>WithDispatch</code></a> wrapper.</p>
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<p>The attached <a href="../trait.Subscriber.html" title="trait tracing::Subscriber"><code>Subscriber</code></a> will be set as the <a href="../dispatcher/index.html#setting-the-default-subscriber" title="mod tracing::dispatcher">default</a> when the returned
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<a href="https://doc.rust-lang.org/1.93.1/core/future/future/trait.Future.html" title="trait core::future::future::Future"><code>Future</code></a> is polled.</p>
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<h5 id="examples"><a class="doc-anchor" href="#examples">§</a>Examples</h5>
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use </span>tracing::instrument::WithSubscriber;
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<span class="comment">// Set the default `Subscriber`
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</span><span class="kw">let </span>_default = tracing::subscriber::set_default(MySubscriber::default());
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<span class="macro">tracing::info!</span>(<span class="string">"this event will be recorded by the default `Subscriber`"</span>);
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<span class="comment">// Create a different `Subscriber` and attach it to a future.
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</span><span class="kw">let </span>other_subscriber = MyOtherSubscriber::default();
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<span class="kw">let </span>future = <span class="kw">async </span>{
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<span class="macro">tracing::info!</span>(<span class="string">"this event will be recorded by the other `Subscriber`"</span>);
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<span class="comment">// ...
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</span>};
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future
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<span class="comment">// Attach the other `Subscriber` to the future before awaiting it
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</span>.with_subscriber(other_subscriber)
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.<span class="kw">await</span>;
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<span class="comment">// Once the future has completed, we return to the default `Subscriber`.
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</span><span class="macro">tracing::info!</span>(<span class="string">"this event will be recorded by the default `Subscriber`"</span>);</code></pre></div></div></details><details class="toggle method-toggle" open><summary><section id="method.with_current_subscriber" class="method"><a class="src rightside" href="../../src/tracing/instrument.rs.html#228-233">Source</a><h4 class="code-header">fn <a href="#method.with_current_subscriber" class="fn">with_current_subscriber</a>(self) -> <a class="struct" href="struct.WithDispatch.html" title="struct tracing::instrument::WithDispatch">WithDispatch</a><Self> <a href="#" class="tooltip" data-notable-ty="WithDispatch<Self>">ⓘ</a></h4></section></summary><div class="docblock"><p>Attaches the current <a href="../dispatcher/index.html#setting-the-default-subscriber" title="mod tracing::dispatcher">default</a> <a href="../trait.Subscriber.html" title="trait tracing::Subscriber"><code>Subscriber</code></a> to this type, returning a
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<a href="struct.WithDispatch.html" title="struct tracing::instrument::WithDispatch"><code>WithDispatch</code></a> wrapper.</p>
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<p>The attached <code>Subscriber</code> will be set as the <a href="../dispatcher/index.html#setting-the-default-subscriber" title="mod tracing::dispatcher">default</a> when the returned
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<a href="https://doc.rust-lang.org/1.93.1/core/future/future/trait.Future.html" title="trait core::future::future::Future"><code>Future</code></a> is polled.</p>
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<p>This can be used to propagate the current dispatcher context when
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spawning a new future that may run on a different thread.</p>
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<h5 id="examples-1"><a class="doc-anchor" href="#examples-1">§</a>Examples</h5>
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use </span>tracing::instrument::WithSubscriber;
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<span class="comment">// Using `set_default` (rather than `set_global_default`) sets the
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// default `Subscriber` for *this* thread only.
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</span><span class="kw">let </span>_default = tracing::subscriber::set_default(MySubscriber::default());
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<span class="kw">let </span>future = <span class="kw">async </span>{
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<span class="comment">// ...
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</span>};
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<span class="comment">// If a multi-threaded async runtime is in use, this spawned task may
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// run on a different thread, in a different default `Subscriber`'s context.
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</span>tokio::spawn(future);
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<span class="comment">// However, calling `with_current_subscriber` on the future before
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// spawning it, ensures that the current thread's default `Subscriber` is
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// propagated to the spawned task, regardless of where it executes:
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</span>tokio::spawn(future.with_current_subscriber());</code></pre></div></div></details></div><h2 id="dyn-compatibility" class="section-header">Dyn Compatibility<a href="#dyn-compatibility" class="anchor">§</a></h2><div class="dyn-compatibility-info"><p>This trait is <b>not</b> <a href="https://doc.rust-lang.org/1.93.1/reference/items/traits.html#dyn-compatibility">dyn compatible</a>.</p><p><i>In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.</i></p></div><h2 id="implementors" class="section-header">Implementors<a href="#implementors" class="anchor">§</a></h2><div id="implementors-list"><section id="impl-WithSubscriber-for-T" class="impl"><a class="src rightside" href="../../src/tracing/instrument.rs.html#393">Source</a><a href="#impl-WithSubscriber-for-T" class="anchor">§</a><h3 class="code-header">impl<T: <a class="trait" href="https://doc.rust-lang.org/1.93.1/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>> <a class="trait" href="trait.WithSubscriber.html" title="trait tracing::instrument::WithSubscriber">WithSubscriber</a> for T</h3></section></div><script src="../../trait.impl/tracing/instrument/trait.WithSubscriber.js" async></script><script type="text/json" id="notable-traits-data">{"WithDispatch<Self>":"<h3>Notable traits for <code><a class=\"struct\" href=\"struct.WithDispatch.html\" title=\"struct tracing::instrument::WithDispatch\">WithDispatch</a><T></code></h3><pre><code><div class=\"where\">impl<T: <a class=\"trait\" href=\"https://doc.rust-lang.org/1.93.1/core/future/future/trait.Future.html\" title=\"trait core::future::future::Future\">Future</a>> <a class=\"trait\" href=\"https://doc.rust-lang.org/1.93.1/core/future/future/trait.Future.html\" title=\"trait core::future::future::Future\">Future</a> for <a class=\"struct\" href=\"struct.WithDispatch.html\" title=\"struct tracing::instrument::WithDispatch\">WithDispatch</a><T></div><div class=\"where\"> type <a href=\"https://doc.rust-lang.org/1.93.1/core/future/future/trait.Future.html#associatedtype.Output\" class=\"associatedtype\">Output</a> = T::<a class=\"associatedtype\" href=\"https://doc.rust-lang.org/1.93.1/core/future/future/trait.Future.html#associatedtype.Output\" title=\"type core::future::future::Future::Output\">Output</a>;</div>"}</script></section></div></main></body></html> |