11cb0ef41Sopenharmony_ci<!DOCTYPE html> 21cb0ef41Sopenharmony_ci<html lang="en"> 31cb0ef41Sopenharmony_ci<head> 41cb0ef41Sopenharmony_ci <meta charset="utf-8"> 51cb0ef41Sopenharmony_ci <meta name="viewport" content="width=device-width"> 61cb0ef41Sopenharmony_ci <meta name="nodejs.org:node-version" content="v18.20.1"> 71cb0ef41Sopenharmony_ci <title>Diagnostics Channel | Node.js v18.20.1 Documentation</title> 81cb0ef41Sopenharmony_ci <link rel="stylesheet" href="https://fonts.googleapis.com/css?family=Lato:400,700,400italic&display=fallback"> 91cb0ef41Sopenharmony_ci <link rel="stylesheet" href="assets/style.css"> 101cb0ef41Sopenharmony_ci <link rel="stylesheet" href="assets/hljs.css"> 111cb0ef41Sopenharmony_ci <link rel="canonical" href="https://nodejs.org/api/diagnostics_channel.html"> 121cb0ef41Sopenharmony_ci <script async defer src="assets/api.js" type="text/javascript"></script> 131cb0ef41Sopenharmony_ci <style>@media(max-width:734px){.with-64-chars>.js-flavor-selector{float:none;margin:0 0 1em auto;}}</style> 141cb0ef41Sopenharmony_ci</head> 151cb0ef41Sopenharmony_ci<body class="alt apidoc" id="api-section-diagnostics_channel"> 161cb0ef41Sopenharmony_ci <div id="content" class="clearfix"> 171cb0ef41Sopenharmony_ci <div id="column2" class="interior"> 181cb0ef41Sopenharmony_ci <div id="intro" class="interior"> 191cb0ef41Sopenharmony_ci <a href="/" title="Go back to the home page"> 201cb0ef41Sopenharmony_ci Node.js 211cb0ef41Sopenharmony_ci </a> 221cb0ef41Sopenharmony_ci </div> 231cb0ef41Sopenharmony_ci <ul> 241cb0ef41Sopenharmony_ci<li><a href="documentation.html" class="nav-documentation">About this documentation</a></li> 251cb0ef41Sopenharmony_ci<li><a href="synopsis.html" class="nav-synopsis">Usage and example</a></li> 261cb0ef41Sopenharmony_ci</ul> 271cb0ef41Sopenharmony_ci<hr class="line"> 281cb0ef41Sopenharmony_ci<ul> 291cb0ef41Sopenharmony_ci<li><a href="assert.html" class="nav-assert">Assertion testing</a></li> 301cb0ef41Sopenharmony_ci<li><a href="async_context.html" class="nav-async_context">Asynchronous context tracking</a></li> 311cb0ef41Sopenharmony_ci<li><a href="async_hooks.html" class="nav-async_hooks">Async hooks</a></li> 321cb0ef41Sopenharmony_ci<li><a href="buffer.html" class="nav-buffer">Buffer</a></li> 331cb0ef41Sopenharmony_ci<li><a href="addons.html" class="nav-addons">C++ addons</a></li> 341cb0ef41Sopenharmony_ci<li><a href="n-api.html" class="nav-n-api">C/C++ addons with Node-API</a></li> 351cb0ef41Sopenharmony_ci<li><a href="embedding.html" class="nav-embedding">C++ embedder API</a></li> 361cb0ef41Sopenharmony_ci<li><a href="child_process.html" class="nav-child_process">Child processes</a></li> 371cb0ef41Sopenharmony_ci<li><a href="cluster.html" class="nav-cluster">Cluster</a></li> 381cb0ef41Sopenharmony_ci<li><a href="cli.html" class="nav-cli">Command-line options</a></li> 391cb0ef41Sopenharmony_ci<li><a href="console.html" class="nav-console">Console</a></li> 401cb0ef41Sopenharmony_ci<li><a href="corepack.html" class="nav-corepack">Corepack</a></li> 411cb0ef41Sopenharmony_ci<li><a href="crypto.html" class="nav-crypto">Crypto</a></li> 421cb0ef41Sopenharmony_ci<li><a href="debugger.html" class="nav-debugger">Debugger</a></li> 431cb0ef41Sopenharmony_ci<li><a href="deprecations.html" class="nav-deprecations">Deprecated APIs</a></li> 441cb0ef41Sopenharmony_ci<li><a href="diagnostics_channel.html" class="nav-diagnostics_channel active">Diagnostics Channel</a></li> 451cb0ef41Sopenharmony_ci<li><a href="dns.html" class="nav-dns">DNS</a></li> 461cb0ef41Sopenharmony_ci<li><a href="domain.html" class="nav-domain">Domain</a></li> 471cb0ef41Sopenharmony_ci<li><a href="errors.html" class="nav-errors">Errors</a></li> 481cb0ef41Sopenharmony_ci<li><a href="events.html" class="nav-events">Events</a></li> 491cb0ef41Sopenharmony_ci<li><a href="fs.html" class="nav-fs">File system</a></li> 501cb0ef41Sopenharmony_ci<li><a href="globals.html" class="nav-globals">Globals</a></li> 511cb0ef41Sopenharmony_ci<li><a href="http.html" class="nav-http">HTTP</a></li> 521cb0ef41Sopenharmony_ci<li><a href="http2.html" class="nav-http2">HTTP/2</a></li> 531cb0ef41Sopenharmony_ci<li><a href="https.html" class="nav-https">HTTPS</a></li> 541cb0ef41Sopenharmony_ci<li><a href="inspector.html" class="nav-inspector">Inspector</a></li> 551cb0ef41Sopenharmony_ci<li><a href="intl.html" class="nav-intl">Internationalization</a></li> 561cb0ef41Sopenharmony_ci<li><a href="modules.html" class="nav-modules">Modules: CommonJS modules</a></li> 571cb0ef41Sopenharmony_ci<li><a href="esm.html" class="nav-esm">Modules: ECMAScript modules</a></li> 581cb0ef41Sopenharmony_ci<li><a href="module.html" class="nav-module">Modules: <code>node:module</code> API</a></li> 591cb0ef41Sopenharmony_ci<li><a href="packages.html" class="nav-packages">Modules: Packages</a></li> 601cb0ef41Sopenharmony_ci<li><a href="net.html" class="nav-net">Net</a></li> 611cb0ef41Sopenharmony_ci<li><a href="os.html" class="nav-os">OS</a></li> 621cb0ef41Sopenharmony_ci<li><a href="path.html" class="nav-path">Path</a></li> 631cb0ef41Sopenharmony_ci<li><a href="perf_hooks.html" class="nav-perf_hooks">Performance hooks</a></li> 641cb0ef41Sopenharmony_ci<li><a href="permissions.html" class="nav-permissions">Permissions</a></li> 651cb0ef41Sopenharmony_ci<li><a href="process.html" class="nav-process">Process</a></li> 661cb0ef41Sopenharmony_ci<li><a href="punycode.html" class="nav-punycode">Punycode</a></li> 671cb0ef41Sopenharmony_ci<li><a href="querystring.html" class="nav-querystring">Query strings</a></li> 681cb0ef41Sopenharmony_ci<li><a href="readline.html" class="nav-readline">Readline</a></li> 691cb0ef41Sopenharmony_ci<li><a href="repl.html" class="nav-repl">REPL</a></li> 701cb0ef41Sopenharmony_ci<li><a href="report.html" class="nav-report">Report</a></li> 711cb0ef41Sopenharmony_ci<li><a href="single-executable-applications.html" class="nav-single-executable-applications">Single executable applications</a></li> 721cb0ef41Sopenharmony_ci<li><a href="stream.html" class="nav-stream">Stream</a></li> 731cb0ef41Sopenharmony_ci<li><a href="string_decoder.html" class="nav-string_decoder">String decoder</a></li> 741cb0ef41Sopenharmony_ci<li><a href="test.html" class="nav-test">Test runner</a></li> 751cb0ef41Sopenharmony_ci<li><a href="timers.html" class="nav-timers">Timers</a></li> 761cb0ef41Sopenharmony_ci<li><a href="tls.html" class="nav-tls">TLS/SSL</a></li> 771cb0ef41Sopenharmony_ci<li><a href="tracing.html" class="nav-tracing">Trace events</a></li> 781cb0ef41Sopenharmony_ci<li><a href="tty.html" class="nav-tty">TTY</a></li> 791cb0ef41Sopenharmony_ci<li><a href="dgram.html" class="nav-dgram">UDP/datagram</a></li> 801cb0ef41Sopenharmony_ci<li><a href="url.html" class="nav-url">URL</a></li> 811cb0ef41Sopenharmony_ci<li><a href="util.html" class="nav-util">Utilities</a></li> 821cb0ef41Sopenharmony_ci<li><a href="v8.html" class="nav-v8">V8</a></li> 831cb0ef41Sopenharmony_ci<li><a href="vm.html" class="nav-vm">VM</a></li> 841cb0ef41Sopenharmony_ci<li><a href="wasi.html" class="nav-wasi">WASI</a></li> 851cb0ef41Sopenharmony_ci<li><a href="webcrypto.html" class="nav-webcrypto">Web Crypto API</a></li> 861cb0ef41Sopenharmony_ci<li><a href="webstreams.html" class="nav-webstreams">Web Streams API</a></li> 871cb0ef41Sopenharmony_ci<li><a href="worker_threads.html" class="nav-worker_threads">Worker threads</a></li> 881cb0ef41Sopenharmony_ci<li><a href="zlib.html" class="nav-zlib">Zlib</a></li> 891cb0ef41Sopenharmony_ci</ul> 901cb0ef41Sopenharmony_ci<hr class="line"> 911cb0ef41Sopenharmony_ci<ul> 921cb0ef41Sopenharmony_ci<li><a href="https://github.com/nodejs/node" class="nav-https-github-com-nodejs-node">Code repository and issue tracker</a></li> 931cb0ef41Sopenharmony_ci</ul> 941cb0ef41Sopenharmony_ci </div> 951cb0ef41Sopenharmony_ci 961cb0ef41Sopenharmony_ci <div id="column1" data-id="diagnostics_channel" class="interior"> 971cb0ef41Sopenharmony_ci <header class="header"> 981cb0ef41Sopenharmony_ci <div class="header-container"> 991cb0ef41Sopenharmony_ci <h1>Node.js v18.20.1 documentation</h1> 1001cb0ef41Sopenharmony_ci <button class="theme-toggle-btn" id="theme-toggle-btn" title="Toggle dark mode/light mode" aria-label="Toggle dark mode/light mode" hidden> 1011cb0ef41Sopenharmony_ci <svg xmlns="http://www.w3.org/2000/svg" class="icon dark-icon" height="24" width="24"> 1021cb0ef41Sopenharmony_ci <path fill="none" d="M0 0h24v24H0z" /> 1031cb0ef41Sopenharmony_ci <path d="M11.1 12.08c-2.33-4.51-.5-8.48.53-10.07C6.27 2.2 1.98 6.59 1.98 12c0 .14.02.28.02.42.62-.27 1.29-.42 2-.42 1.66 0 3.18.83 4.1 2.15A4.01 4.01 0 0111 18c0 1.52-.87 2.83-2.12 3.51.98.32 2.03.5 3.11.5 3.5 0 6.58-1.8 8.37-4.52-2.36.23-6.98-.97-9.26-5.41z"/> 1041cb0ef41Sopenharmony_ci <path d="M7 16h-.18C6.4 14.84 5.3 14 4 14c-1.66 0-3 1.34-3 3s1.34 3 3 3h3c1.1 0 2-.9 2-2s-.9-2-2-2z"/> 1051cb0ef41Sopenharmony_ci </svg> 1061cb0ef41Sopenharmony_ci <svg xmlns="http://www.w3.org/2000/svg" class="icon light-icon" height="24" width="24"> 1071cb0ef41Sopenharmony_ci <path d="M0 0h24v24H0z" fill="none" /> 1081cb0ef41Sopenharmony_ci <path d="M6.76 4.84l-1.8-1.79-1.41 1.41 1.79 1.79 1.42-1.41zM4 10.5H1v2h3v-2zm9-9.95h-2V3.5h2V.55zm7.45 3.91l-1.41-1.41-1.79 1.79 1.41 1.41 1.79-1.79zm-3.21 13.7l1.79 1.8 1.41-1.41-1.8-1.79-1.4 1.4zM20 10.5v2h3v-2h-3zm-8-5c-3.31 0-6 2.69-6 6s2.69 6 6 6 6-2.69 6-6-2.69-6-6-6zm-1 16.95h2V19.5h-2v2.95zm-7.45-3.91l1.41 1.41 1.79-1.8-1.41-1.41-1.79 1.8z"/> 1091cb0ef41Sopenharmony_ci </svg> 1101cb0ef41Sopenharmony_ci </button> 1111cb0ef41Sopenharmony_ci </div> 1121cb0ef41Sopenharmony_ci <div id="gtoc"> 1131cb0ef41Sopenharmony_ci <ul> 1141cb0ef41Sopenharmony_ci <li class="pinned-header">Node.js v18.20.1</li> 1151cb0ef41Sopenharmony_ci 1161cb0ef41Sopenharmony_ci <li class="picker-header"> 1171cb0ef41Sopenharmony_ci <a href="#"> 1181cb0ef41Sopenharmony_ci <span class="collapsed-arrow">►</span><span class="expanded-arrow">▼</span> 1191cb0ef41Sopenharmony_ci Table of contents 1201cb0ef41Sopenharmony_ci </a> 1211cb0ef41Sopenharmony_ci 1221cb0ef41Sopenharmony_ci <div class="picker"><div class="toc"><ul> 1231cb0ef41Sopenharmony_ci<li><span class="stability_2"><a href="#diagnostics-channel">Diagnostics Channel</a></span> 1241cb0ef41Sopenharmony_ci<ul> 1251cb0ef41Sopenharmony_ci<li><a href="#public-api">Public API</a> 1261cb0ef41Sopenharmony_ci<ul> 1271cb0ef41Sopenharmony_ci<li><a href="#overview">Overview</a> 1281cb0ef41Sopenharmony_ci<ul> 1291cb0ef41Sopenharmony_ci<li><a href="#diagnostics_channelhassubscribersname"><code>diagnostics_channel.hasSubscribers(name)</code></a></li> 1301cb0ef41Sopenharmony_ci<li><a href="#diagnostics_channelchannelname"><code>diagnostics_channel.channel(name)</code></a></li> 1311cb0ef41Sopenharmony_ci<li><a href="#diagnostics_channelsubscribename-onmessage"><code>diagnostics_channel.subscribe(name, onMessage)</code></a></li> 1321cb0ef41Sopenharmony_ci<li><a href="#diagnostics_channelunsubscribename-onmessage"><code>diagnostics_channel.unsubscribe(name, onMessage)</code></a></li> 1331cb0ef41Sopenharmony_ci<li><span class="stability_1"><a href="#diagnostics_channeltracingchannelnameorchannels"><code>diagnostics_channel.tracingChannel(nameOrChannels)</code></a></span></li> 1341cb0ef41Sopenharmony_ci</ul> 1351cb0ef41Sopenharmony_ci</li> 1361cb0ef41Sopenharmony_ci<li><a href="#class-channel">Class: <code>Channel</code></a> 1371cb0ef41Sopenharmony_ci<ul> 1381cb0ef41Sopenharmony_ci<li><a href="#channelhassubscribers"><code>channel.hasSubscribers</code></a></li> 1391cb0ef41Sopenharmony_ci<li><a href="#channelpublishmessage"><code>channel.publish(message)</code></a></li> 1401cb0ef41Sopenharmony_ci<li><span class="stability_0"><a href="#channelsubscribeonmessage"><code>channel.subscribe(onMessage)</code></a></span></li> 1411cb0ef41Sopenharmony_ci<li><span class="stability_0"><a href="#channelunsubscribeonmessage"><code>channel.unsubscribe(onMessage)</code></a></span></li> 1421cb0ef41Sopenharmony_ci<li><span class="stability_1"><a href="#channelbindstorestore-transform"><code>channel.bindStore(store[, transform])</code></a></span></li> 1431cb0ef41Sopenharmony_ci<li><span class="stability_1"><a href="#channelunbindstorestore"><code>channel.unbindStore(store)</code></a></span></li> 1441cb0ef41Sopenharmony_ci<li><span class="stability_1"><a href="#channelrunstorescontext-fn-thisarg-args"><code>channel.runStores(context, fn[, thisArg[, ...args]])</code></a></span></li> 1451cb0ef41Sopenharmony_ci</ul> 1461cb0ef41Sopenharmony_ci</li> 1471cb0ef41Sopenharmony_ci<li><span class="stability_1"><a href="#class-tracingchannel">Class: <code>TracingChannel</code></a></span> 1481cb0ef41Sopenharmony_ci<ul> 1491cb0ef41Sopenharmony_ci<li><span class="stability_1"><a href="#tracingchannelsubscribesubscribers"><code>tracingChannel.subscribe(subscribers)</code></a></span></li> 1501cb0ef41Sopenharmony_ci<li><span class="stability_1"><a href="#tracingchannelunsubscribesubscribers"><code>tracingChannel.unsubscribe(subscribers)</code></a></span></li> 1511cb0ef41Sopenharmony_ci<li><span class="stability_1"><a href="#tracingchanneltracesyncfn-context-thisarg-args"><code>tracingChannel.traceSync(fn[, context[, thisArg[, ...args]]])</code></a></span></li> 1521cb0ef41Sopenharmony_ci<li><span class="stability_1"><a href="#tracingchanneltracepromisefn-context-thisarg-args"><code>tracingChannel.tracePromise(fn[, context[, thisArg[, ...args]]])</code></a></span></li> 1531cb0ef41Sopenharmony_ci<li><span class="stability_1"><a href="#tracingchanneltracecallbackfn-position-context-thisarg-args"><code>tracingChannel.traceCallback(fn[, position[, context[, thisArg[, ...args]]]])</code></a></span></li> 1541cb0ef41Sopenharmony_ci</ul> 1551cb0ef41Sopenharmony_ci</li> 1561cb0ef41Sopenharmony_ci<li><a href="#tracingchannel-channels">TracingChannel Channels</a> 1571cb0ef41Sopenharmony_ci<ul> 1581cb0ef41Sopenharmony_ci<li><a href="#startevent"><code>start(event)</code></a></li> 1591cb0ef41Sopenharmony_ci<li><a href="#endevent"><code>end(event)</code></a></li> 1601cb0ef41Sopenharmony_ci<li><a href="#asyncstartevent"><code>asyncStart(event)</code></a></li> 1611cb0ef41Sopenharmony_ci<li><a href="#asyncendevent"><code>asyncEnd(event)</code></a></li> 1621cb0ef41Sopenharmony_ci<li><a href="#errorevent"><code>error(event)</code></a></li> 1631cb0ef41Sopenharmony_ci</ul> 1641cb0ef41Sopenharmony_ci</li> 1651cb0ef41Sopenharmony_ci<li><span class="stability_1"><a href="#built-in-channels">Built-in Channels</a></span> 1661cb0ef41Sopenharmony_ci<ul> 1671cb0ef41Sopenharmony_ci<li><a href="#http">HTTP</a></li> 1681cb0ef41Sopenharmony_ci</ul> 1691cb0ef41Sopenharmony_ci</li> 1701cb0ef41Sopenharmony_ci</ul> 1711cb0ef41Sopenharmony_ci</li> 1721cb0ef41Sopenharmony_ci</ul> 1731cb0ef41Sopenharmony_ci</li> 1741cb0ef41Sopenharmony_ci</ul></div></div> 1751cb0ef41Sopenharmony_ci </li> 1761cb0ef41Sopenharmony_ci 1771cb0ef41Sopenharmony_ci 1781cb0ef41Sopenharmony_ci <li class="picker-header"> 1791cb0ef41Sopenharmony_ci <a href="#"> 1801cb0ef41Sopenharmony_ci <span class="collapsed-arrow">►</span><span class="expanded-arrow">▼</span> 1811cb0ef41Sopenharmony_ci Index 1821cb0ef41Sopenharmony_ci </a> 1831cb0ef41Sopenharmony_ci 1841cb0ef41Sopenharmony_ci <div class="picker"><ul> 1851cb0ef41Sopenharmony_ci<li><a href="documentation.html" class="nav-documentation">About this documentation</a></li> 1861cb0ef41Sopenharmony_ci<li><a href="synopsis.html" class="nav-synopsis">Usage and example</a></li> 1871cb0ef41Sopenharmony_ci 1881cb0ef41Sopenharmony_ci <li> 1891cb0ef41Sopenharmony_ci <a href="index.html">Index</a> 1901cb0ef41Sopenharmony_ci </li> 1911cb0ef41Sopenharmony_ci </ul> 1921cb0ef41Sopenharmony_ci 1931cb0ef41Sopenharmony_ci<hr class="line"> 1941cb0ef41Sopenharmony_ci<ul> 1951cb0ef41Sopenharmony_ci<li><a href="assert.html" class="nav-assert">Assertion testing</a></li> 1961cb0ef41Sopenharmony_ci<li><a href="async_context.html" class="nav-async_context">Asynchronous context tracking</a></li> 1971cb0ef41Sopenharmony_ci<li><a href="async_hooks.html" class="nav-async_hooks">Async hooks</a></li> 1981cb0ef41Sopenharmony_ci<li><a href="buffer.html" class="nav-buffer">Buffer</a></li> 1991cb0ef41Sopenharmony_ci<li><a href="addons.html" class="nav-addons">C++ addons</a></li> 2001cb0ef41Sopenharmony_ci<li><a href="n-api.html" class="nav-n-api">C/C++ addons with Node-API</a></li> 2011cb0ef41Sopenharmony_ci<li><a href="embedding.html" class="nav-embedding">C++ embedder API</a></li> 2021cb0ef41Sopenharmony_ci<li><a href="child_process.html" class="nav-child_process">Child processes</a></li> 2031cb0ef41Sopenharmony_ci<li><a href="cluster.html" class="nav-cluster">Cluster</a></li> 2041cb0ef41Sopenharmony_ci<li><a href="cli.html" class="nav-cli">Command-line options</a></li> 2051cb0ef41Sopenharmony_ci<li><a href="console.html" class="nav-console">Console</a></li> 2061cb0ef41Sopenharmony_ci<li><a href="corepack.html" class="nav-corepack">Corepack</a></li> 2071cb0ef41Sopenharmony_ci<li><a href="crypto.html" class="nav-crypto">Crypto</a></li> 2081cb0ef41Sopenharmony_ci<li><a href="debugger.html" class="nav-debugger">Debugger</a></li> 2091cb0ef41Sopenharmony_ci<li><a href="deprecations.html" class="nav-deprecations">Deprecated APIs</a></li> 2101cb0ef41Sopenharmony_ci<li><a href="diagnostics_channel.html" class="nav-diagnostics_channel active">Diagnostics Channel</a></li> 2111cb0ef41Sopenharmony_ci<li><a href="dns.html" class="nav-dns">DNS</a></li> 2121cb0ef41Sopenharmony_ci<li><a href="domain.html" class="nav-domain">Domain</a></li> 2131cb0ef41Sopenharmony_ci<li><a href="errors.html" class="nav-errors">Errors</a></li> 2141cb0ef41Sopenharmony_ci<li><a href="events.html" class="nav-events">Events</a></li> 2151cb0ef41Sopenharmony_ci<li><a href="fs.html" class="nav-fs">File system</a></li> 2161cb0ef41Sopenharmony_ci<li><a href="globals.html" class="nav-globals">Globals</a></li> 2171cb0ef41Sopenharmony_ci<li><a href="http.html" class="nav-http">HTTP</a></li> 2181cb0ef41Sopenharmony_ci<li><a href="http2.html" class="nav-http2">HTTP/2</a></li> 2191cb0ef41Sopenharmony_ci<li><a href="https.html" class="nav-https">HTTPS</a></li> 2201cb0ef41Sopenharmony_ci<li><a href="inspector.html" class="nav-inspector">Inspector</a></li> 2211cb0ef41Sopenharmony_ci<li><a href="intl.html" class="nav-intl">Internationalization</a></li> 2221cb0ef41Sopenharmony_ci<li><a href="modules.html" class="nav-modules">Modules: CommonJS modules</a></li> 2231cb0ef41Sopenharmony_ci<li><a href="esm.html" class="nav-esm">Modules: ECMAScript modules</a></li> 2241cb0ef41Sopenharmony_ci<li><a href="module.html" class="nav-module">Modules: <code>node:module</code> API</a></li> 2251cb0ef41Sopenharmony_ci<li><a href="packages.html" class="nav-packages">Modules: Packages</a></li> 2261cb0ef41Sopenharmony_ci<li><a href="net.html" class="nav-net">Net</a></li> 2271cb0ef41Sopenharmony_ci<li><a href="os.html" class="nav-os">OS</a></li> 2281cb0ef41Sopenharmony_ci<li><a href="path.html" class="nav-path">Path</a></li> 2291cb0ef41Sopenharmony_ci<li><a href="perf_hooks.html" class="nav-perf_hooks">Performance hooks</a></li> 2301cb0ef41Sopenharmony_ci<li><a href="permissions.html" class="nav-permissions">Permissions</a></li> 2311cb0ef41Sopenharmony_ci<li><a href="process.html" class="nav-process">Process</a></li> 2321cb0ef41Sopenharmony_ci<li><a href="punycode.html" class="nav-punycode">Punycode</a></li> 2331cb0ef41Sopenharmony_ci<li><a href="querystring.html" class="nav-querystring">Query strings</a></li> 2341cb0ef41Sopenharmony_ci<li><a href="readline.html" class="nav-readline">Readline</a></li> 2351cb0ef41Sopenharmony_ci<li><a href="repl.html" class="nav-repl">REPL</a></li> 2361cb0ef41Sopenharmony_ci<li><a href="report.html" class="nav-report">Report</a></li> 2371cb0ef41Sopenharmony_ci<li><a href="single-executable-applications.html" class="nav-single-executable-applications">Single executable applications</a></li> 2381cb0ef41Sopenharmony_ci<li><a href="stream.html" class="nav-stream">Stream</a></li> 2391cb0ef41Sopenharmony_ci<li><a href="string_decoder.html" class="nav-string_decoder">String decoder</a></li> 2401cb0ef41Sopenharmony_ci<li><a href="test.html" class="nav-test">Test runner</a></li> 2411cb0ef41Sopenharmony_ci<li><a href="timers.html" class="nav-timers">Timers</a></li> 2421cb0ef41Sopenharmony_ci<li><a href="tls.html" class="nav-tls">TLS/SSL</a></li> 2431cb0ef41Sopenharmony_ci<li><a href="tracing.html" class="nav-tracing">Trace events</a></li> 2441cb0ef41Sopenharmony_ci<li><a href="tty.html" class="nav-tty">TTY</a></li> 2451cb0ef41Sopenharmony_ci<li><a href="dgram.html" class="nav-dgram">UDP/datagram</a></li> 2461cb0ef41Sopenharmony_ci<li><a href="url.html" class="nav-url">URL</a></li> 2471cb0ef41Sopenharmony_ci<li><a href="util.html" class="nav-util">Utilities</a></li> 2481cb0ef41Sopenharmony_ci<li><a href="v8.html" class="nav-v8">V8</a></li> 2491cb0ef41Sopenharmony_ci<li><a href="vm.html" class="nav-vm">VM</a></li> 2501cb0ef41Sopenharmony_ci<li><a href="wasi.html" class="nav-wasi">WASI</a></li> 2511cb0ef41Sopenharmony_ci<li><a href="webcrypto.html" class="nav-webcrypto">Web Crypto API</a></li> 2521cb0ef41Sopenharmony_ci<li><a href="webstreams.html" class="nav-webstreams">Web Streams API</a></li> 2531cb0ef41Sopenharmony_ci<li><a href="worker_threads.html" class="nav-worker_threads">Worker threads</a></li> 2541cb0ef41Sopenharmony_ci<li><a href="zlib.html" class="nav-zlib">Zlib</a></li> 2551cb0ef41Sopenharmony_ci</ul> 2561cb0ef41Sopenharmony_ci<hr class="line"> 2571cb0ef41Sopenharmony_ci<ul> 2581cb0ef41Sopenharmony_ci<li><a href="https://github.com/nodejs/node" class="nav-https-github-com-nodejs-node">Code repository and issue tracker</a></li> 2591cb0ef41Sopenharmony_ci</ul></div> 2601cb0ef41Sopenharmony_ci </li> 2611cb0ef41Sopenharmony_ci 2621cb0ef41Sopenharmony_ci 2631cb0ef41Sopenharmony_ci <li class="picker-header"> 2641cb0ef41Sopenharmony_ci <a href="#"> 2651cb0ef41Sopenharmony_ci <span class="collapsed-arrow">►</span><span class="expanded-arrow">▼</span> 2661cb0ef41Sopenharmony_ci Other versions 2671cb0ef41Sopenharmony_ci </a> 2681cb0ef41Sopenharmony_ci <div class="picker"><ol id="alt-docs"><li><a href="https://nodejs.org/docs/latest-v21.x/api/diagnostics_channel.html">21.x</a></li> 2691cb0ef41Sopenharmony_ci<li><a href="https://nodejs.org/docs/latest-v20.x/api/diagnostics_channel.html">20.x <b>LTS</b></a></li> 2701cb0ef41Sopenharmony_ci<li><a href="https://nodejs.org/docs/latest-v19.x/api/diagnostics_channel.html">19.x</a></li> 2711cb0ef41Sopenharmony_ci<li><a href="https://nodejs.org/docs/latest-v18.x/api/diagnostics_channel.html">18.x <b>LTS</b></a></li> 2721cb0ef41Sopenharmony_ci<li><a href="https://nodejs.org/docs/latest-v17.x/api/diagnostics_channel.html">17.x</a></li> 2731cb0ef41Sopenharmony_ci<li><a href="https://nodejs.org/docs/latest-v16.x/api/diagnostics_channel.html">16.x</a></li> 2741cb0ef41Sopenharmony_ci<li><a href="https://nodejs.org/docs/latest-v15.x/api/diagnostics_channel.html">15.x</a></li></ol></div> 2751cb0ef41Sopenharmony_ci </li> 2761cb0ef41Sopenharmony_ci 2771cb0ef41Sopenharmony_ci <li class="picker-header"> 2781cb0ef41Sopenharmony_ci <a href="#"> 2791cb0ef41Sopenharmony_ci <span class="collapsed-arrow">►</span><span class="expanded-arrow">▼</span> 2801cb0ef41Sopenharmony_ci Options 2811cb0ef41Sopenharmony_ci </a> 2821cb0ef41Sopenharmony_ci 2831cb0ef41Sopenharmony_ci <div class="picker"> 2841cb0ef41Sopenharmony_ci <ul> 2851cb0ef41Sopenharmony_ci <li> 2861cb0ef41Sopenharmony_ci <a href="all.html">View on single page</a> 2871cb0ef41Sopenharmony_ci </li> 2881cb0ef41Sopenharmony_ci <li> 2891cb0ef41Sopenharmony_ci <a href="diagnostics_channel.json">View as JSON</a> 2901cb0ef41Sopenharmony_ci </li> 2911cb0ef41Sopenharmony_ci <li class="edit_on_github"><a href="https://github.com/nodejs/node/edit/main/doc/api/diagnostics_channel.md">Edit on GitHub</a></li> 2921cb0ef41Sopenharmony_ci </ul> 2931cb0ef41Sopenharmony_ci </div> 2941cb0ef41Sopenharmony_ci </li> 2951cb0ef41Sopenharmony_ci </ul> 2961cb0ef41Sopenharmony_ci </div> 2971cb0ef41Sopenharmony_ci <hr> 2981cb0ef41Sopenharmony_ci </header> 2991cb0ef41Sopenharmony_ci 3001cb0ef41Sopenharmony_ci <details id="toc" open><summary>Table of contents</summary><ul> 3011cb0ef41Sopenharmony_ci<li><span class="stability_2"><a href="#diagnostics-channel">Diagnostics Channel</a></span> 3021cb0ef41Sopenharmony_ci<ul> 3031cb0ef41Sopenharmony_ci<li><a href="#public-api">Public API</a> 3041cb0ef41Sopenharmony_ci<ul> 3051cb0ef41Sopenharmony_ci<li><a href="#overview">Overview</a> 3061cb0ef41Sopenharmony_ci<ul> 3071cb0ef41Sopenharmony_ci<li><a href="#diagnostics_channelhassubscribersname"><code>diagnostics_channel.hasSubscribers(name)</code></a></li> 3081cb0ef41Sopenharmony_ci<li><a href="#diagnostics_channelchannelname"><code>diagnostics_channel.channel(name)</code></a></li> 3091cb0ef41Sopenharmony_ci<li><a href="#diagnostics_channelsubscribename-onmessage"><code>diagnostics_channel.subscribe(name, onMessage)</code></a></li> 3101cb0ef41Sopenharmony_ci<li><a href="#diagnostics_channelunsubscribename-onmessage"><code>diagnostics_channel.unsubscribe(name, onMessage)</code></a></li> 3111cb0ef41Sopenharmony_ci<li><span class="stability_1"><a href="#diagnostics_channeltracingchannelnameorchannels"><code>diagnostics_channel.tracingChannel(nameOrChannels)</code></a></span></li> 3121cb0ef41Sopenharmony_ci</ul> 3131cb0ef41Sopenharmony_ci</li> 3141cb0ef41Sopenharmony_ci<li><a href="#class-channel">Class: <code>Channel</code></a> 3151cb0ef41Sopenharmony_ci<ul> 3161cb0ef41Sopenharmony_ci<li><a href="#channelhassubscribers"><code>channel.hasSubscribers</code></a></li> 3171cb0ef41Sopenharmony_ci<li><a href="#channelpublishmessage"><code>channel.publish(message)</code></a></li> 3181cb0ef41Sopenharmony_ci<li><span class="stability_0"><a href="#channelsubscribeonmessage"><code>channel.subscribe(onMessage)</code></a></span></li> 3191cb0ef41Sopenharmony_ci<li><span class="stability_0"><a href="#channelunsubscribeonmessage"><code>channel.unsubscribe(onMessage)</code></a></span></li> 3201cb0ef41Sopenharmony_ci<li><span class="stability_1"><a href="#channelbindstorestore-transform"><code>channel.bindStore(store[, transform])</code></a></span></li> 3211cb0ef41Sopenharmony_ci<li><span class="stability_1"><a href="#channelunbindstorestore"><code>channel.unbindStore(store)</code></a></span></li> 3221cb0ef41Sopenharmony_ci<li><span class="stability_1"><a href="#channelrunstorescontext-fn-thisarg-args"><code>channel.runStores(context, fn[, thisArg[, ...args]])</code></a></span></li> 3231cb0ef41Sopenharmony_ci</ul> 3241cb0ef41Sopenharmony_ci</li> 3251cb0ef41Sopenharmony_ci<li><span class="stability_1"><a href="#class-tracingchannel">Class: <code>TracingChannel</code></a></span> 3261cb0ef41Sopenharmony_ci<ul> 3271cb0ef41Sopenharmony_ci<li><span class="stability_1"><a href="#tracingchannelsubscribesubscribers"><code>tracingChannel.subscribe(subscribers)</code></a></span></li> 3281cb0ef41Sopenharmony_ci<li><span class="stability_1"><a href="#tracingchannelunsubscribesubscribers"><code>tracingChannel.unsubscribe(subscribers)</code></a></span></li> 3291cb0ef41Sopenharmony_ci<li><span class="stability_1"><a href="#tracingchanneltracesyncfn-context-thisarg-args"><code>tracingChannel.traceSync(fn[, context[, thisArg[, ...args]]])</code></a></span></li> 3301cb0ef41Sopenharmony_ci<li><span class="stability_1"><a href="#tracingchanneltracepromisefn-context-thisarg-args"><code>tracingChannel.tracePromise(fn[, context[, thisArg[, ...args]]])</code></a></span></li> 3311cb0ef41Sopenharmony_ci<li><span class="stability_1"><a href="#tracingchanneltracecallbackfn-position-context-thisarg-args"><code>tracingChannel.traceCallback(fn[, position[, context[, thisArg[, ...args]]]])</code></a></span></li> 3321cb0ef41Sopenharmony_ci</ul> 3331cb0ef41Sopenharmony_ci</li> 3341cb0ef41Sopenharmony_ci<li><a href="#tracingchannel-channels">TracingChannel Channels</a> 3351cb0ef41Sopenharmony_ci<ul> 3361cb0ef41Sopenharmony_ci<li><a href="#startevent"><code>start(event)</code></a></li> 3371cb0ef41Sopenharmony_ci<li><a href="#endevent"><code>end(event)</code></a></li> 3381cb0ef41Sopenharmony_ci<li><a href="#asyncstartevent"><code>asyncStart(event)</code></a></li> 3391cb0ef41Sopenharmony_ci<li><a href="#asyncendevent"><code>asyncEnd(event)</code></a></li> 3401cb0ef41Sopenharmony_ci<li><a href="#errorevent"><code>error(event)</code></a></li> 3411cb0ef41Sopenharmony_ci</ul> 3421cb0ef41Sopenharmony_ci</li> 3431cb0ef41Sopenharmony_ci<li><span class="stability_1"><a href="#built-in-channels">Built-in Channels</a></span> 3441cb0ef41Sopenharmony_ci<ul> 3451cb0ef41Sopenharmony_ci<li><a href="#http">HTTP</a></li> 3461cb0ef41Sopenharmony_ci</ul> 3471cb0ef41Sopenharmony_ci</li> 3481cb0ef41Sopenharmony_ci</ul> 3491cb0ef41Sopenharmony_ci</li> 3501cb0ef41Sopenharmony_ci</ul> 3511cb0ef41Sopenharmony_ci</li> 3521cb0ef41Sopenharmony_ci</ul></details> 3531cb0ef41Sopenharmony_ci 3541cb0ef41Sopenharmony_ci <div id="apicontent"> 3551cb0ef41Sopenharmony_ci <h2>Diagnostics Channel<span><a class="mark" href="#diagnostics-channel" id="diagnostics-channel">#</a></span><a aria-hidden="true" class="legacy" id="diagnostics_channel_diagnostics_channel"></a></h2> 3561cb0ef41Sopenharmony_ci<div class="api_metadata"> 3571cb0ef41Sopenharmony_ci<details class="changelog"><summary>History</summary> 3581cb0ef41Sopenharmony_ci<table> 3591cb0ef41Sopenharmony_ci<tbody><tr><th>Version</th><th>Changes</th></tr> 3601cb0ef41Sopenharmony_ci<tr><td>v18.13.0</td> 3611cb0ef41Sopenharmony_ci<td><p>diagnostics_channel is now Stable.</p></td></tr> 3621cb0ef41Sopenharmony_ci<tr><td>v15.1.0, v14.17.0</td> 3631cb0ef41Sopenharmony_ci<td><p><span>Added in: v15.1.0, v14.17.0</span></p></td></tr> 3641cb0ef41Sopenharmony_ci</tbody></table> 3651cb0ef41Sopenharmony_ci</details> 3661cb0ef41Sopenharmony_ci</div> 3671cb0ef41Sopenharmony_ci 3681cb0ef41Sopenharmony_ci<p></p><div class="api_stability api_stability_2"><a href="documentation.html#stability-index">Stability: 2</a> - Stable</div><p></p> 3691cb0ef41Sopenharmony_ci<p><strong>Source Code:</strong> <a href="https://github.com/nodejs/node/blob/v18.20.1/lib/diagnostics_channel.js">lib/diagnostics_channel.js</a></p> 3701cb0ef41Sopenharmony_ci<p>The <code>node:diagnostics_channel</code> module provides an API to create named channels 3711cb0ef41Sopenharmony_cito report arbitrary message data for diagnostics purposes.</p> 3721cb0ef41Sopenharmony_ci<p>It can be accessed using:</p> 3731cb0ef41Sopenharmony_ci 3741cb0ef41Sopenharmony_ci<pre class="with-64-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> diagnostics_channel <span class="hljs-keyword">from</span> <span class="hljs-string">'node:diagnostics_channel'</span>;</code><code class="language-js cjs"><span class="hljs-keyword">const</span> diagnostics_channel = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:diagnostics_channel'</span>);</code><button class="copy-button">copy</button></pre> 3751cb0ef41Sopenharmony_ci<p>It is intended that a module writer wanting to report diagnostics messages 3761cb0ef41Sopenharmony_ciwill create one or many top-level channels to report messages through. 3771cb0ef41Sopenharmony_ciChannels may also be acquired at runtime but it is not encouraged 3781cb0ef41Sopenharmony_cidue to the additional overhead of doing so. Channels may be exported for 3791cb0ef41Sopenharmony_ciconvenience, but as long as the name is known it can be acquired anywhere.</p> 3801cb0ef41Sopenharmony_ci<p>If you intend for your module to produce diagnostics data for others to 3811cb0ef41Sopenharmony_ciconsume it is recommended that you include documentation of what named 3821cb0ef41Sopenharmony_cichannels are used along with the shape of the message data. Channel names 3831cb0ef41Sopenharmony_cishould generally include the module name to avoid collisions with data from 3841cb0ef41Sopenharmony_ciother modules.</p> 3851cb0ef41Sopenharmony_ci<section><h3>Public API<span><a class="mark" href="#public-api" id="public-api">#</a></span><a aria-hidden="true" class="legacy" id="diagnostics_channel_public_api"></a></h3> 3861cb0ef41Sopenharmony_ci<h4>Overview<span><a class="mark" href="#overview" id="overview">#</a></span><a aria-hidden="true" class="legacy" id="diagnostics_channel_overview"></a></h4> 3871cb0ef41Sopenharmony_ci<p>Following is a simple overview of the public API.</p> 3881cb0ef41Sopenharmony_ci 3891cb0ef41Sopenharmony_ci<pre class="with-64-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> diagnostics_channel <span class="hljs-keyword">from</span> <span class="hljs-string">'node:diagnostics_channel'</span>; 3901cb0ef41Sopenharmony_ci 3911cb0ef41Sopenharmony_ci<span class="hljs-comment">// Get a reusable channel object</span> 3921cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> channel = diagnostics_channel.<span class="hljs-title function_">channel</span>(<span class="hljs-string">'my-channel'</span>); 3931cb0ef41Sopenharmony_ci 3941cb0ef41Sopenharmony_ci<span class="hljs-keyword">function</span> <span class="hljs-title function_">onMessage</span>(<span class="hljs-params">message, name</span>) { 3951cb0ef41Sopenharmony_ci <span class="hljs-comment">// Received data</span> 3961cb0ef41Sopenharmony_ci} 3971cb0ef41Sopenharmony_ci 3981cb0ef41Sopenharmony_ci<span class="hljs-comment">// Subscribe to the channel</span> 3991cb0ef41Sopenharmony_cidiagnostics_channel.<span class="hljs-title function_">subscribe</span>(<span class="hljs-string">'my-channel'</span>, onMessage); 4001cb0ef41Sopenharmony_ci 4011cb0ef41Sopenharmony_ci<span class="hljs-comment">// Check if the channel has an active subscriber</span> 4021cb0ef41Sopenharmony_ci<span class="hljs-keyword">if</span> (channel.<span class="hljs-property">hasSubscribers</span>) { 4031cb0ef41Sopenharmony_ci <span class="hljs-comment">// Publish data to the channel</span> 4041cb0ef41Sopenharmony_ci channel.<span class="hljs-title function_">publish</span>({ 4051cb0ef41Sopenharmony_ci <span class="hljs-attr">some</span>: <span class="hljs-string">'data'</span>, 4061cb0ef41Sopenharmony_ci }); 4071cb0ef41Sopenharmony_ci} 4081cb0ef41Sopenharmony_ci 4091cb0ef41Sopenharmony_ci<span class="hljs-comment">// Unsubscribe from the channel</span> 4101cb0ef41Sopenharmony_cidiagnostics_channel.<span class="hljs-title function_">unsubscribe</span>(<span class="hljs-string">'my-channel'</span>, onMessage);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> diagnostics_channel = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:diagnostics_channel'</span>); 4111cb0ef41Sopenharmony_ci 4121cb0ef41Sopenharmony_ci<span class="hljs-comment">// Get a reusable channel object</span> 4131cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> channel = diagnostics_channel.<span class="hljs-title function_">channel</span>(<span class="hljs-string">'my-channel'</span>); 4141cb0ef41Sopenharmony_ci 4151cb0ef41Sopenharmony_ci<span class="hljs-keyword">function</span> <span class="hljs-title function_">onMessage</span>(<span class="hljs-params">message, name</span>) { 4161cb0ef41Sopenharmony_ci <span class="hljs-comment">// Received data</span> 4171cb0ef41Sopenharmony_ci} 4181cb0ef41Sopenharmony_ci 4191cb0ef41Sopenharmony_ci<span class="hljs-comment">// Subscribe to the channel</span> 4201cb0ef41Sopenharmony_cidiagnostics_channel.<span class="hljs-title function_">subscribe</span>(<span class="hljs-string">'my-channel'</span>, onMessage); 4211cb0ef41Sopenharmony_ci 4221cb0ef41Sopenharmony_ci<span class="hljs-comment">// Check if the channel has an active subscriber</span> 4231cb0ef41Sopenharmony_ci<span class="hljs-keyword">if</span> (channel.<span class="hljs-property">hasSubscribers</span>) { 4241cb0ef41Sopenharmony_ci <span class="hljs-comment">// Publish data to the channel</span> 4251cb0ef41Sopenharmony_ci channel.<span class="hljs-title function_">publish</span>({ 4261cb0ef41Sopenharmony_ci <span class="hljs-attr">some</span>: <span class="hljs-string">'data'</span>, 4271cb0ef41Sopenharmony_ci }); 4281cb0ef41Sopenharmony_ci} 4291cb0ef41Sopenharmony_ci 4301cb0ef41Sopenharmony_ci<span class="hljs-comment">// Unsubscribe from the channel</span> 4311cb0ef41Sopenharmony_cidiagnostics_channel.<span class="hljs-title function_">unsubscribe</span>(<span class="hljs-string">'my-channel'</span>, onMessage);</code><button class="copy-button">copy</button></pre> 4321cb0ef41Sopenharmony_ci<h5><code>diagnostics_channel.hasSubscribers(name)</code><span><a class="mark" href="#diagnostics_channelhassubscribersname" id="diagnostics_channelhassubscribersname">#</a></span><a aria-hidden="true" class="legacy" id="diagnostics_channel_diagnostics_channel_hassubscribers_name"></a></h5> 4331cb0ef41Sopenharmony_ci<div class="api_metadata"> 4341cb0ef41Sopenharmony_ci<span>Added in: v15.1.0, v14.17.0</span> 4351cb0ef41Sopenharmony_ci</div> 4361cb0ef41Sopenharmony_ci<ul> 4371cb0ef41Sopenharmony_ci<li><code>name</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Symbol_type" class="type"><symbol></a> The channel name</li> 4381cb0ef41Sopenharmony_ci<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> If there are active subscribers</li> 4391cb0ef41Sopenharmony_ci</ul> 4401cb0ef41Sopenharmony_ci<p>Check if there are active subscribers to the named channel. This is helpful if 4411cb0ef41Sopenharmony_cithe message you want to send might be expensive to prepare.</p> 4421cb0ef41Sopenharmony_ci<p>This API is optional but helpful when trying to publish messages from very 4431cb0ef41Sopenharmony_ciperformance-sensitive code.</p> 4441cb0ef41Sopenharmony_ci 4451cb0ef41Sopenharmony_ci<pre class="with-64-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> diagnostics_channel <span class="hljs-keyword">from</span> <span class="hljs-string">'node:diagnostics_channel'</span>; 4461cb0ef41Sopenharmony_ci 4471cb0ef41Sopenharmony_ci<span class="hljs-keyword">if</span> (diagnostics_channel.<span class="hljs-title function_">hasSubscribers</span>(<span class="hljs-string">'my-channel'</span>)) { 4481cb0ef41Sopenharmony_ci <span class="hljs-comment">// There are subscribers, prepare and publish message</span> 4491cb0ef41Sopenharmony_ci}</code><code class="language-js cjs"><span class="hljs-keyword">const</span> diagnostics_channel = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:diagnostics_channel'</span>); 4501cb0ef41Sopenharmony_ci 4511cb0ef41Sopenharmony_ci<span class="hljs-keyword">if</span> (diagnostics_channel.<span class="hljs-title function_">hasSubscribers</span>(<span class="hljs-string">'my-channel'</span>)) { 4521cb0ef41Sopenharmony_ci <span class="hljs-comment">// There are subscribers, prepare and publish message</span> 4531cb0ef41Sopenharmony_ci}</code><button class="copy-button">copy</button></pre> 4541cb0ef41Sopenharmony_ci<h5><code>diagnostics_channel.channel(name)</code><span><a class="mark" href="#diagnostics_channelchannelname" id="diagnostics_channelchannelname">#</a></span><a aria-hidden="true" class="legacy" id="diagnostics_channel_diagnostics_channel_channel_name"></a></h5> 4551cb0ef41Sopenharmony_ci<div class="api_metadata"> 4561cb0ef41Sopenharmony_ci<span>Added in: v15.1.0, v14.17.0</span> 4571cb0ef41Sopenharmony_ci</div> 4581cb0ef41Sopenharmony_ci<ul> 4591cb0ef41Sopenharmony_ci<li><code>name</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Symbol_type" class="type"><symbol></a> The channel name</li> 4601cb0ef41Sopenharmony_ci<li>Returns: <a href="diagnostics_channel.html#class-channel" class="type"><Channel></a> The named channel object</li> 4611cb0ef41Sopenharmony_ci</ul> 4621cb0ef41Sopenharmony_ci<p>This is the primary entry-point for anyone wanting to publish to a named 4631cb0ef41Sopenharmony_cichannel. It produces a channel object which is optimized to reduce overhead at 4641cb0ef41Sopenharmony_cipublish time as much as possible.</p> 4651cb0ef41Sopenharmony_ci 4661cb0ef41Sopenharmony_ci<pre class="with-64-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> diagnostics_channel <span class="hljs-keyword">from</span> <span class="hljs-string">'node:diagnostics_channel'</span>; 4671cb0ef41Sopenharmony_ci 4681cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> channel = diagnostics_channel.<span class="hljs-title function_">channel</span>(<span class="hljs-string">'my-channel'</span>);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> diagnostics_channel = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:diagnostics_channel'</span>); 4691cb0ef41Sopenharmony_ci 4701cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> channel = diagnostics_channel.<span class="hljs-title function_">channel</span>(<span class="hljs-string">'my-channel'</span>);</code><button class="copy-button">copy</button></pre> 4711cb0ef41Sopenharmony_ci<h5><code>diagnostics_channel.subscribe(name, onMessage)</code><span><a class="mark" href="#diagnostics_channelsubscribename-onmessage" id="diagnostics_channelsubscribename-onmessage">#</a></span><a aria-hidden="true" class="legacy" id="diagnostics_channel_diagnostics_channel_subscribe_name_onmessage"></a></h5> 4721cb0ef41Sopenharmony_ci<div class="api_metadata"> 4731cb0ef41Sopenharmony_ci<span>Added in: v18.7.0</span> 4741cb0ef41Sopenharmony_ci</div> 4751cb0ef41Sopenharmony_ci<ul> 4761cb0ef41Sopenharmony_ci<li><code>name</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Symbol_type" class="type"><symbol></a> The channel name</li> 4771cb0ef41Sopenharmony_ci<li><code>onMessage</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> The handler to receive channel messages 4781cb0ef41Sopenharmony_ci<ul> 4791cb0ef41Sopenharmony_ci<li><code>message</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a> The message data</li> 4801cb0ef41Sopenharmony_ci<li><code>name</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Symbol_type" class="type"><symbol></a> The name of the channel</li> 4811cb0ef41Sopenharmony_ci</ul> 4821cb0ef41Sopenharmony_ci</li> 4831cb0ef41Sopenharmony_ci</ul> 4841cb0ef41Sopenharmony_ci<p>Register a message handler to subscribe to this channel. This message handler 4851cb0ef41Sopenharmony_ciwill be run synchronously whenever a message is published to the channel. Any 4861cb0ef41Sopenharmony_cierrors thrown in the message handler will trigger an <a href="process.html#event-uncaughtexception"><code>'uncaughtException'</code></a>.</p> 4871cb0ef41Sopenharmony_ci 4881cb0ef41Sopenharmony_ci<pre class="with-64-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> diagnostics_channel <span class="hljs-keyword">from</span> <span class="hljs-string">'node:diagnostics_channel'</span>; 4891cb0ef41Sopenharmony_ci 4901cb0ef41Sopenharmony_cidiagnostics_channel.<span class="hljs-title function_">subscribe</span>(<span class="hljs-string">'my-channel'</span>, <span class="hljs-function">(<span class="hljs-params">message, name</span>) =></span> { 4911cb0ef41Sopenharmony_ci <span class="hljs-comment">// Received data</span> 4921cb0ef41Sopenharmony_ci});</code><code class="language-js cjs"><span class="hljs-keyword">const</span> diagnostics_channel = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:diagnostics_channel'</span>); 4931cb0ef41Sopenharmony_ci 4941cb0ef41Sopenharmony_cidiagnostics_channel.<span class="hljs-title function_">subscribe</span>(<span class="hljs-string">'my-channel'</span>, <span class="hljs-function">(<span class="hljs-params">message, name</span>) =></span> { 4951cb0ef41Sopenharmony_ci <span class="hljs-comment">// Received data</span> 4961cb0ef41Sopenharmony_ci});</code><button class="copy-button">copy</button></pre> 4971cb0ef41Sopenharmony_ci<h5><code>diagnostics_channel.unsubscribe(name, onMessage)</code><span><a class="mark" href="#diagnostics_channelunsubscribename-onmessage" id="diagnostics_channelunsubscribename-onmessage">#</a></span><a aria-hidden="true" class="legacy" id="diagnostics_channel_diagnostics_channel_unsubscribe_name_onmessage"></a></h5> 4981cb0ef41Sopenharmony_ci<div class="api_metadata"> 4991cb0ef41Sopenharmony_ci<span>Added in: v18.7.0</span> 5001cb0ef41Sopenharmony_ci</div> 5011cb0ef41Sopenharmony_ci<ul> 5021cb0ef41Sopenharmony_ci<li><code>name</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Symbol_type" class="type"><symbol></a> The channel name</li> 5031cb0ef41Sopenharmony_ci<li><code>onMessage</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> The previous subscribed handler to remove</li> 5041cb0ef41Sopenharmony_ci<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> <code>true</code> if the handler was found, <code>false</code> otherwise.</li> 5051cb0ef41Sopenharmony_ci</ul> 5061cb0ef41Sopenharmony_ci<p>Remove a message handler previously registered to this channel with 5071cb0ef41Sopenharmony_ci<a href="#diagnostics_channelsubscribename-onmessage"><code>diagnostics_channel.subscribe(name, onMessage)</code></a>.</p> 5081cb0ef41Sopenharmony_ci 5091cb0ef41Sopenharmony_ci<pre class="with-64-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> diagnostics_channel <span class="hljs-keyword">from</span> <span class="hljs-string">'node:diagnostics_channel'</span>; 5101cb0ef41Sopenharmony_ci 5111cb0ef41Sopenharmony_ci<span class="hljs-keyword">function</span> <span class="hljs-title function_">onMessage</span>(<span class="hljs-params">message, name</span>) { 5121cb0ef41Sopenharmony_ci <span class="hljs-comment">// Received data</span> 5131cb0ef41Sopenharmony_ci} 5141cb0ef41Sopenharmony_ci 5151cb0ef41Sopenharmony_cidiagnostics_channel.<span class="hljs-title function_">subscribe</span>(<span class="hljs-string">'my-channel'</span>, onMessage); 5161cb0ef41Sopenharmony_ci 5171cb0ef41Sopenharmony_cidiagnostics_channel.<span class="hljs-title function_">unsubscribe</span>(<span class="hljs-string">'my-channel'</span>, onMessage);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> diagnostics_channel = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:diagnostics_channel'</span>); 5181cb0ef41Sopenharmony_ci 5191cb0ef41Sopenharmony_ci<span class="hljs-keyword">function</span> <span class="hljs-title function_">onMessage</span>(<span class="hljs-params">message, name</span>) { 5201cb0ef41Sopenharmony_ci <span class="hljs-comment">// Received data</span> 5211cb0ef41Sopenharmony_ci} 5221cb0ef41Sopenharmony_ci 5231cb0ef41Sopenharmony_cidiagnostics_channel.<span class="hljs-title function_">subscribe</span>(<span class="hljs-string">'my-channel'</span>, onMessage); 5241cb0ef41Sopenharmony_ci 5251cb0ef41Sopenharmony_cidiagnostics_channel.<span class="hljs-title function_">unsubscribe</span>(<span class="hljs-string">'my-channel'</span>, onMessage);</code><button class="copy-button">copy</button></pre> 5261cb0ef41Sopenharmony_ci<h5><code>diagnostics_channel.tracingChannel(nameOrChannels)</code><span><a class="mark" href="#diagnostics_channeltracingchannelnameorchannels" id="diagnostics_channeltracingchannelnameorchannels">#</a></span><a aria-hidden="true" class="legacy" id="diagnostics_channel_diagnostics_channel_tracingchannel_nameorchannels"></a></h5> 5271cb0ef41Sopenharmony_ci<div class="api_metadata"> 5281cb0ef41Sopenharmony_ci<span>Added in: v18.19.0</span> 5291cb0ef41Sopenharmony_ci</div> 5301cb0ef41Sopenharmony_ci<p></p><div class="api_stability api_stability_1"><a href="documentation.html#stability-index">Stability: 1</a> - Experimental</div><p></p> 5311cb0ef41Sopenharmony_ci<ul> 5321cb0ef41Sopenharmony_ci<li><code>nameOrChannels</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="diagnostics_channel.html#class-tracingchannel" class="type"><TracingChannel></a> Channel name or 5331cb0ef41Sopenharmony_ciobject containing all the <a href="#tracingchannel-channels">TracingChannel Channels</a></li> 5341cb0ef41Sopenharmony_ci<li>Returns: <a href="diagnostics_channel.html#class-tracingchannel" class="type"><TracingChannel></a> Collection of channels to trace with</li> 5351cb0ef41Sopenharmony_ci</ul> 5361cb0ef41Sopenharmony_ci<p>Creates a <a href="#class-tracingchannel"><code>TracingChannel</code></a> wrapper for the given 5371cb0ef41Sopenharmony_ci<a href="#tracingchannel-channels">TracingChannel Channels</a>. If a name is given, the corresponding tracing 5381cb0ef41Sopenharmony_cichannels will be created in the form of <code>tracing:${name}:${eventType}</code> where 5391cb0ef41Sopenharmony_ci<code>eventType</code> corresponds to the types of <a href="#tracingchannel-channels">TracingChannel Channels</a>.</p> 5401cb0ef41Sopenharmony_ci 5411cb0ef41Sopenharmony_ci<pre class="with-64-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> diagnostics_channel <span class="hljs-keyword">from</span> <span class="hljs-string">'node:diagnostics_channel'</span>; 5421cb0ef41Sopenharmony_ci 5431cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> channelsByName = diagnostics_channel.<span class="hljs-title function_">tracingChannel</span>(<span class="hljs-string">'my-channel'</span>); 5441cb0ef41Sopenharmony_ci 5451cb0ef41Sopenharmony_ci<span class="hljs-comment">// or...</span> 5461cb0ef41Sopenharmony_ci 5471cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> channelsByCollection = diagnostics_channel.<span class="hljs-title function_">tracingChannel</span>({ 5481cb0ef41Sopenharmony_ci <span class="hljs-attr">start</span>: diagnostics_channel.<span class="hljs-title function_">channel</span>(<span class="hljs-string">'tracing:my-channel:start'</span>), 5491cb0ef41Sopenharmony_ci <span class="hljs-attr">end</span>: diagnostics_channel.<span class="hljs-title function_">channel</span>(<span class="hljs-string">'tracing:my-channel:end'</span>), 5501cb0ef41Sopenharmony_ci <span class="hljs-attr">asyncStart</span>: diagnostics_channel.<span class="hljs-title function_">channel</span>(<span class="hljs-string">'tracing:my-channel:asyncStart'</span>), 5511cb0ef41Sopenharmony_ci <span class="hljs-attr">asyncEnd</span>: diagnostics_channel.<span class="hljs-title function_">channel</span>(<span class="hljs-string">'tracing:my-channel:asyncEnd'</span>), 5521cb0ef41Sopenharmony_ci <span class="hljs-attr">error</span>: diagnostics_channel.<span class="hljs-title function_">channel</span>(<span class="hljs-string">'tracing:my-channel:error'</span>), 5531cb0ef41Sopenharmony_ci});</code><code class="language-js cjs"><span class="hljs-keyword">const</span> diagnostics_channel = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:diagnostics_channel'</span>); 5541cb0ef41Sopenharmony_ci 5551cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> channelsByName = diagnostics_channel.<span class="hljs-title function_">tracingChannel</span>(<span class="hljs-string">'my-channel'</span>); 5561cb0ef41Sopenharmony_ci 5571cb0ef41Sopenharmony_ci<span class="hljs-comment">// or...</span> 5581cb0ef41Sopenharmony_ci 5591cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> channelsByCollection = diagnostics_channel.<span class="hljs-title function_">tracingChannel</span>({ 5601cb0ef41Sopenharmony_ci <span class="hljs-attr">start</span>: diagnostics_channel.<span class="hljs-title function_">channel</span>(<span class="hljs-string">'tracing:my-channel:start'</span>), 5611cb0ef41Sopenharmony_ci <span class="hljs-attr">end</span>: diagnostics_channel.<span class="hljs-title function_">channel</span>(<span class="hljs-string">'tracing:my-channel:end'</span>), 5621cb0ef41Sopenharmony_ci <span class="hljs-attr">asyncStart</span>: diagnostics_channel.<span class="hljs-title function_">channel</span>(<span class="hljs-string">'tracing:my-channel:asyncStart'</span>), 5631cb0ef41Sopenharmony_ci <span class="hljs-attr">asyncEnd</span>: diagnostics_channel.<span class="hljs-title function_">channel</span>(<span class="hljs-string">'tracing:my-channel:asyncEnd'</span>), 5641cb0ef41Sopenharmony_ci <span class="hljs-attr">error</span>: diagnostics_channel.<span class="hljs-title function_">channel</span>(<span class="hljs-string">'tracing:my-channel:error'</span>), 5651cb0ef41Sopenharmony_ci});</code><button class="copy-button">copy</button></pre> 5661cb0ef41Sopenharmony_ci<h4>Class: <code>Channel</code><span><a class="mark" href="#class-channel" id="class-channel">#</a></span><a aria-hidden="true" class="legacy" id="diagnostics_channel_class_channel"></a></h4> 5671cb0ef41Sopenharmony_ci<div class="api_metadata"> 5681cb0ef41Sopenharmony_ci<span>Added in: v15.1.0, v14.17.0</span> 5691cb0ef41Sopenharmony_ci</div> 5701cb0ef41Sopenharmony_ci<p>The class <code>Channel</code> represents an individual named channel within the data 5711cb0ef41Sopenharmony_cipipeline. It is used to track subscribers and to publish messages when there 5721cb0ef41Sopenharmony_ciare subscribers present. It exists as a separate object to avoid channel 5731cb0ef41Sopenharmony_cilookups at publish time, enabling very fast publish speeds and allowing 5741cb0ef41Sopenharmony_cifor heavy use while incurring very minimal cost. Channels are created with 5751cb0ef41Sopenharmony_ci<a href="#diagnostics_channelchannelname"><code>diagnostics_channel.channel(name)</code></a>, constructing a channel directly 5761cb0ef41Sopenharmony_ciwith <code>new Channel(name)</code> is not supported.</p> 5771cb0ef41Sopenharmony_ci<h5><code>channel.hasSubscribers</code><span><a class="mark" href="#channelhassubscribers" id="channelhassubscribers">#</a></span><a aria-hidden="true" class="legacy" id="diagnostics_channel_channel_hassubscribers"></a></h5> 5781cb0ef41Sopenharmony_ci<div class="api_metadata"> 5791cb0ef41Sopenharmony_ci<span>Added in: v15.1.0, v14.17.0</span> 5801cb0ef41Sopenharmony_ci</div> 5811cb0ef41Sopenharmony_ci<ul> 5821cb0ef41Sopenharmony_ci<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> If there are active subscribers</li> 5831cb0ef41Sopenharmony_ci</ul> 5841cb0ef41Sopenharmony_ci<p>Check if there are active subscribers to this channel. This is helpful if 5851cb0ef41Sopenharmony_cithe message you want to send might be expensive to prepare.</p> 5861cb0ef41Sopenharmony_ci<p>This API is optional but helpful when trying to publish messages from very 5871cb0ef41Sopenharmony_ciperformance-sensitive code.</p> 5881cb0ef41Sopenharmony_ci 5891cb0ef41Sopenharmony_ci<pre class="with-64-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> diagnostics_channel <span class="hljs-keyword">from</span> <span class="hljs-string">'node:diagnostics_channel'</span>; 5901cb0ef41Sopenharmony_ci 5911cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> channel = diagnostics_channel.<span class="hljs-title function_">channel</span>(<span class="hljs-string">'my-channel'</span>); 5921cb0ef41Sopenharmony_ci 5931cb0ef41Sopenharmony_ci<span class="hljs-keyword">if</span> (channel.<span class="hljs-property">hasSubscribers</span>) { 5941cb0ef41Sopenharmony_ci <span class="hljs-comment">// There are subscribers, prepare and publish message</span> 5951cb0ef41Sopenharmony_ci}</code><code class="language-js cjs"><span class="hljs-keyword">const</span> diagnostics_channel = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:diagnostics_channel'</span>); 5961cb0ef41Sopenharmony_ci 5971cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> channel = diagnostics_channel.<span class="hljs-title function_">channel</span>(<span class="hljs-string">'my-channel'</span>); 5981cb0ef41Sopenharmony_ci 5991cb0ef41Sopenharmony_ci<span class="hljs-keyword">if</span> (channel.<span class="hljs-property">hasSubscribers</span>) { 6001cb0ef41Sopenharmony_ci <span class="hljs-comment">// There are subscribers, prepare and publish message</span> 6011cb0ef41Sopenharmony_ci}</code><button class="copy-button">copy</button></pre> 6021cb0ef41Sopenharmony_ci<h5><code>channel.publish(message)</code><span><a class="mark" href="#channelpublishmessage" id="channelpublishmessage">#</a></span><a aria-hidden="true" class="legacy" id="diagnostics_channel_channel_publish_message"></a></h5> 6031cb0ef41Sopenharmony_ci<div class="api_metadata"> 6041cb0ef41Sopenharmony_ci<span>Added in: v15.1.0, v14.17.0</span> 6051cb0ef41Sopenharmony_ci</div> 6061cb0ef41Sopenharmony_ci<ul> 6071cb0ef41Sopenharmony_ci<li><code>message</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a> The message to send to the channel subscribers</li> 6081cb0ef41Sopenharmony_ci</ul> 6091cb0ef41Sopenharmony_ci<p>Publish a message to any subscribers to the channel. This will trigger 6101cb0ef41Sopenharmony_cimessage handlers synchronously so they will execute within the same context.</p> 6111cb0ef41Sopenharmony_ci 6121cb0ef41Sopenharmony_ci<pre class="with-64-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> diagnostics_channel <span class="hljs-keyword">from</span> <span class="hljs-string">'node:diagnostics_channel'</span>; 6131cb0ef41Sopenharmony_ci 6141cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> channel = diagnostics_channel.<span class="hljs-title function_">channel</span>(<span class="hljs-string">'my-channel'</span>); 6151cb0ef41Sopenharmony_ci 6161cb0ef41Sopenharmony_cichannel.<span class="hljs-title function_">publish</span>({ 6171cb0ef41Sopenharmony_ci <span class="hljs-attr">some</span>: <span class="hljs-string">'message'</span>, 6181cb0ef41Sopenharmony_ci});</code><code class="language-js cjs"><span class="hljs-keyword">const</span> diagnostics_channel = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:diagnostics_channel'</span>); 6191cb0ef41Sopenharmony_ci 6201cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> channel = diagnostics_channel.<span class="hljs-title function_">channel</span>(<span class="hljs-string">'my-channel'</span>); 6211cb0ef41Sopenharmony_ci 6221cb0ef41Sopenharmony_cichannel.<span class="hljs-title function_">publish</span>({ 6231cb0ef41Sopenharmony_ci <span class="hljs-attr">some</span>: <span class="hljs-string">'message'</span>, 6241cb0ef41Sopenharmony_ci});</code><button class="copy-button">copy</button></pre> 6251cb0ef41Sopenharmony_ci<h5><code>channel.subscribe(onMessage)</code><span><a class="mark" href="#channelsubscribeonmessage" id="channelsubscribeonmessage">#</a></span><a aria-hidden="true" class="legacy" id="diagnostics_channel_channel_subscribe_onmessage"></a></h5> 6261cb0ef41Sopenharmony_ci<div class="api_metadata"> 6271cb0ef41Sopenharmony_ci<span>Added in: v15.1.0, v14.17.0</span><span>Deprecated since: v18.7.0</span> 6281cb0ef41Sopenharmony_ci</div> 6291cb0ef41Sopenharmony_ci<p></p><div class="api_stability api_stability_0"><a href="documentation.html#stability-index">Stability: 0</a> - Deprecated: Use <a href="#diagnostics_channelsubscribename-onmessage"><code>diagnostics_channel.subscribe(name, onMessage)</code></a></div><p></p> 6301cb0ef41Sopenharmony_ci<ul> 6311cb0ef41Sopenharmony_ci<li><code>onMessage</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> The handler to receive channel messages 6321cb0ef41Sopenharmony_ci<ul> 6331cb0ef41Sopenharmony_ci<li><code>message</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a> The message data</li> 6341cb0ef41Sopenharmony_ci<li><code>name</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Symbol_type" class="type"><symbol></a> The name of the channel</li> 6351cb0ef41Sopenharmony_ci</ul> 6361cb0ef41Sopenharmony_ci</li> 6371cb0ef41Sopenharmony_ci</ul> 6381cb0ef41Sopenharmony_ci<p>Register a message handler to subscribe to this channel. This message handler 6391cb0ef41Sopenharmony_ciwill be run synchronously whenever a message is published to the channel. Any 6401cb0ef41Sopenharmony_cierrors thrown in the message handler will trigger an <a href="process.html#event-uncaughtexception"><code>'uncaughtException'</code></a>.</p> 6411cb0ef41Sopenharmony_ci 6421cb0ef41Sopenharmony_ci<pre class="with-64-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> diagnostics_channel <span class="hljs-keyword">from</span> <span class="hljs-string">'node:diagnostics_channel'</span>; 6431cb0ef41Sopenharmony_ci 6441cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> channel = diagnostics_channel.<span class="hljs-title function_">channel</span>(<span class="hljs-string">'my-channel'</span>); 6451cb0ef41Sopenharmony_ci 6461cb0ef41Sopenharmony_cichannel.<span class="hljs-title function_">subscribe</span>(<span class="hljs-function">(<span class="hljs-params">message, name</span>) =></span> { 6471cb0ef41Sopenharmony_ci <span class="hljs-comment">// Received data</span> 6481cb0ef41Sopenharmony_ci});</code><code class="language-js cjs"><span class="hljs-keyword">const</span> diagnostics_channel = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:diagnostics_channel'</span>); 6491cb0ef41Sopenharmony_ci 6501cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> channel = diagnostics_channel.<span class="hljs-title function_">channel</span>(<span class="hljs-string">'my-channel'</span>); 6511cb0ef41Sopenharmony_ci 6521cb0ef41Sopenharmony_cichannel.<span class="hljs-title function_">subscribe</span>(<span class="hljs-function">(<span class="hljs-params">message, name</span>) =></span> { 6531cb0ef41Sopenharmony_ci <span class="hljs-comment">// Received data</span> 6541cb0ef41Sopenharmony_ci});</code><button class="copy-button">copy</button></pre> 6551cb0ef41Sopenharmony_ci<h5><code>channel.unsubscribe(onMessage)</code><span><a class="mark" href="#channelunsubscribeonmessage" id="channelunsubscribeonmessage">#</a></span><a aria-hidden="true" class="legacy" id="diagnostics_channel_channel_unsubscribe_onmessage"></a></h5> 6561cb0ef41Sopenharmony_ci<div class="api_metadata"> 6571cb0ef41Sopenharmony_ci<details class="changelog"><summary>History</summary> 6581cb0ef41Sopenharmony_ci<table> 6591cb0ef41Sopenharmony_ci<tbody><tr><th>Version</th><th>Changes</th></tr> 6601cb0ef41Sopenharmony_ci<tr><td>v18.7.0</td> 6611cb0ef41Sopenharmony_ci<td><p><span>Deprecated since: v18.7.0</span></p></td></tr> 6621cb0ef41Sopenharmony_ci<tr><td>v17.1.0, v16.14.0, v14.19.0</td> 6631cb0ef41Sopenharmony_ci<td><p>Added return value. Added to channels without subscribers.</p></td></tr> 6641cb0ef41Sopenharmony_ci<tr><td>v15.1.0, v14.17.0</td> 6651cb0ef41Sopenharmony_ci<td><p><span>Added in: v15.1.0, v14.17.0</span></p></td></tr> 6661cb0ef41Sopenharmony_ci</tbody></table> 6671cb0ef41Sopenharmony_ci</details> 6681cb0ef41Sopenharmony_ci</div> 6691cb0ef41Sopenharmony_ci<p></p><div class="api_stability api_stability_0"><a href="documentation.html#stability-index">Stability: 0</a> - Deprecated: Use <a href="#diagnostics_channelunsubscribename-onmessage"><code>diagnostics_channel.unsubscribe(name, onMessage)</code></a></div><p></p> 6701cb0ef41Sopenharmony_ci<ul> 6711cb0ef41Sopenharmony_ci<li><code>onMessage</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> The previous subscribed handler to remove</li> 6721cb0ef41Sopenharmony_ci<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> <code>true</code> if the handler was found, <code>false</code> otherwise.</li> 6731cb0ef41Sopenharmony_ci</ul> 6741cb0ef41Sopenharmony_ci<p>Remove a message handler previously registered to this channel with 6751cb0ef41Sopenharmony_ci<a href="#channelsubscribeonmessage"><code>channel.subscribe(onMessage)</code></a>.</p> 6761cb0ef41Sopenharmony_ci 6771cb0ef41Sopenharmony_ci<pre class="with-64-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> diagnostics_channel <span class="hljs-keyword">from</span> <span class="hljs-string">'node:diagnostics_channel'</span>; 6781cb0ef41Sopenharmony_ci 6791cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> channel = diagnostics_channel.<span class="hljs-title function_">channel</span>(<span class="hljs-string">'my-channel'</span>); 6801cb0ef41Sopenharmony_ci 6811cb0ef41Sopenharmony_ci<span class="hljs-keyword">function</span> <span class="hljs-title function_">onMessage</span>(<span class="hljs-params">message, name</span>) { 6821cb0ef41Sopenharmony_ci <span class="hljs-comment">// Received data</span> 6831cb0ef41Sopenharmony_ci} 6841cb0ef41Sopenharmony_ci 6851cb0ef41Sopenharmony_cichannel.<span class="hljs-title function_">subscribe</span>(onMessage); 6861cb0ef41Sopenharmony_ci 6871cb0ef41Sopenharmony_cichannel.<span class="hljs-title function_">unsubscribe</span>(onMessage);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> diagnostics_channel = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:diagnostics_channel'</span>); 6881cb0ef41Sopenharmony_ci 6891cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> channel = diagnostics_channel.<span class="hljs-title function_">channel</span>(<span class="hljs-string">'my-channel'</span>); 6901cb0ef41Sopenharmony_ci 6911cb0ef41Sopenharmony_ci<span class="hljs-keyword">function</span> <span class="hljs-title function_">onMessage</span>(<span class="hljs-params">message, name</span>) { 6921cb0ef41Sopenharmony_ci <span class="hljs-comment">// Received data</span> 6931cb0ef41Sopenharmony_ci} 6941cb0ef41Sopenharmony_ci 6951cb0ef41Sopenharmony_cichannel.<span class="hljs-title function_">subscribe</span>(onMessage); 6961cb0ef41Sopenharmony_ci 6971cb0ef41Sopenharmony_cichannel.<span class="hljs-title function_">unsubscribe</span>(onMessage);</code><button class="copy-button">copy</button></pre> 6981cb0ef41Sopenharmony_ci<h5><code>channel.bindStore(store[, transform])</code><span><a class="mark" href="#channelbindstorestore-transform" id="channelbindstorestore-transform">#</a></span><a aria-hidden="true" class="legacy" id="diagnostics_channel_channel_bindstore_store_transform"></a></h5> 6991cb0ef41Sopenharmony_ci<div class="api_metadata"> 7001cb0ef41Sopenharmony_ci<span>Added in: v18.19.0</span> 7011cb0ef41Sopenharmony_ci</div> 7021cb0ef41Sopenharmony_ci<p></p><div class="api_stability api_stability_1"><a href="documentation.html#stability-index">Stability: 1</a> - Experimental</div><p></p> 7031cb0ef41Sopenharmony_ci<ul> 7041cb0ef41Sopenharmony_ci<li><code>store</code> <a href="async_context.html#class-asynclocalstorage" class="type"><AsyncLocalStorage></a> The store to which to bind the context data</li> 7051cb0ef41Sopenharmony_ci<li><code>transform</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> Transform context data before setting the store context</li> 7061cb0ef41Sopenharmony_ci</ul> 7071cb0ef41Sopenharmony_ci<p>When <a href="#channelrunstorescontext-fn-thisarg-args"><code>channel.runStores(context, ...)</code></a> is called, the given context data 7081cb0ef41Sopenharmony_ciwill be applied to any store bound to the channel. If the store has already been 7091cb0ef41Sopenharmony_cibound the previous <code>transform</code> function will be replaced with the new one. 7101cb0ef41Sopenharmony_ciThe <code>transform</code> function may be omitted to set the given context data as the 7111cb0ef41Sopenharmony_cicontext directly.</p> 7121cb0ef41Sopenharmony_ci 7131cb0ef41Sopenharmony_ci<pre class="with-64-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> diagnostics_channel <span class="hljs-keyword">from</span> <span class="hljs-string">'node:diagnostics_channel'</span>; 7141cb0ef41Sopenharmony_ci<span class="hljs-keyword">import</span> { <span class="hljs-title class_">AsyncLocalStorage</span> } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:async_hooks'</span>; 7151cb0ef41Sopenharmony_ci 7161cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> store = <span class="hljs-keyword">new</span> <span class="hljs-title class_">AsyncLocalStorage</span>(); 7171cb0ef41Sopenharmony_ci 7181cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> channel = diagnostics_channel.<span class="hljs-title function_">channel</span>(<span class="hljs-string">'my-channel'</span>); 7191cb0ef41Sopenharmony_ci 7201cb0ef41Sopenharmony_cichannel.<span class="hljs-title function_">bindStore</span>(store, <span class="hljs-function">(<span class="hljs-params">data</span>) =></span> { 7211cb0ef41Sopenharmony_ci <span class="hljs-keyword">return</span> { data }; 7221cb0ef41Sopenharmony_ci});</code><code class="language-js cjs"><span class="hljs-keyword">const</span> diagnostics_channel = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:diagnostics_channel'</span>); 7231cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> { <span class="hljs-title class_">AsyncLocalStorage</span> } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:async_hooks'</span>); 7241cb0ef41Sopenharmony_ci 7251cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> store = <span class="hljs-keyword">new</span> <span class="hljs-title class_">AsyncLocalStorage</span>(); 7261cb0ef41Sopenharmony_ci 7271cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> channel = diagnostics_channel.<span class="hljs-title function_">channel</span>(<span class="hljs-string">'my-channel'</span>); 7281cb0ef41Sopenharmony_ci 7291cb0ef41Sopenharmony_cichannel.<span class="hljs-title function_">bindStore</span>(store, <span class="hljs-function">(<span class="hljs-params">data</span>) =></span> { 7301cb0ef41Sopenharmony_ci <span class="hljs-keyword">return</span> { data }; 7311cb0ef41Sopenharmony_ci});</code><button class="copy-button">copy</button></pre> 7321cb0ef41Sopenharmony_ci<h5><code>channel.unbindStore(store)</code><span><a class="mark" href="#channelunbindstorestore" id="channelunbindstorestore">#</a></span><a aria-hidden="true" class="legacy" id="diagnostics_channel_channel_unbindstore_store"></a></h5> 7331cb0ef41Sopenharmony_ci<div class="api_metadata"> 7341cb0ef41Sopenharmony_ci<span>Added in: v18.19.0</span> 7351cb0ef41Sopenharmony_ci</div> 7361cb0ef41Sopenharmony_ci<p></p><div class="api_stability api_stability_1"><a href="documentation.html#stability-index">Stability: 1</a> - Experimental</div><p></p> 7371cb0ef41Sopenharmony_ci<ul> 7381cb0ef41Sopenharmony_ci<li><code>store</code> <a href="async_context.html#class-asynclocalstorage" class="type"><AsyncLocalStorage></a> The store to unbind from the channel.</li> 7391cb0ef41Sopenharmony_ci<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> <code>true</code> if the store was found, <code>false</code> otherwise.</li> 7401cb0ef41Sopenharmony_ci</ul> 7411cb0ef41Sopenharmony_ci<p>Remove a message handler previously registered to this channel with 7421cb0ef41Sopenharmony_ci<a href="#channelbindstorestore-transform"><code>channel.bindStore(store)</code></a>.</p> 7431cb0ef41Sopenharmony_ci 7441cb0ef41Sopenharmony_ci<pre class="with-64-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> diagnostics_channel <span class="hljs-keyword">from</span> <span class="hljs-string">'node:diagnostics_channel'</span>; 7451cb0ef41Sopenharmony_ci<span class="hljs-keyword">import</span> { <span class="hljs-title class_">AsyncLocalStorage</span> } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:async_hooks'</span>; 7461cb0ef41Sopenharmony_ci 7471cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> store = <span class="hljs-keyword">new</span> <span class="hljs-title class_">AsyncLocalStorage</span>(); 7481cb0ef41Sopenharmony_ci 7491cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> channel = diagnostics_channel.<span class="hljs-title function_">channel</span>(<span class="hljs-string">'my-channel'</span>); 7501cb0ef41Sopenharmony_ci 7511cb0ef41Sopenharmony_cichannel.<span class="hljs-title function_">bindStore</span>(store); 7521cb0ef41Sopenharmony_cichannel.<span class="hljs-title function_">unbindStore</span>(store);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> diagnostics_channel = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:diagnostics_channel'</span>); 7531cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> { <span class="hljs-title class_">AsyncLocalStorage</span> } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:async_hooks'</span>); 7541cb0ef41Sopenharmony_ci 7551cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> store = <span class="hljs-keyword">new</span> <span class="hljs-title class_">AsyncLocalStorage</span>(); 7561cb0ef41Sopenharmony_ci 7571cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> channel = diagnostics_channel.<span class="hljs-title function_">channel</span>(<span class="hljs-string">'my-channel'</span>); 7581cb0ef41Sopenharmony_ci 7591cb0ef41Sopenharmony_cichannel.<span class="hljs-title function_">bindStore</span>(store); 7601cb0ef41Sopenharmony_cichannel.<span class="hljs-title function_">unbindStore</span>(store);</code><button class="copy-button">copy</button></pre> 7611cb0ef41Sopenharmony_ci<h5><code>channel.runStores(context, fn[, thisArg[, ...args]])</code><span><a class="mark" href="#channelrunstorescontext-fn-thisarg-args" id="channelrunstorescontext-fn-thisarg-args">#</a></span><a aria-hidden="true" class="legacy" id="diagnostics_channel_channel_runstores_context_fn_thisarg_args"></a></h5> 7621cb0ef41Sopenharmony_ci<div class="api_metadata"> 7631cb0ef41Sopenharmony_ci<span>Added in: v18.19.0</span> 7641cb0ef41Sopenharmony_ci</div> 7651cb0ef41Sopenharmony_ci<p></p><div class="api_stability api_stability_1"><a href="documentation.html#stability-index">Stability: 1</a> - Experimental</div><p></p> 7661cb0ef41Sopenharmony_ci<ul> 7671cb0ef41Sopenharmony_ci<li><code>context</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a> Message to send to subscribers and bind to stores</li> 7681cb0ef41Sopenharmony_ci<li><code>fn</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> Handler to run within the entered storage context</li> 7691cb0ef41Sopenharmony_ci<li><code>thisArg</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a> The receiver to be used for the function call.</li> 7701cb0ef41Sopenharmony_ci<li><code>...args</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a> Optional arguments to pass to the function.</li> 7711cb0ef41Sopenharmony_ci</ul> 7721cb0ef41Sopenharmony_ci<p>Applies the given data to any AsyncLocalStorage instances bound to the channel 7731cb0ef41Sopenharmony_cifor the duration of the given function, then publishes to the channel within 7741cb0ef41Sopenharmony_cithe scope of that data is applied to the stores.</p> 7751cb0ef41Sopenharmony_ci<p>If a transform function was given to <a href="#channelbindstorestore-transform"><code>channel.bindStore(store)</code></a> it will be 7761cb0ef41Sopenharmony_ciapplied to transform the message data before it becomes the context value for 7771cb0ef41Sopenharmony_cithe store. The prior storage context is accessible from within the transform 7781cb0ef41Sopenharmony_cifunction in cases where context linking is required.</p> 7791cb0ef41Sopenharmony_ci<p>The context applied to the store should be accesible in any async code which 7801cb0ef41Sopenharmony_cicontinues from execution which began during the given function, however 7811cb0ef41Sopenharmony_cithere are some situations in which <a href="async_context.html#troubleshooting-context-loss">context loss</a> may occur.</p> 7821cb0ef41Sopenharmony_ci 7831cb0ef41Sopenharmony_ci<pre class="with-64-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> diagnostics_channel <span class="hljs-keyword">from</span> <span class="hljs-string">'node:diagnostics_channel'</span>; 7841cb0ef41Sopenharmony_ci<span class="hljs-keyword">import</span> { <span class="hljs-title class_">AsyncLocalStorage</span> } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:async_hooks'</span>; 7851cb0ef41Sopenharmony_ci 7861cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> store = <span class="hljs-keyword">new</span> <span class="hljs-title class_">AsyncLocalStorage</span>(); 7871cb0ef41Sopenharmony_ci 7881cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> channel = diagnostics_channel.<span class="hljs-title function_">channel</span>(<span class="hljs-string">'my-channel'</span>); 7891cb0ef41Sopenharmony_ci 7901cb0ef41Sopenharmony_cichannel.<span class="hljs-title function_">bindStore</span>(store, <span class="hljs-function">(<span class="hljs-params">message</span>) =></span> { 7911cb0ef41Sopenharmony_ci <span class="hljs-keyword">const</span> parent = store.<span class="hljs-title function_">getStore</span>(); 7921cb0ef41Sopenharmony_ci <span class="hljs-keyword">return</span> <span class="hljs-keyword">new</span> <span class="hljs-title class_">Span</span>(message, parent); 7931cb0ef41Sopenharmony_ci}); 7941cb0ef41Sopenharmony_cichannel.<span class="hljs-title function_">runStores</span>({ <span class="hljs-attr">some</span>: <span class="hljs-string">'message'</span> }, <span class="hljs-function">() =></span> { 7951cb0ef41Sopenharmony_ci store.<span class="hljs-title function_">getStore</span>(); <span class="hljs-comment">// Span({ some: 'message' })</span> 7961cb0ef41Sopenharmony_ci});</code><code class="language-js cjs"><span class="hljs-keyword">const</span> diagnostics_channel = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:diagnostics_channel'</span>); 7971cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> { <span class="hljs-title class_">AsyncLocalStorage</span> } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:async_hooks'</span>); 7981cb0ef41Sopenharmony_ci 7991cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> store = <span class="hljs-keyword">new</span> <span class="hljs-title class_">AsyncLocalStorage</span>(); 8001cb0ef41Sopenharmony_ci 8011cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> channel = diagnostics_channel.<span class="hljs-title function_">channel</span>(<span class="hljs-string">'my-channel'</span>); 8021cb0ef41Sopenharmony_ci 8031cb0ef41Sopenharmony_cichannel.<span class="hljs-title function_">bindStore</span>(store, <span class="hljs-function">(<span class="hljs-params">message</span>) =></span> { 8041cb0ef41Sopenharmony_ci <span class="hljs-keyword">const</span> parent = store.<span class="hljs-title function_">getStore</span>(); 8051cb0ef41Sopenharmony_ci <span class="hljs-keyword">return</span> <span class="hljs-keyword">new</span> <span class="hljs-title class_">Span</span>(message, parent); 8061cb0ef41Sopenharmony_ci}); 8071cb0ef41Sopenharmony_cichannel.<span class="hljs-title function_">runStores</span>({ <span class="hljs-attr">some</span>: <span class="hljs-string">'message'</span> }, <span class="hljs-function">() =></span> { 8081cb0ef41Sopenharmony_ci store.<span class="hljs-title function_">getStore</span>(); <span class="hljs-comment">// Span({ some: 'message' })</span> 8091cb0ef41Sopenharmony_ci});</code><button class="copy-button">copy</button></pre> 8101cb0ef41Sopenharmony_ci<h4>Class: <code>TracingChannel</code><span><a class="mark" href="#class-tracingchannel" id="class-tracingchannel">#</a></span><a aria-hidden="true" class="legacy" id="diagnostics_channel_class_tracingchannel"></a></h4> 8111cb0ef41Sopenharmony_ci<div class="api_metadata"> 8121cb0ef41Sopenharmony_ci<span>Added in: v18.19.0</span> 8131cb0ef41Sopenharmony_ci</div> 8141cb0ef41Sopenharmony_ci<p></p><div class="api_stability api_stability_1"><a href="documentation.html#stability-index">Stability: 1</a> - Experimental</div><p></p> 8151cb0ef41Sopenharmony_ci<p>The class <code>TracingChannel</code> is a collection of <a href="#tracingchannel-channels">TracingChannel Channels</a> which 8161cb0ef41Sopenharmony_citogether express a single traceable action. It is used to formalize and 8171cb0ef41Sopenharmony_cisimplify the process of producing events for tracing application flow. 8181cb0ef41Sopenharmony_ci<a href="#diagnostics_channeltracingchannelnameorchannels"><code>diagnostics_channel.tracingChannel()</code></a> is used to construct a 8191cb0ef41Sopenharmony_ci<code>TracingChannel</code>. As with <code>Channel</code> it is recommended to create and reuse a 8201cb0ef41Sopenharmony_cisingle <code>TracingChannel</code> at the top-level of the file rather than creating them 8211cb0ef41Sopenharmony_cidynamically.</p> 8221cb0ef41Sopenharmony_ci<h5><code>tracingChannel.subscribe(subscribers)</code><span><a class="mark" href="#tracingchannelsubscribesubscribers" id="tracingchannelsubscribesubscribers">#</a></span><a aria-hidden="true" class="legacy" id="diagnostics_channel_tracingchannel_subscribe_subscribers"></a></h5> 8231cb0ef41Sopenharmony_ci<div class="api_metadata"> 8241cb0ef41Sopenharmony_ci<span>Added in: v18.19.0</span> 8251cb0ef41Sopenharmony_ci</div> 8261cb0ef41Sopenharmony_ci<p></p><div class="api_stability api_stability_1"><a href="documentation.html#stability-index">Stability: 1</a> - Experimental</div><p></p> 8271cb0ef41Sopenharmony_ci<ul> 8281cb0ef41Sopenharmony_ci<li><code>subscribers</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> Set of <a href="#tracingchannel-channels">TracingChannel Channels</a> subscribers 8291cb0ef41Sopenharmony_ci<ul> 8301cb0ef41Sopenharmony_ci<li><code>start</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> The <a href="#startevent"><code>start</code> event</a> subscriber</li> 8311cb0ef41Sopenharmony_ci<li><code>end</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> The <a href="#endevent"><code>end</code> event</a> subscriber</li> 8321cb0ef41Sopenharmony_ci<li><code>asyncStart</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> The <a href="#asyncstartevent"><code>asyncStart</code> event</a> subscriber</li> 8331cb0ef41Sopenharmony_ci<li><code>asyncEnd</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> The <a href="#asyncendevent"><code>asyncEnd</code> event</a> subscriber</li> 8341cb0ef41Sopenharmony_ci<li><code>error</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> The <a href="#errorevent"><code>error</code> event</a> subscriber</li> 8351cb0ef41Sopenharmony_ci</ul> 8361cb0ef41Sopenharmony_ci</li> 8371cb0ef41Sopenharmony_ci</ul> 8381cb0ef41Sopenharmony_ci<p>Helper to subscribe a collection of functions to the corresponding channels. 8391cb0ef41Sopenharmony_ciThis is the same as calling <a href="#channelsubscribeonmessage"><code>channel.subscribe(onMessage)</code></a> on each channel 8401cb0ef41Sopenharmony_ciindividually.</p> 8411cb0ef41Sopenharmony_ci 8421cb0ef41Sopenharmony_ci<pre class="with-64-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> diagnostics_channel <span class="hljs-keyword">from</span> <span class="hljs-string">'node:diagnostics_channel'</span>; 8431cb0ef41Sopenharmony_ci 8441cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> channels = diagnostics_channel.<span class="hljs-title function_">tracingChannel</span>(<span class="hljs-string">'my-channel'</span>); 8451cb0ef41Sopenharmony_ci 8461cb0ef41Sopenharmony_cichannels.<span class="hljs-title function_">subscribe</span>({ 8471cb0ef41Sopenharmony_ci <span class="hljs-title function_">start</span>(<span class="hljs-params">message</span>) { 8481cb0ef41Sopenharmony_ci <span class="hljs-comment">// Handle start message</span> 8491cb0ef41Sopenharmony_ci }, 8501cb0ef41Sopenharmony_ci <span class="hljs-title function_">end</span>(<span class="hljs-params">message</span>) { 8511cb0ef41Sopenharmony_ci <span class="hljs-comment">// Handle end message</span> 8521cb0ef41Sopenharmony_ci }, 8531cb0ef41Sopenharmony_ci <span class="hljs-title function_">asyncStart</span>(<span class="hljs-params">message</span>) { 8541cb0ef41Sopenharmony_ci <span class="hljs-comment">// Handle asyncStart message</span> 8551cb0ef41Sopenharmony_ci }, 8561cb0ef41Sopenharmony_ci <span class="hljs-title function_">asyncEnd</span>(<span class="hljs-params">message</span>) { 8571cb0ef41Sopenharmony_ci <span class="hljs-comment">// Handle asyncEnd message</span> 8581cb0ef41Sopenharmony_ci }, 8591cb0ef41Sopenharmony_ci <span class="hljs-title function_">error</span>(<span class="hljs-params">message</span>) { 8601cb0ef41Sopenharmony_ci <span class="hljs-comment">// Handle error message</span> 8611cb0ef41Sopenharmony_ci }, 8621cb0ef41Sopenharmony_ci});</code><code class="language-js cjs"><span class="hljs-keyword">const</span> diagnostics_channel = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:diagnostics_channel'</span>); 8631cb0ef41Sopenharmony_ci 8641cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> channels = diagnostics_channel.<span class="hljs-title function_">tracingChannel</span>(<span class="hljs-string">'my-channel'</span>); 8651cb0ef41Sopenharmony_ci 8661cb0ef41Sopenharmony_cichannels.<span class="hljs-title function_">subscribe</span>({ 8671cb0ef41Sopenharmony_ci <span class="hljs-title function_">start</span>(<span class="hljs-params">message</span>) { 8681cb0ef41Sopenharmony_ci <span class="hljs-comment">// Handle start message</span> 8691cb0ef41Sopenharmony_ci }, 8701cb0ef41Sopenharmony_ci <span class="hljs-title function_">end</span>(<span class="hljs-params">message</span>) { 8711cb0ef41Sopenharmony_ci <span class="hljs-comment">// Handle end message</span> 8721cb0ef41Sopenharmony_ci }, 8731cb0ef41Sopenharmony_ci <span class="hljs-title function_">asyncStart</span>(<span class="hljs-params">message</span>) { 8741cb0ef41Sopenharmony_ci <span class="hljs-comment">// Handle asyncStart message</span> 8751cb0ef41Sopenharmony_ci }, 8761cb0ef41Sopenharmony_ci <span class="hljs-title function_">asyncEnd</span>(<span class="hljs-params">message</span>) { 8771cb0ef41Sopenharmony_ci <span class="hljs-comment">// Handle asyncEnd message</span> 8781cb0ef41Sopenharmony_ci }, 8791cb0ef41Sopenharmony_ci <span class="hljs-title function_">error</span>(<span class="hljs-params">message</span>) { 8801cb0ef41Sopenharmony_ci <span class="hljs-comment">// Handle error message</span> 8811cb0ef41Sopenharmony_ci }, 8821cb0ef41Sopenharmony_ci});</code><button class="copy-button">copy</button></pre> 8831cb0ef41Sopenharmony_ci<h5><code>tracingChannel.unsubscribe(subscribers)</code><span><a class="mark" href="#tracingchannelunsubscribesubscribers" id="tracingchannelunsubscribesubscribers">#</a></span><a aria-hidden="true" class="legacy" id="diagnostics_channel_tracingchannel_unsubscribe_subscribers"></a></h5> 8841cb0ef41Sopenharmony_ci<div class="api_metadata"> 8851cb0ef41Sopenharmony_ci<span>Added in: v18.19.0</span> 8861cb0ef41Sopenharmony_ci</div> 8871cb0ef41Sopenharmony_ci<p></p><div class="api_stability api_stability_1"><a href="documentation.html#stability-index">Stability: 1</a> - Experimental</div><p></p> 8881cb0ef41Sopenharmony_ci<ul> 8891cb0ef41Sopenharmony_ci<li><code>subscribers</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> Set of <a href="#tracingchannel-channels">TracingChannel Channels</a> subscribers 8901cb0ef41Sopenharmony_ci<ul> 8911cb0ef41Sopenharmony_ci<li><code>start</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> The <a href="#startevent"><code>start</code> event</a> subscriber</li> 8921cb0ef41Sopenharmony_ci<li><code>end</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> The <a href="#endevent"><code>end</code> event</a> subscriber</li> 8931cb0ef41Sopenharmony_ci<li><code>asyncStart</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> The <a href="#asyncstartevent"><code>asyncStart</code> event</a> subscriber</li> 8941cb0ef41Sopenharmony_ci<li><code>asyncEnd</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> The <a href="#asyncendevent"><code>asyncEnd</code> event</a> subscriber</li> 8951cb0ef41Sopenharmony_ci<li><code>error</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> The <a href="#errorevent"><code>error</code> event</a> subscriber</li> 8961cb0ef41Sopenharmony_ci</ul> 8971cb0ef41Sopenharmony_ci</li> 8981cb0ef41Sopenharmony_ci<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> <code>true</code> if all handlers were successfully unsubscribed, 8991cb0ef41Sopenharmony_ciand <code>false</code> otherwise.</li> 9001cb0ef41Sopenharmony_ci</ul> 9011cb0ef41Sopenharmony_ci<p>Helper to unsubscribe a collection of functions from the corresponding channels. 9021cb0ef41Sopenharmony_ciThis is the same as calling <a href="#channelunsubscribeonmessage"><code>channel.unsubscribe(onMessage)</code></a> on each channel 9031cb0ef41Sopenharmony_ciindividually.</p> 9041cb0ef41Sopenharmony_ci 9051cb0ef41Sopenharmony_ci<pre class="with-64-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> diagnostics_channel <span class="hljs-keyword">from</span> <span class="hljs-string">'node:diagnostics_channel'</span>; 9061cb0ef41Sopenharmony_ci 9071cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> channels = diagnostics_channel.<span class="hljs-title function_">tracingChannel</span>(<span class="hljs-string">'my-channel'</span>); 9081cb0ef41Sopenharmony_ci 9091cb0ef41Sopenharmony_cichannels.<span class="hljs-title function_">unsubscribe</span>({ 9101cb0ef41Sopenharmony_ci <span class="hljs-title function_">start</span>(<span class="hljs-params">message</span>) { 9111cb0ef41Sopenharmony_ci <span class="hljs-comment">// Handle start message</span> 9121cb0ef41Sopenharmony_ci }, 9131cb0ef41Sopenharmony_ci <span class="hljs-title function_">end</span>(<span class="hljs-params">message</span>) { 9141cb0ef41Sopenharmony_ci <span class="hljs-comment">// Handle end message</span> 9151cb0ef41Sopenharmony_ci }, 9161cb0ef41Sopenharmony_ci <span class="hljs-title function_">asyncStart</span>(<span class="hljs-params">message</span>) { 9171cb0ef41Sopenharmony_ci <span class="hljs-comment">// Handle asyncStart message</span> 9181cb0ef41Sopenharmony_ci }, 9191cb0ef41Sopenharmony_ci <span class="hljs-title function_">asyncEnd</span>(<span class="hljs-params">message</span>) { 9201cb0ef41Sopenharmony_ci <span class="hljs-comment">// Handle asyncEnd message</span> 9211cb0ef41Sopenharmony_ci }, 9221cb0ef41Sopenharmony_ci <span class="hljs-title function_">error</span>(<span class="hljs-params">message</span>) { 9231cb0ef41Sopenharmony_ci <span class="hljs-comment">// Handle error message</span> 9241cb0ef41Sopenharmony_ci }, 9251cb0ef41Sopenharmony_ci});</code><code class="language-js cjs"><span class="hljs-keyword">const</span> diagnostics_channel = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:diagnostics_channel'</span>); 9261cb0ef41Sopenharmony_ci 9271cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> channels = diagnostics_channel.<span class="hljs-title function_">tracingChannel</span>(<span class="hljs-string">'my-channel'</span>); 9281cb0ef41Sopenharmony_ci 9291cb0ef41Sopenharmony_cichannels.<span class="hljs-title function_">unsubscribe</span>({ 9301cb0ef41Sopenharmony_ci <span class="hljs-title function_">start</span>(<span class="hljs-params">message</span>) { 9311cb0ef41Sopenharmony_ci <span class="hljs-comment">// Handle start message</span> 9321cb0ef41Sopenharmony_ci }, 9331cb0ef41Sopenharmony_ci <span class="hljs-title function_">end</span>(<span class="hljs-params">message</span>) { 9341cb0ef41Sopenharmony_ci <span class="hljs-comment">// Handle end message</span> 9351cb0ef41Sopenharmony_ci }, 9361cb0ef41Sopenharmony_ci <span class="hljs-title function_">asyncStart</span>(<span class="hljs-params">message</span>) { 9371cb0ef41Sopenharmony_ci <span class="hljs-comment">// Handle asyncStart message</span> 9381cb0ef41Sopenharmony_ci }, 9391cb0ef41Sopenharmony_ci <span class="hljs-title function_">asyncEnd</span>(<span class="hljs-params">message</span>) { 9401cb0ef41Sopenharmony_ci <span class="hljs-comment">// Handle asyncEnd message</span> 9411cb0ef41Sopenharmony_ci }, 9421cb0ef41Sopenharmony_ci <span class="hljs-title function_">error</span>(<span class="hljs-params">message</span>) { 9431cb0ef41Sopenharmony_ci <span class="hljs-comment">// Handle error message</span> 9441cb0ef41Sopenharmony_ci }, 9451cb0ef41Sopenharmony_ci});</code><button class="copy-button">copy</button></pre> 9461cb0ef41Sopenharmony_ci<h5><code>tracingChannel.traceSync(fn[, context[, thisArg[, ...args]]])</code><span><a class="mark" href="#tracingchanneltracesyncfn-context-thisarg-args" id="tracingchanneltracesyncfn-context-thisarg-args">#</a></span><a aria-hidden="true" class="legacy" id="diagnostics_channel_tracingchannel_tracesync_fn_context_thisarg_args"></a></h5> 9471cb0ef41Sopenharmony_ci<div class="api_metadata"> 9481cb0ef41Sopenharmony_ci<span>Added in: v18.19.0</span> 9491cb0ef41Sopenharmony_ci</div> 9501cb0ef41Sopenharmony_ci<p></p><div class="api_stability api_stability_1"><a href="documentation.html#stability-index">Stability: 1</a> - Experimental</div><p></p> 9511cb0ef41Sopenharmony_ci<ul> 9521cb0ef41Sopenharmony_ci<li><code>fn</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> Function to wrap a trace around</li> 9531cb0ef41Sopenharmony_ci<li><code>context</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> Shared object to correlate events through</li> 9541cb0ef41Sopenharmony_ci<li><code>thisArg</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a> The receiver to be used for the function call</li> 9551cb0ef41Sopenharmony_ci<li><code>...args</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a> Optional arguments to pass to the function</li> 9561cb0ef41Sopenharmony_ci<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a> The return value of the given function</li> 9571cb0ef41Sopenharmony_ci</ul> 9581cb0ef41Sopenharmony_ci<p>Trace a synchronous function call. This will always produce a <a href="#startevent"><code>start</code> event</a> 9591cb0ef41Sopenharmony_ciand <a href="#endevent"><code>end</code> event</a> around the execution and may produce an <a href="#errorevent"><code>error</code> event</a> 9601cb0ef41Sopenharmony_ciif the given function throws an error. This will run the given function using 9611cb0ef41Sopenharmony_ci<a href="#channelrunstorescontext-fn-thisarg-args"><code>channel.runStores(context, ...)</code></a> on the <code>start</code> channel which ensures all 9621cb0ef41Sopenharmony_cievents should have any bound stores set to match this trace context.</p> 9631cb0ef41Sopenharmony_ci 9641cb0ef41Sopenharmony_ci<pre class="with-64-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> diagnostics_channel <span class="hljs-keyword">from</span> <span class="hljs-string">'node:diagnostics_channel'</span>; 9651cb0ef41Sopenharmony_ci 9661cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> channels = diagnostics_channel.<span class="hljs-title function_">tracingChannel</span>(<span class="hljs-string">'my-channel'</span>); 9671cb0ef41Sopenharmony_ci 9681cb0ef41Sopenharmony_cichannels.<span class="hljs-title function_">traceSync</span>(<span class="hljs-function">() =></span> { 9691cb0ef41Sopenharmony_ci <span class="hljs-comment">// Do something</span> 9701cb0ef41Sopenharmony_ci}, { 9711cb0ef41Sopenharmony_ci <span class="hljs-attr">some</span>: <span class="hljs-string">'thing'</span>, 9721cb0ef41Sopenharmony_ci});</code><code class="language-js cjs"><span class="hljs-keyword">const</span> diagnostics_channel = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:diagnostics_channel'</span>); 9731cb0ef41Sopenharmony_ci 9741cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> channels = diagnostics_channel.<span class="hljs-title function_">tracingChannel</span>(<span class="hljs-string">'my-channel'</span>); 9751cb0ef41Sopenharmony_ci 9761cb0ef41Sopenharmony_cichannels.<span class="hljs-title function_">traceSync</span>(<span class="hljs-function">() =></span> { 9771cb0ef41Sopenharmony_ci <span class="hljs-comment">// Do something</span> 9781cb0ef41Sopenharmony_ci}, { 9791cb0ef41Sopenharmony_ci <span class="hljs-attr">some</span>: <span class="hljs-string">'thing'</span>, 9801cb0ef41Sopenharmony_ci});</code><button class="copy-button">copy</button></pre> 9811cb0ef41Sopenharmony_ci<h5><code>tracingChannel.tracePromise(fn[, context[, thisArg[, ...args]]])</code><span><a class="mark" href="#tracingchanneltracepromisefn-context-thisarg-args" id="tracingchanneltracepromisefn-context-thisarg-args">#</a></span><a aria-hidden="true" class="legacy" id="diagnostics_channel_tracingchannel_tracepromise_fn_context_thisarg_args"></a></h5> 9821cb0ef41Sopenharmony_ci<div class="api_metadata"> 9831cb0ef41Sopenharmony_ci<span>Added in: v18.19.0</span> 9841cb0ef41Sopenharmony_ci</div> 9851cb0ef41Sopenharmony_ci<p></p><div class="api_stability api_stability_1"><a href="documentation.html#stability-index">Stability: 1</a> - Experimental</div><p></p> 9861cb0ef41Sopenharmony_ci<ul> 9871cb0ef41Sopenharmony_ci<li><code>fn</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> Promise-returning function to wrap a trace around</li> 9881cb0ef41Sopenharmony_ci<li><code>context</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> Shared object to correlate trace events through</li> 9891cb0ef41Sopenharmony_ci<li><code>thisArg</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a> The receiver to be used for the function call</li> 9901cb0ef41Sopenharmony_ci<li><code>...args</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a> Optional arguments to pass to the function</li> 9911cb0ef41Sopenharmony_ci<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise" class="type"><Promise></a> Chained from promise returned by the given function</li> 9921cb0ef41Sopenharmony_ci</ul> 9931cb0ef41Sopenharmony_ci<p>Trace a promise-returning function call. This will always produce a 9941cb0ef41Sopenharmony_ci<a href="#startevent"><code>start</code> event</a> and <a href="#endevent"><code>end</code> event</a> around the synchronous portion of the 9951cb0ef41Sopenharmony_cifunction execution, and will produce an <a href="#asyncstartevent"><code>asyncStart</code> event</a> and 9961cb0ef41Sopenharmony_ci<a href="#asyncendevent"><code>asyncEnd</code> event</a> when a promise continuation is reached. It may also 9971cb0ef41Sopenharmony_ciproduce an <a href="#errorevent"><code>error</code> event</a> if the given function throws an error or the 9981cb0ef41Sopenharmony_cireturned promise rejects. This will run the given function using 9991cb0ef41Sopenharmony_ci<a href="#channelrunstorescontext-fn-thisarg-args"><code>channel.runStores(context, ...)</code></a> on the <code>start</code> channel which ensures all 10001cb0ef41Sopenharmony_cievents should have any bound stores set to match this trace context.</p> 10011cb0ef41Sopenharmony_ci 10021cb0ef41Sopenharmony_ci<pre class="with-64-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> diagnostics_channel <span class="hljs-keyword">from</span> <span class="hljs-string">'node:diagnostics_channel'</span>; 10031cb0ef41Sopenharmony_ci 10041cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> channels = diagnostics_channel.<span class="hljs-title function_">tracingChannel</span>(<span class="hljs-string">'my-channel'</span>); 10051cb0ef41Sopenharmony_ci 10061cb0ef41Sopenharmony_cichannels.<span class="hljs-title function_">tracePromise</span>(<span class="hljs-keyword">async</span> () => { 10071cb0ef41Sopenharmony_ci <span class="hljs-comment">// Do something</span> 10081cb0ef41Sopenharmony_ci}, { 10091cb0ef41Sopenharmony_ci <span class="hljs-attr">some</span>: <span class="hljs-string">'thing'</span>, 10101cb0ef41Sopenharmony_ci});</code><code class="language-js cjs"><span class="hljs-keyword">const</span> diagnostics_channel = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:diagnostics_channel'</span>); 10111cb0ef41Sopenharmony_ci 10121cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> channels = diagnostics_channel.<span class="hljs-title function_">tracingChannel</span>(<span class="hljs-string">'my-channel'</span>); 10131cb0ef41Sopenharmony_ci 10141cb0ef41Sopenharmony_cichannels.<span class="hljs-title function_">tracePromise</span>(<span class="hljs-keyword">async</span> () => { 10151cb0ef41Sopenharmony_ci <span class="hljs-comment">// Do something</span> 10161cb0ef41Sopenharmony_ci}, { 10171cb0ef41Sopenharmony_ci <span class="hljs-attr">some</span>: <span class="hljs-string">'thing'</span>, 10181cb0ef41Sopenharmony_ci});</code><button class="copy-button">copy</button></pre> 10191cb0ef41Sopenharmony_ci<h5><code>tracingChannel.traceCallback(fn[, position[, context[, thisArg[, ...args]]]])</code><span><a class="mark" href="#tracingchanneltracecallbackfn-position-context-thisarg-args" id="tracingchanneltracecallbackfn-position-context-thisarg-args">#</a></span><a aria-hidden="true" class="legacy" id="diagnostics_channel_tracingchannel_tracecallback_fn_position_context_thisarg_args"></a></h5> 10201cb0ef41Sopenharmony_ci<div class="api_metadata"> 10211cb0ef41Sopenharmony_ci<span>Added in: v18.19.0</span> 10221cb0ef41Sopenharmony_ci</div> 10231cb0ef41Sopenharmony_ci<p></p><div class="api_stability api_stability_1"><a href="documentation.html#stability-index">Stability: 1</a> - Experimental</div><p></p> 10241cb0ef41Sopenharmony_ci<ul> 10251cb0ef41Sopenharmony_ci<li><code>fn</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> callback using function to wrap a trace around</li> 10261cb0ef41Sopenharmony_ci<li><code>position</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Zero-indexed argument position of expected callback</li> 10271cb0ef41Sopenharmony_ci<li><code>context</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> Shared object to correlate trace events through</li> 10281cb0ef41Sopenharmony_ci<li><code>thisArg</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a> The receiver to be used for the function call</li> 10291cb0ef41Sopenharmony_ci<li><code>...args</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a> Optional arguments to pass to the function</li> 10301cb0ef41Sopenharmony_ci<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a> The return value of the given function</li> 10311cb0ef41Sopenharmony_ci</ul> 10321cb0ef41Sopenharmony_ci<p>Trace a callback-receiving function call. This will always produce a 10331cb0ef41Sopenharmony_ci<a href="#startevent"><code>start</code> event</a> and <a href="#endevent"><code>end</code> event</a> around the synchronous portion of the 10341cb0ef41Sopenharmony_cifunction execution, and will produce a <a href="#asyncstartevent"><code>asyncStart</code> event</a> and 10351cb0ef41Sopenharmony_ci<a href="#asyncendevent"><code>asyncEnd</code> event</a> around the callback execution. It may also produce an 10361cb0ef41Sopenharmony_ci<a href="#errorevent"><code>error</code> event</a> if the given function throws an error or the returned 10371cb0ef41Sopenharmony_cipromise rejects. This will run the given function using 10381cb0ef41Sopenharmony_ci<a href="#channelrunstorescontext-fn-thisarg-args"><code>channel.runStores(context, ...)</code></a> on the <code>start</code> channel which ensures all 10391cb0ef41Sopenharmony_cievents should have any bound stores set to match this trace context.</p> 10401cb0ef41Sopenharmony_ci<p>The <code>position</code> will be -1 by default to indicate the final argument should 10411cb0ef41Sopenharmony_cibe used as the callback.</p> 10421cb0ef41Sopenharmony_ci 10431cb0ef41Sopenharmony_ci<pre class="with-64-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> diagnostics_channel <span class="hljs-keyword">from</span> <span class="hljs-string">'node:diagnostics_channel'</span>; 10441cb0ef41Sopenharmony_ci 10451cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> channels = diagnostics_channel.<span class="hljs-title function_">tracingChannel</span>(<span class="hljs-string">'my-channel'</span>); 10461cb0ef41Sopenharmony_ci 10471cb0ef41Sopenharmony_cichannels.<span class="hljs-title function_">traceCallback</span>(<span class="hljs-function">(<span class="hljs-params">arg1, callback</span>) =></span> { 10481cb0ef41Sopenharmony_ci <span class="hljs-comment">// Do something</span> 10491cb0ef41Sopenharmony_ci <span class="hljs-title function_">callback</span>(<span class="hljs-literal">null</span>, <span class="hljs-string">'result'</span>); 10501cb0ef41Sopenharmony_ci}, <span class="hljs-number">1</span>, { 10511cb0ef41Sopenharmony_ci <span class="hljs-attr">some</span>: <span class="hljs-string">'thing'</span>, 10521cb0ef41Sopenharmony_ci}, thisArg, arg1, callback);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> diagnostics_channel = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:diagnostics_channel'</span>); 10531cb0ef41Sopenharmony_ci 10541cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> channels = diagnostics_channel.<span class="hljs-title function_">tracingChannel</span>(<span class="hljs-string">'my-channel'</span>); 10551cb0ef41Sopenharmony_ci 10561cb0ef41Sopenharmony_cichannels.<span class="hljs-title function_">traceCallback</span>(<span class="hljs-function">(<span class="hljs-params">arg1, callback</span>) =></span> { 10571cb0ef41Sopenharmony_ci <span class="hljs-comment">// Do something</span> 10581cb0ef41Sopenharmony_ci <span class="hljs-title function_">callback</span>(<span class="hljs-literal">null</span>, <span class="hljs-string">'result'</span>); 10591cb0ef41Sopenharmony_ci}, { 10601cb0ef41Sopenharmony_ci <span class="hljs-attr">some</span>: <span class="hljs-string">'thing'</span>, 10611cb0ef41Sopenharmony_ci}, thisArg, arg1, callback);</code><button class="copy-button">copy</button></pre> 10621cb0ef41Sopenharmony_ci<p>The callback will also be run with <a href="#channelrunstorescontext-fn-thisarg-args"><code>channel.runStores(context, ...)</code></a> which 10631cb0ef41Sopenharmony_cienables context loss recovery in some cases.</p> 10641cb0ef41Sopenharmony_ci 10651cb0ef41Sopenharmony_ci<pre class="with-64-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> diagnostics_channel <span class="hljs-keyword">from</span> <span class="hljs-string">'node:diagnostics_channel'</span>; 10661cb0ef41Sopenharmony_ci<span class="hljs-keyword">import</span> { <span class="hljs-title class_">AsyncLocalStorage</span> } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:async_hooks'</span>; 10671cb0ef41Sopenharmony_ci 10681cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> channels = diagnostics_channel.<span class="hljs-title function_">tracingChannel</span>(<span class="hljs-string">'my-channel'</span>); 10691cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> myStore = <span class="hljs-keyword">new</span> <span class="hljs-title class_">AsyncLocalStorage</span>(); 10701cb0ef41Sopenharmony_ci 10711cb0ef41Sopenharmony_ci<span class="hljs-comment">// The start channel sets the initial store data to something</span> 10721cb0ef41Sopenharmony_ci<span class="hljs-comment">// and stores that store data value on the trace context object</span> 10731cb0ef41Sopenharmony_cichannels.<span class="hljs-property">start</span>.<span class="hljs-title function_">bindStore</span>(myStore, <span class="hljs-function">(<span class="hljs-params">data</span>) =></span> { 10741cb0ef41Sopenharmony_ci <span class="hljs-keyword">const</span> span = <span class="hljs-keyword">new</span> <span class="hljs-title class_">Span</span>(data); 10751cb0ef41Sopenharmony_ci data.<span class="hljs-property">span</span> = span; 10761cb0ef41Sopenharmony_ci <span class="hljs-keyword">return</span> span; 10771cb0ef41Sopenharmony_ci}); 10781cb0ef41Sopenharmony_ci 10791cb0ef41Sopenharmony_ci<span class="hljs-comment">// Then asyncStart can restore from that data it stored previously</span> 10801cb0ef41Sopenharmony_cichannels.<span class="hljs-property">asyncStart</span>.<span class="hljs-title function_">bindStore</span>(myStore, <span class="hljs-function">(<span class="hljs-params">data</span>) =></span> { 10811cb0ef41Sopenharmony_ci <span class="hljs-keyword">return</span> data.<span class="hljs-property">span</span>; 10821cb0ef41Sopenharmony_ci});</code><code class="language-js cjs"><span class="hljs-keyword">const</span> diagnostics_channel = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:diagnostics_channel'</span>); 10831cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> { <span class="hljs-title class_">AsyncLocalStorage</span> } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:async_hooks'</span>); 10841cb0ef41Sopenharmony_ci 10851cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> channels = diagnostics_channel.<span class="hljs-title function_">tracingChannel</span>(<span class="hljs-string">'my-channel'</span>); 10861cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> myStore = <span class="hljs-keyword">new</span> <span class="hljs-title class_">AsyncLocalStorage</span>(); 10871cb0ef41Sopenharmony_ci 10881cb0ef41Sopenharmony_ci<span class="hljs-comment">// The start channel sets the initial store data to something</span> 10891cb0ef41Sopenharmony_ci<span class="hljs-comment">// and stores that store data value on the trace context object</span> 10901cb0ef41Sopenharmony_cichannels.<span class="hljs-property">start</span>.<span class="hljs-title function_">bindStore</span>(myStore, <span class="hljs-function">(<span class="hljs-params">data</span>) =></span> { 10911cb0ef41Sopenharmony_ci <span class="hljs-keyword">const</span> span = <span class="hljs-keyword">new</span> <span class="hljs-title class_">Span</span>(data); 10921cb0ef41Sopenharmony_ci data.<span class="hljs-property">span</span> = span; 10931cb0ef41Sopenharmony_ci <span class="hljs-keyword">return</span> span; 10941cb0ef41Sopenharmony_ci}); 10951cb0ef41Sopenharmony_ci 10961cb0ef41Sopenharmony_ci<span class="hljs-comment">// Then asyncStart can restore from that data it stored previously</span> 10971cb0ef41Sopenharmony_cichannels.<span class="hljs-property">asyncStart</span>.<span class="hljs-title function_">bindStore</span>(myStore, <span class="hljs-function">(<span class="hljs-params">data</span>) =></span> { 10981cb0ef41Sopenharmony_ci <span class="hljs-keyword">return</span> data.<span class="hljs-property">span</span>; 10991cb0ef41Sopenharmony_ci});</code><button class="copy-button">copy</button></pre> 11001cb0ef41Sopenharmony_ci<h4>TracingChannel Channels<span><a class="mark" href="#tracingchannel-channels" id="tracingchannel-channels">#</a></span><a aria-hidden="true" class="legacy" id="diagnostics_channel_tracingchannel_channels"></a></h4> 11011cb0ef41Sopenharmony_ci<p>A TracingChannel is a collection of several diagnostics_channels representing 11021cb0ef41Sopenharmony_cispecific points in the execution lifecycle of a single traceable action. The 11031cb0ef41Sopenharmony_cibehaviour is split into five diagnostics_channels consisting of <code>start</code>, 11041cb0ef41Sopenharmony_ci<code>end</code>, <code>asyncStart</code>, <code>asyncEnd</code>, and <code>error</code>. A single traceable action will 11051cb0ef41Sopenharmony_cishare the same event object between all events, this can be helpful for 11061cb0ef41Sopenharmony_cimanaging correlation through a weakmap.</p> 11071cb0ef41Sopenharmony_ci<p>These event objects will be extended with <code>result</code> or <code>error</code> values when 11081cb0ef41Sopenharmony_cithe task "completes". In the case of a synchronous task the <code>result</code> will be 11091cb0ef41Sopenharmony_cithe return value and the <code>error</code> will be anything thrown from the function. 11101cb0ef41Sopenharmony_ciWith callback-based async functions the <code>result</code> will be the second argument 11111cb0ef41Sopenharmony_ciof the callback while the <code>error</code> will either be a thrown error visible in the 11121cb0ef41Sopenharmony_ci<code>end</code> event or the first callback argument in either of the <code>asyncStart</code> or 11131cb0ef41Sopenharmony_ci<code>asyncEnd</code> events.</p> 11141cb0ef41Sopenharmony_ci<p>Tracing channels should follow a naming pattern of:</p> 11151cb0ef41Sopenharmony_ci<ul> 11161cb0ef41Sopenharmony_ci<li><code>tracing:module.class.method:start</code> or <code>tracing:module.function:start</code></li> 11171cb0ef41Sopenharmony_ci<li><code>tracing:module.class.method:end</code> or <code>tracing:module.function:end</code></li> 11181cb0ef41Sopenharmony_ci<li><code>tracing:module.class.method:asyncStart</code> or <code>tracing:module.function:asyncStart</code></li> 11191cb0ef41Sopenharmony_ci<li><code>tracing:module.class.method:asyncEnd</code> or <code>tracing:module.function:asyncEnd</code></li> 11201cb0ef41Sopenharmony_ci<li><code>tracing:module.class.method:error</code> or <code>tracing:module.function:error</code></li> 11211cb0ef41Sopenharmony_ci</ul> 11221cb0ef41Sopenharmony_ci<h5><code>start(event)</code><span><a class="mark" href="#startevent" id="startevent">#</a></span><a aria-hidden="true" class="legacy" id="diagnostics_channel_start_event"></a></h5> 11231cb0ef41Sopenharmony_ci<ul> 11241cb0ef41Sopenharmony_ci<li>Name: <code>tracing:${name}:start</code></li> 11251cb0ef41Sopenharmony_ci</ul> 11261cb0ef41Sopenharmony_ci<p>The <code>start</code> event represents the point at which a function is called. At this 11271cb0ef41Sopenharmony_cipoint the event data may contain function arguments or anything else available 11281cb0ef41Sopenharmony_ciat the very start of the execution of the function.</p> 11291cb0ef41Sopenharmony_ci<h5><code>end(event)</code><span><a class="mark" href="#endevent" id="endevent">#</a></span><a aria-hidden="true" class="legacy" id="diagnostics_channel_end_event"></a></h5> 11301cb0ef41Sopenharmony_ci<ul> 11311cb0ef41Sopenharmony_ci<li>Name: <code>tracing:${name}:end</code></li> 11321cb0ef41Sopenharmony_ci</ul> 11331cb0ef41Sopenharmony_ci<p>The <code>end</code> event represents the point at which a function call returns a value. 11341cb0ef41Sopenharmony_ciIn the case of an async function this is when the promise returned not when the 11351cb0ef41Sopenharmony_cifunction itself makes a return statement internally. At this point, if the 11361cb0ef41Sopenharmony_citraced function was synchronous the <code>result</code> field will be set to the return 11371cb0ef41Sopenharmony_civalue of the function. Alternatively, the <code>error</code> field may be present to 11381cb0ef41Sopenharmony_cirepresent any thrown errors.</p> 11391cb0ef41Sopenharmony_ci<p>It is recommended to listen specifically to the <code>error</code> event to track errors 11401cb0ef41Sopenharmony_cias it may be possible for a traceable action to produce multiple errors. For 11411cb0ef41Sopenharmony_ciexample, an async task which fails may be started internally before the sync 11421cb0ef41Sopenharmony_cipart of the task then throws an error.</p> 11431cb0ef41Sopenharmony_ci<h5><code>asyncStart(event)</code><span><a class="mark" href="#asyncstartevent" id="asyncstartevent">#</a></span><a aria-hidden="true" class="legacy" id="diagnostics_channel_asyncstart_event"></a></h5> 11441cb0ef41Sopenharmony_ci<ul> 11451cb0ef41Sopenharmony_ci<li>Name: <code>tracing:${name}:asyncStart</code></li> 11461cb0ef41Sopenharmony_ci</ul> 11471cb0ef41Sopenharmony_ci<p>The <code>asyncStart</code> event represents the callback or continuation of a traceable 11481cb0ef41Sopenharmony_cifunction being reached. At this point things like callback arguments may be 11491cb0ef41Sopenharmony_ciavailable, or anything else expressing the "result" of the action.</p> 11501cb0ef41Sopenharmony_ci<p>For callbacks-based functions, the first argument of the callback will be 11511cb0ef41Sopenharmony_ciassigned to the <code>error</code> field, if not <code>undefined</code> or <code>null</code>, and the second 11521cb0ef41Sopenharmony_ciargument will be assigned to the <code>result</code> field.</p> 11531cb0ef41Sopenharmony_ci<p>For promises, the argument to the <code>resolve</code> path will be assigned to <code>result</code> 11541cb0ef41Sopenharmony_cior the argument to the <code>reject</code> path will be assign to <code>error</code>.</p> 11551cb0ef41Sopenharmony_ci<p>It is recommended to listen specifically to the <code>error</code> event to track errors 11561cb0ef41Sopenharmony_cias it may be possible for a traceable action to produce multiple errors. For 11571cb0ef41Sopenharmony_ciexample, an async task which fails may be started internally before the sync 11581cb0ef41Sopenharmony_cipart of the task then throws an error.</p> 11591cb0ef41Sopenharmony_ci<h5><code>asyncEnd(event)</code><span><a class="mark" href="#asyncendevent" id="asyncendevent">#</a></span><a aria-hidden="true" class="legacy" id="diagnostics_channel_asyncend_event"></a></h5> 11601cb0ef41Sopenharmony_ci<ul> 11611cb0ef41Sopenharmony_ci<li>Name: <code>tracing:${name}:asyncEnd</code></li> 11621cb0ef41Sopenharmony_ci</ul> 11631cb0ef41Sopenharmony_ci<p>The <code>asyncEnd</code> event represents the callback of an asynchronous function 11641cb0ef41Sopenharmony_cireturning. It's not likely event data will change after the <code>asyncStart</code> event, 11651cb0ef41Sopenharmony_cihowever it may be useful to see the point where the callback completes.</p> 11661cb0ef41Sopenharmony_ci<h5><code>error(event)</code><span><a class="mark" href="#errorevent" id="errorevent">#</a></span><a aria-hidden="true" class="legacy" id="diagnostics_channel_error_event"></a></h5> 11671cb0ef41Sopenharmony_ci<ul> 11681cb0ef41Sopenharmony_ci<li>Name: <code>tracing:${name}:error</code></li> 11691cb0ef41Sopenharmony_ci</ul> 11701cb0ef41Sopenharmony_ci<p>The <code>error</code> event represents any error produced by the traceable function 11711cb0ef41Sopenharmony_cieither synchronously or asynchronously. If an error is thrown in the 11721cb0ef41Sopenharmony_cisynchronous portion of the traced function the error will be assigned to the 11731cb0ef41Sopenharmony_ci<code>error</code> field of the event and the <code>error</code> event will be triggered. If an error 11741cb0ef41Sopenharmony_ciis received asynchronously through a callback or promise rejection it will also 11751cb0ef41Sopenharmony_cibe assigned to the <code>error</code> field of the event and trigger the <code>error</code> event.</p> 11761cb0ef41Sopenharmony_ci<p>It is possible for a single traceable function call to produce errors multiple 11771cb0ef41Sopenharmony_citimes so this should be considered when consuming this event. For example, if 11781cb0ef41Sopenharmony_cianother async task is triggered internally which fails and then the sync part 11791cb0ef41Sopenharmony_ciof the function then throws and error two <code>error</code> events will be emitted, one 11801cb0ef41Sopenharmony_cifor the sync error and one for the async error.</p> 11811cb0ef41Sopenharmony_ci<h4>Built-in Channels<span><a class="mark" href="#built-in-channels" id="built-in-channels">#</a></span><a aria-hidden="true" class="legacy" id="diagnostics_channel_built_in_channels"></a></h4> 11821cb0ef41Sopenharmony_ci<p></p><div class="api_stability api_stability_1"><a href="documentation.html#stability-index">Stability: 1</a> - Experimental</div><p></p> 11831cb0ef41Sopenharmony_ci<p>While the diagnostics_channel API is now considered stable, the built-in 11841cb0ef41Sopenharmony_cichannels currently available are not. Each channel must be declared stable 11851cb0ef41Sopenharmony_ciindependently.</p> 11861cb0ef41Sopenharmony_ci<h5>HTTP<span><a class="mark" href="#http" id="http">#</a></span><a aria-hidden="true" class="legacy" id="diagnostics_channel_http"></a></h5> 11871cb0ef41Sopenharmony_ci<p><code>http.client.request.start</code></p> 11881cb0ef41Sopenharmony_ci<ul> 11891cb0ef41Sopenharmony_ci<li><code>request</code> <a href="http.html#class-httpclientrequest" class="type"><http.ClientRequest></a></li> 11901cb0ef41Sopenharmony_ci</ul> 11911cb0ef41Sopenharmony_ci<p>Emitted when client starts a request.</p> 11921cb0ef41Sopenharmony_ci<p><code>http.client.response.finish</code></p> 11931cb0ef41Sopenharmony_ci<ul> 11941cb0ef41Sopenharmony_ci<li><code>request</code> <a href="http.html#class-httpclientrequest" class="type"><http.ClientRequest></a></li> 11951cb0ef41Sopenharmony_ci<li><code>response</code> <a href="http.html#class-httpincomingmessage" class="type"><http.IncomingMessage></a></li> 11961cb0ef41Sopenharmony_ci</ul> 11971cb0ef41Sopenharmony_ci<p>Emitted when client receives a response.</p> 11981cb0ef41Sopenharmony_ci<p><code>http.server.request.start</code></p> 11991cb0ef41Sopenharmony_ci<ul> 12001cb0ef41Sopenharmony_ci<li><code>request</code> <a href="http.html#class-httpincomingmessage" class="type"><http.IncomingMessage></a></li> 12011cb0ef41Sopenharmony_ci<li><code>response</code> <a href="http.html#class-httpserverresponse" class="type"><http.ServerResponse></a></li> 12021cb0ef41Sopenharmony_ci<li><code>socket</code> <a href="net.html#class-netsocket" class="type"><net.Socket></a></li> 12031cb0ef41Sopenharmony_ci<li><code>server</code> <a href="http.html#class-httpserver" class="type"><http.Server></a></li> 12041cb0ef41Sopenharmony_ci</ul> 12051cb0ef41Sopenharmony_ci<p>Emitted when server receives a request.</p> 12061cb0ef41Sopenharmony_ci<p><code>http.server.response.finish</code></p> 12071cb0ef41Sopenharmony_ci<ul> 12081cb0ef41Sopenharmony_ci<li><code>request</code> <a href="http.html#class-httpincomingmessage" class="type"><http.IncomingMessage></a></li> 12091cb0ef41Sopenharmony_ci<li><code>response</code> <a href="http.html#class-httpserverresponse" class="type"><http.ServerResponse></a></li> 12101cb0ef41Sopenharmony_ci<li><code>socket</code> <a href="net.html#class-netsocket" class="type"><net.Socket></a></li> 12111cb0ef41Sopenharmony_ci<li><code>server</code> <a href="http.html#class-httpserver" class="type"><http.Server></a></li> 12121cb0ef41Sopenharmony_ci</ul> 12131cb0ef41Sopenharmony_ci<p>Emitted when server sends a response.</p> 12141cb0ef41Sopenharmony_ci<p><code>net.client.socket</code></p> 12151cb0ef41Sopenharmony_ci<ul> 12161cb0ef41Sopenharmony_ci<li><code>socket</code> <a href="net.html#class-netsocket" class="type"><net.Socket></a></li> 12171cb0ef41Sopenharmony_ci</ul> 12181cb0ef41Sopenharmony_ci<p>Emitted when a new TCP or pipe client socket is created.</p> 12191cb0ef41Sopenharmony_ci<p><code>net.server.socket</code></p> 12201cb0ef41Sopenharmony_ci<ul> 12211cb0ef41Sopenharmony_ci<li><code>socket</code> <a href="net.html#class-netsocket" class="type"><net.Socket></a></li> 12221cb0ef41Sopenharmony_ci</ul> 12231cb0ef41Sopenharmony_ci<p>Emitted when a new TCP or pipe connection is received.</p> 12241cb0ef41Sopenharmony_ci<p><code>udp.socket</code></p> 12251cb0ef41Sopenharmony_ci<ul> 12261cb0ef41Sopenharmony_ci<li><code>socket</code> <a href="dgram.html#class-dgramsocket" class="type"><dgram.Socket></a></li> 12271cb0ef41Sopenharmony_ci</ul> 12281cb0ef41Sopenharmony_ci<p>Emitted when a new UDP socket is created.</p></section> 12291cb0ef41Sopenharmony_ci <!-- API END --> 12301cb0ef41Sopenharmony_ci </div> 12311cb0ef41Sopenharmony_ci </div> 12321cb0ef41Sopenharmony_ci </div> 12331cb0ef41Sopenharmony_ci</body> 12341cb0ef41Sopenharmony_ci</html> 1235