edg-l/edlang
1
1
Fork 0
mirror of https://github.com/edg-l/edlang.git synced 2024-11-24 08:58:26 +00:00
Code Issues Packages Projects Releases Wiki Activity
edlang/tracing_core/callsite/index.html
edg-l 99e2ddd36f deploy: 39fc7f2b9f
2024-03-27 11:12:16 +00:00

72 lines
15 KiB
HTML
Raw Blame History

This file contains ambiguous Unicode characters

This file contains Unicode characters that might be confused with other characters. If you think that this is intentional, you can safely ignore this warning. Use the Escape button to reveal them.

<!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="Callsites represent the source locations from which spans or events originate."><title>tracing_core::callsite - Rust</title><link rel="preload" as="font" type="font/woff2" crossorigin href="../../static.files/SourceSerif4-Regular-46f98efaafac5295.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../static.files/FiraSans-Regular-018c141bf0843ffd.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../static.files/FiraSans-Medium-8f9a781e4970d388.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../static.files/SourceCodePro-Regular-562dcc5011b6de7d.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../static.files/SourceCodePro-Semibold-d899c5a5c4aeb14a.ttf.woff2"><link rel="stylesheet" href="../../static.files/normalize-76eba96aa4d2e634.css"><link rel="stylesheet" href="../../static.files/rustdoc-5bc39a1768837dd0.css"><meta name="rustdoc-vars" data-root-path="../../" data-static-root-path="../../static.files/" data-current-crate="tracing_core" 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" ><script src="../../static.files/storage-4c98445ec4002617.js"></script><script defer src="../sidebar-items.js"></script><script defer src="../../static.files/main-48f368f3872407c8.js"></script><noscript><link rel="stylesheet" href="../../static.files/noscript-04d5337699b92874.css"></noscript><link rel="alternate icon" type="image/png" href="../../static.files/favicon-16x16-8b506e7a72182f1c.png"><link rel="alternate icon" type="image/png" href="../../static.files/favicon-32x32-422f7d1d52889060.png"><link rel="icon" type="image/svg+xml" href="../../static.files/favicon-2c020d218678b618.svg"></head><body class="rustdoc mod"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="mobile-topbar"><button class="sidebar-menu-toggle" title="show sidebar"></button><a class="logo-container" href="../../tracing_core/index.html"><img src="https://raw.githubusercontent.com/tokio-rs/tracing/master/assets/logo-type.png" alt=""></a></nav><nav class="sidebar"><div class="sidebar-crate"><a class="logo-container" href="../../tracing_core/index.html"><img src="https://raw.githubusercontent.com/tokio-rs/tracing/master/assets/logo-type.png" alt="logo"></a><h2><a href="../../tracing_core/index.html">tracing_core</a><span class="version">0.1.32</span></h2></div><h2 class="location"><a href="#">Module callsite</a></h2><div class="sidebar-elems"><section><ul class="block"><li><a href="#structs">Structs</a></li><li><a href="#traits">Traits</a></li><li><a href="#functions">Functions</a></li></ul></section><h2><a href="../index.html">In crate tracing_core</a></h2></div></nav><div class="sidebar-resizer"></div>
<main><div class="width-limiter"><nav class="sub"><form class="search-form"><span></span><div id="sidebar-button" tabindex="-1"><a href="../../tracing_core/all.html" title="show sidebar"></a></div><input class="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"><div id="help-button" tabindex="-1"><a href="../../help.html" title="help">?</a></div><div id="settings-menu" tabindex="-1"><a href="../../settings.html" title="settings"><img width="22" height="22" alt="Change settings" src="../../static.files/wheel-7b819b6101059cd0.svg"></a></div></form></nav><section id="main-content" class="content"><div class="main-heading"><h1>Module <a href="../index.html">tracing_core</a>::<wbr><a class="mod" href="#">callsite</a><button id="copy-path" title="Copy item path to clipboard"><img src="../../static.files/clipboard-7571035ce49a181d.svg" width="19" height="18" alt="Copy item path"></button></h1><span class="out-of-band"><a class="src" href="../../src/tracing_core/callsite.rs.html#1-619">source</a> · <button id="toggle-all-docs" title="collapse all docs">[<span>&#x2212;</span>]</button></span></div><details class="toggle top-doc" open><summary class="hideme"><span>Expand description</span></summary><div class="docblock"><p>Callsites represent the source locations from which spans or events
originate.</p>
<h2 id="what-are-callsites"><a class="doc-anchor" href="#what-are-callsites">§</a>What Are Callsites?</h2>
<p>Every span or event in <code>tracing</code> is associated with a <a href="../trait.Callsite.html" title="trait tracing_core::Callsite"><code>Callsite</code></a>. A
callsite is a small <code>static</code> value that is responsible for the following:</p>
<ul>
<li>Storing the span or event’s <a href="../struct.Metadata.html" title="struct tracing_core::Metadata"><code>Metadata</code></a>,</li>
<li>Uniquely <a href="struct.Identifier.html" title="struct tracing_core::callsite::Identifier">identifying</a> the span or event definition,</li>
<li>Caching the subscriber’s <a href="../subscriber/struct.Interest.html" title="struct tracing_core::subscriber::Interest"><code>Interest</code></a><sup id="fnref1"><a href="#fn1">1</a></sup> in that span or event, to avoid
re-evaluating filters.</li>
</ul>
<h2 id="registering-callsites"><a class="doc-anchor" href="#registering-callsites">§</a>Registering Callsites</h2>
<p>When a span or event is recorded for the first time, its callsite
<a href="fn.register.html" title="fn tracing_core::callsite::register"><code>register</code></a>s itself with the global callsite registry. Registering a
callsite calls the <a href="../trait.Subscriber.html#method.register_callsite" title="method tracing_core::Subscriber::register_callsite"><code>Subscriber::register_callsite</code></a>
method with that callsite’s <a href="../struct.Metadata.html" title="struct tracing_core::Metadata"><code>Metadata</code></a> on every currently active
subscriber. This serves two primary purposes: informing subscribers of the
callsite’s existence, and performing static filtering.</p>
<h3 id="callsite-existence"><a class="doc-anchor" href="#callsite-existence">§</a>Callsite Existence</h3>
<p>If a <a href="../trait.Subscriber.html" title="trait tracing_core::Subscriber"><code>Subscriber</code></a> implementation wishes to allocate storage for each
unique span/event location in the program, or pre-compute some value
that will be used to record that span or event in the future, it can
do so in its <a href="../trait.Subscriber.html#method.register_callsite" title="method tracing_core::Subscriber::register_callsite"><code>register_callsite</code></a> method.</p>
<h3 id="performing-static-filtering"><a class="doc-anchor" href="#performing-static-filtering">§</a>Performing Static Filtering</h3>
<p>The <a href="../trait.Subscriber.html#method.register_callsite" title="method tracing_core::Subscriber::register_callsite"><code>register_callsite</code></a> method returns an <a href="../subscriber/struct.Interest.html" title="struct tracing_core::subscriber::Interest"><code>Interest</code></a> value,
which indicates that the subscriber either <a href="../subscriber/struct.Interest.html#method.always" title="associated function tracing_core::subscriber::Interest::always">always</a> wishes to record
that span or event, <a href="../subscriber/struct.Interest.html#method.sometimes" title="associated function tracing_core::subscriber::Interest::sometimes">sometimes</a> wishes to record it based on a
dynamic filter evaluation, or <a href="../subscriber/struct.Interest.html#method.never" title="associated function tracing_core::subscriber::Interest::never">never</a> wishes to record it.</p>
<p>When registering a new callsite, the <a href="../subscriber/struct.Interest.html" title="struct tracing_core::subscriber::Interest"><code>Interest</code></a>s returned by every
currently active subscriber are combined, and the result is stored at
each callsite. This way, when the span or event occurs in the
future, the cached <a href="../subscriber/struct.Interest.html" title="struct tracing_core::subscriber::Interest"><code>Interest</code></a> value can be checked efficiently
to determine if the span or event should be recorded, without
needing to perform expensive filtering (i.e. calling the
<a href="../trait.Subscriber.html#tymethod.enabled" title="method tracing_core::Subscriber::enabled"><code>Subscriber::enabled</code></a> method every time a span or event occurs).</p>
<h4 id="rebuilding-cached-interest"><a class="doc-anchor" href="#rebuilding-cached-interest">§</a>Rebuilding Cached Interest</h4>
<p>When a new <a href="crate::dispatch::Dispatch"><code>Dispatch</code></a> is created (i.e. a new subscriber becomes
active), any previously cached <a href="../subscriber/struct.Interest.html" title="struct tracing_core::subscriber::Interest"><code>Interest</code></a> values are re-evaluated
for all callsites in the program. This way, if the new subscriber
will enable a callsite that was not previously enabled, the
<a href="../subscriber/struct.Interest.html" title="struct tracing_core::subscriber::Interest"><code>Interest</code></a> in that callsite is updated. Similarly, when a
subscriber is dropped, the interest cache is also re-evaluated, so
that any callsites enabled only by that subscriber are disabled.</p>
<p>In addition, the <a href="fn.rebuild_interest_cache.html" title="fn tracing_core::callsite::rebuild_interest_cache"><code>rebuild_interest_cache</code></a> function in this module can be
used to manually invalidate all cached interest and re-register those
callsites. This function is useful in situations where a subscriber’s
interest can change, but it does so relatively infrequently. The subscriber
may wish for its interest to be cached most of the time, and return
<a href="../subscriber/struct.Interest.html#method.always" title="associated function tracing_core::subscriber::Interest::always"><code>Interest::always</code></a> or <a href="../subscriber/struct.Interest.html#method.never" title="associated function tracing_core::subscriber::Interest::never"><code>Interest::never</code></a> in its
<a href="../trait.Subscriber.html#method.register_callsite" title="method tracing_core::Subscriber::register_callsite"><code>register_callsite</code></a> method, so that its <a href="../trait.Subscriber.html#tymethod.enabled" title="method tracing_core::Subscriber::enabled"><code>Subscriber::enabled</code></a> method
doesn’t need to be evaluated every time a span or event is recorded.
However, when the configuration changes, the subscriber can call
<a href="fn.rebuild_interest_cache.html" title="fn tracing_core::callsite::rebuild_interest_cache"><code>rebuild_interest_cache</code></a> to re-evaluate the entire interest cache with its
new configuration. This is a relatively costly operation, but if the
configuration changes infrequently, it may be more efficient than calling
<a href="../trait.Subscriber.html#tymethod.enabled" title="method tracing_core::Subscriber::enabled"><code>Subscriber::enabled</code></a> frequently.</p>
<h2 id="implementing-callsites"><a class="doc-anchor" href="#implementing-callsites">§</a>Implementing Callsites</h2>
<p>In most cases, instrumenting code using <code>tracing</code> should <em>not</em> require
implementing the <a href="../trait.Callsite.html" title="trait tracing_core::Callsite"><code>Callsite</code></a> trait directly. When using the <a href="https://docs.rs/tracing/latest/tracing/#macros"><code>tracing</code>
crate’s macros</a> or the <a href="https://docs.rs/tracing/latest/tracing/attr.instrument.html"><code>#[instrument]</code> attribute</a>, a
<code>Callsite</code> is automatically generated.</p>
<p>However, code which provides alternative forms of <code>tracing</code> instrumentation
may need to interact with the callsite system directly. If
instrumentation-side code needs to produce a <code>Callsite</code> to emit spans or
events, the <a href="struct.DefaultCallsite.html" title="struct tracing_core::callsite::DefaultCallsite"><code>DefaultCallsite</code></a> struct provided in this module is a
ready-made <code>Callsite</code> implementation that is suitable for most uses. When
possible, the use of <code>DefaultCallsite</code> should be preferred over implementing
<a href="../trait.Callsite.html" title="trait tracing_core::Callsite"><code>Callsite</code></a> for user types, as <code>DefaultCallsite</code> may benefit from
additional performance optimizations.</p>
<div class="footnotes"><hr><ol><li id="fn1"><p>Returned by the <a href="crate::subscriber::Subscriber::register_callsite"><code>Subscriber::register_callsite</code></a>
method.&nbsp;<a href="#fnref1">↩</a></p></li></ol></div></div></details><h2 id="structs" class="section-header">Structs<a href="#structs" class="anchor">§</a></h2><ul class="item-table"><li><div class="item-name"><a class="struct" href="struct.DefaultCallsite.html" title="struct tracing_core::callsite::DefaultCallsite">DefaultCallsite</a></div><div class="desc docblock-short">A default <a href="../trait.Callsite.html" title="trait tracing_core::Callsite"><code>Callsite</code></a> implementation.</div></li><li><div class="item-name"><a class="struct" href="struct.Identifier.html" title="struct tracing_core::callsite::Identifier">Identifier</a></div><div class="desc docblock-short">Uniquely identifies a <a href="../trait.Callsite.html" title="trait tracing_core::Callsite"><code>Callsite</code></a></div></li></ul><h2 id="traits" class="section-header">Traits<a href="#traits" class="anchor">§</a></h2><ul class="item-table"><li><div class="item-name"><a class="trait" href="trait.Callsite.html" title="trait tracing_core::callsite::Callsite">Callsite</a></div><div class="desc docblock-short">Trait implemented by callsites.</div></li></ul><h2 id="functions" class="section-header">Functions<a href="#functions" class="anchor">§</a></h2><ul class="item-table"><li><div class="item-name"><a class="fn" href="fn.rebuild_interest_cache.html" title="fn tracing_core::callsite::rebuild_interest_cache">rebuild_interest_cache</a></div><div class="desc docblock-short">Clear and reregister interest on every <a href="../trait.Callsite.html" title="trait tracing_core::Callsite"><code>Callsite</code></a></div></li><li><div class="item-name"><a class="fn" href="fn.register.html" title="fn tracing_core::callsite::register">register</a></div><div class="desc docblock-short">Register a new <a href="../trait.Callsite.html" title="trait tracing_core::Callsite"><code>Callsite</code></a> with the global registry.</div></li></ul></section></div></main></body></html>
Reference in a new issue View git blame Copy permalink