<!DOCTYPE html><htmllang="en"><head><metacharset="utf-8"><metaname="viewport"content="width=device-width, initial-scale=1.0"><metaname="generator"content="rustdoc"><metaname="description"content="Storage for span data shared by multiple `Layer`s."><title>tracing_subscriber::registry - Rust</title><linkrel="preload"as="font"type="font/woff2"crossoriginhref="../../static.files/SourceSerif4-Regular-46f98efaafac5295.ttf.woff2"><linkrel="preload"as="font"type="font/woff2"crossoriginhref="../../static.files/FiraSans-Regular-018c141bf0843ffd.woff2"><linkrel="preload"as="font"type="font/woff2"crossoriginhref="../../static.files/FiraSans-Medium-8f9a781e4970d388.woff2"><linkrel="preload"as="font"type="font/woff2"crossoriginhref="../../static.files/SourceCodePro-Regular-562dcc5011b6de7d.ttf.woff2"><linkrel="preload"as="font"type="font/woff2"crossoriginhref="../../static.files/SourceCodePro-Semibold-d899c5a5c4aeb14a.ttf.woff2"><linkrel="stylesheet"href="../../static.files/normalize-76eba96aa4d2e634.css"><linkrel="stylesheet"href="../../static.files/rustdoc-5bc39a1768837dd0.css"><metaname="rustdoc-vars"data-root-path="../../"data-static-root-path="../../static.files/"data-current-crate="tracing_subscriber"data-themes=""data-resource-suffix=""data-rustdoc-version="1.77.0 (aedd173a2 2024-03-17)"data-channel="1.77.0"data-search-js="search-dd67cee4cfa65049.js"data-settings-js="settings-4313503d2e1961c2.js"><scriptsrc="../../static.files/storage-4c98445ec4002617.js"></script><scriptdefersrc="../sidebar-items.js"></script><scriptdefersrc="../../static.files/main-48f368f3872407c8.js"></script><noscript><linkrel="stylesheet"href="../../static.files/noscript-04d5337699b92874.css"></noscript><linkrel="alternate icon"type="image/png"href="../../static.files/favicon-16x16-8b506e7a72182f1c.png"><linkrel="alternate icon"type="image/png"href="../../static.files/favicon-32x32-422f7d1d52889060.png"><linkrel="icon"type="image/svg+xml"href="../../static.files/favicon-2c020d218678b618.svg"></head><bodyclass="rustdoc mod"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><navclass="mobile-topbar"><buttonclass="sidebar-menu-toggle"title="show sidebar"></button><aclass="logo-container"href="../../tracing_subscriber/index.html"><imgsrc="https://raw.githubusercontent.com/tokio-rs/tracing/master/assets/logo-type.png"alt=""></a></nav><navclass="sidebar"><divclass="sidebar-crate"><aclass="logo-container"href="../../tracing_subscriber/index.html"><imgsrc="https://raw.githubusercontent.com/tokio-rs/tracing/master/assets/logo-type.png"alt="logo"></a><h2><ahref="../../tracing_subscriber/index.html">tracing_subscriber</a><spanclass="version">0.3.18</span></h2></div><h2class="location"><ahref="#">Module registry</a></h2><divclass="sidebar-elems"><section><ulclass="block"><li><ahref="#structs">Structs</a></li><li><ahref="#traits">Traits</a></li></ul></section><h2><ahref="../index.html">In crate tracing_subscriber</a></h2></div></nav><divclass="sidebar-resizer"></div>
<main><divclass="width-limiter"><navclass="sub"><formclass="search-form"><span></span><divid="sidebar-button"tabindex="-1"><ahref="../../tracing_subscriber/all.html"title="show sidebar"></a></div><inputclass="search-input"name="search"aria-label="Run search in the documentation"autocomplete="off"spellcheck="false"placeholder="Click or press ‘S’ to search, ‘?’ for more options…"type="search"><divid="help-button"tabindex="-1"><ahref="../../help.html"title="help">?</a></div><divid="settings-menu"tabindex="-1"><ahref="../../settings.html"title="settings"><imgwidth="22"height="22"alt="Change settings"src="../../static.files/wheel-7b819b6101059cd0.svg"></a></div></form></nav><sectionid="main-content"class="content"><divclass="main-heading"><h1>Module <ahref="../index.html">tracing_subscriber</a>::<wbr><aclass="mod"href="#">registry</a><buttonid="copy-path"title="Copy item path to clipboard"><imgsrc="../../static.files/clipboard-7571035ce49a181d.svg"width="19"height="18"alt="Copy item path"></button></h1><spanclass="out-of-band"><aclass="src"href="../../src/tracing_subscriber/registry/mod.rs.html#1-598">source</a> · <buttonid="toggle-all-docs"title="collapse all docs">[<span>−</span>]</button></span></div><detailsclass="toggle top-doc"open><summaryclass="hideme"><span>Expand description</span></summary><divclass="docblock"><p>Storage for span data shared by multiple <ahref="../layer/trait.Layer.html"title="trait tracing_subscriber::layer::Layer"><code>Layer</code></a>s.</p>
<p>This module provides the <ahref="struct.Registry.html"title="struct tracing_subscriber::registry::Registry"><code>Registry</code></a> type, a <ahref="../../tracing_core/subscriber/trait.Subscriber.html"title="trait tracing_core::subscriber::Subscriber"><code>Subscriber</code></a> implementation
which tracks per-span data and exposes it to <ahref="../layer/trait.Layer.html"title="trait tracing_subscriber::layer::Layer"><code>Layer</code></a>s. When a <code>Registry</code>
is used as the base <code>Subscriber</code> of a <code>Layer</code> stack, the
<ahref="../layer/struct.Context.html"title="struct tracing_subscriber::layer::Context"><code>layer::Context</code></a> type will provide methods allowing <code>Layer</code>s to
<ahref="../layer/struct.Context.html#method.span"title="method tracing_subscriber::layer::Context::span">look up span data</a> stored in the registry. While <ahref="struct.Registry.html"title="struct tracing_subscriber::registry::Registry"><code>Registry</code></a> is a
reasonable default for storing spans and events, other stores that implement
<ahref="trait.LookupSpan.html"title="trait tracing_subscriber::registry::LookupSpan"><code>LookupSpan</code></a> and <ahref="../../tracing_core/subscriber/trait.Subscriber.html"title="trait tracing_core::subscriber::Subscriber"><code>Subscriber</code></a> themselves (with <ahref="trait.SpanData.html"title="trait tracing_subscriber::registry::SpanData"><code>SpanData</code></a> implemented
by the per-span data they store) can be used as a drop-in replacement.</p>
<p>For example, we might create a <code>Registry</code> and add multiple <code>Layer</code>s like so:</p>
<p>When this bound is added, the <code>Layer</code> implementation will be guaranteed
access to the <ahref="../layer/struct.Context.html"title="struct tracing_subscriber::layer::Context"><code>Context</code></a> methods, such as <ahref="../layer/struct.Context.html#method.span"title="method tracing_subscriber::layer::Context::span"><code>Context::span</code></a>, that
</div></details><h2id="structs"class="section-header">Structs<ahref="#structs"class="anchor">§</a></h2><ulclass="item-table"><li><divclass="item-name"><aclass="struct"href="struct.Data.html"title="struct tracing_subscriber::registry::Data">Data</a></div><divclass="desc docblock-short">Span data stored in a <ahref="struct.Registry.html"title="struct tracing_subscriber::registry::Registry"><code>Registry</code></a>.</div></li><li><divclass="item-name"><aclass="struct"href="struct.Extensions.html"title="struct tracing_subscriber::registry::Extensions">Extensions</a></div><divclass="desc docblock-short">An immutable, read-only reference to a Span’s extensions.</div></li><li><divclass="item-name"><aclass="struct"href="struct.ExtensionsMut.html"title="struct tracing_subscriber::registry::ExtensionsMut">ExtensionsMut</a></div><divclass="desc docblock-short">An mutable reference to a Span’s extensions.</div></li><li><divclass="item-name"><aclass="struct"href="struct.Registry.html"title="struct tracing_subscriber::registry::Registry">Registry</a></div><divclass="desc docblock-short">A shared, reusable store for spans.</div></li><li><divclass="item-name"><aclass="struct"href="struct.Scope.html"title="struct tracing_subscriber::registry::Scope">Scope</a></div><divclass="desc docblock-short">An iterator over the parents of a span, ordered from leaf to root.</div></li><li><divclass="item-name"><aclass="struct"href="struct.ScopeFromRoot.html"title="struct tracing_subscriber::registry::ScopeFromRoot">ScopeFromRoot</a></div><divclass="desc docblock-short">An iterator over the parents of a span, ordered from root to leaf.</div></li><li><divclass="item-name"><aclass="struct"href="struct.SpanRef.html"title="struct tracing_subscriber::registry::SpanRef">SpanRef</a></div><divclass="desc docblock-short">A reference to [span data] and the associated <ahref="trait.LookupSpan.html"title="trait tracing_subscriber::registry::LookupSpan">registry</a>.</div></li></ul><h2id="traits"class="section-header">Traits<ahref="#traits"class="anchor">§</a></h2><ulclass="item-table"><li><divclass="item-name"><aclass="trait"href="trait.LookupSpan.html"title="trait tracing_subscriber::registry::LookupSpan">LookupSpan</a></div><divclass="desc docblock-short">Provides access to stored span data.</div></li><li><divclass="item-name"><aclass="trait"href="trait.SpanData.html"title="trait tracing_subscriber::registry::SpanData">SpanData</a></div><divclass="desc docblock-short">A stored representation of data associated with a span.</div></li></ul></section></div></main></body></html>