Node.js v16.20.0 文档

跟踪事件#

¥Trace events

源代码: lib/trace_events.js

node:trace_events 模块提供了一种机制来集中 V8、Node.js 核心和用户空间代码生成的跟踪信息。

¥The node:trace_events module provides a mechanism to centralize tracing information generated by V8, Node.js core, and userspace code.

可以使用 --trace-event-categories 命令行标志或使用 node:trace_events 模块启用跟踪。--trace-event-categories 标志接受以逗号分隔的类别名称列表。

¥Tracing can be enabled with the --trace-event-categories command-line flag or by using the node:trace_events module. The --trace-event-categories flag accepts a list of comma-separated category names.

可用的类别是：

¥The available categories are:

• node：一个空的占位符。

  ¥node: An empty placeholder.

• node.async_hooks：启用详细的 async_hooks 跟踪数据的捕获。async_hooks 事件具有独特的 asyncId 和特殊的 triggerId triggerAsyncId 属性。

  ¥node.async_hooks: Enables capture of detailed async_hooks trace data. The async_hooks events have a unique asyncId and a special triggerId triggerAsyncId property.

• node.bootstrap：启用 Node.js 引导程序里程碑的捕获。

  ¥node.bootstrap: Enables capture of Node.js bootstrap milestones.

• node.console：启用 console.time() 和 console.count() 输出的捕获。

  ¥node.console: Enables capture of console.time() and console.count() output.

• node.dns.native：启用 DNS 查询的跟踪数据捕获。

  ¥node.dns.native: Enables capture of trace data for DNS queries.

• node.net.native：启用网络跟踪数据的捕获。

  ¥node.net.native: Enables capture of trace data for network.

• node.environment：启用 Node.js 环境里程碑的捕获。

  ¥node.environment: Enables capture of Node.js Environment milestones.

• node.fs.sync：启用文件系统同步方法的跟踪数据捕获。

  ¥node.fs.sync: Enables capture of trace data for file system sync methods.

• node.fs_dir.sync：启用文件系统同步目录方法的跟踪数据捕获。

  ¥node.fs_dir.sync: Enables capture of trace data for file system sync directory methods.

• node.fs.async：启用文件系统异步方法的跟踪数据捕获。

  ¥node.fs.async: Enables capture of trace data for file system async methods.

• node.fs_dir.async：启用文件系统异步目录方法的跟踪数据捕获。

  ¥node.fs_dir.async: Enables capture of trace data for file system async directory methods.

• node.perf：启用 性能接口 测量的捕获。

  ¥node.perf: Enables capture of Performance API measurements.

  • node.perf.usertiming：仅允许捕获 Performance API User Timing 度量和标记。

    ¥node.perf.usertiming: Enables capture of only Performance API User Timing measures and marks.

  • node.perf.timerify：启用仅捕获性能 API timerify 测量。

    ¥node.perf.timerify: Enables capture of only Performance API timerify measurements.

• node.promises.rejections：启用跟踪数据的捕获，跟踪未处理的 Promise 拒绝和处理后拒绝的数量。

  ¥node.promises.rejections: Enables capture of trace data tracking the number of unhandled Promise rejections and handled-after-rejections.

• node.vm.script：启用 node:vm 模块的 runInNewContext()、runInContext() 和 runInThisContext() 方法的跟踪数据捕获。

  ¥node.vm.script: Enables capture of trace data for the node:vm module's runInNewContext(), runInContext(), and runInThisContext() methods.

• v8：V8 事件与 GC、编译和执行相关。

  ¥v8: The V8 events are GC, compiling, and execution related.

• node.http：启用对 http 请求/响应的跟踪数据的捕获。

  ¥node.http: Enables capture of trace data for http request / response.

默认情况下，启用 node、node.async_hooks 和 v8 类别。

¥By default the node, node.async_hooks, and v8 categories are enabled.

node --trace-event-categories v8,node,node.async_hooks server.js 拷贝

早期版本的 Node.js 需要使用 --trace-events-enabled 标志来启用跟踪事件。此要求已被删除。但是，--trace-events-enabled 标志仍可使用，默认情况下将启用 node、node.async_hooks 和 v8 跟踪事件类别。

¥Prior versions of Node.js required the use of the --trace-events-enabled flag to enable trace events. This requirement has been removed. However, the --trace-events-enabled flag may still be used and will enable the node, node.async_hooks, and v8 trace event categories by default.

node --trace-events-enabled

# is equivalent to

node --trace-event-categories v8,node,node.async_hooks 拷贝

或者，可以使用 node:trace_events 模块启用跟踪事件：

¥Alternatively, trace events may be enabled using the node:trace_events module:

const trace_events = require('node:trace_events');
const tracing = trace_events.createTracing({ categories: ['node.perf'] });
tracing.enable();  // Enable trace event capture for the 'node.perf' category

// do work

tracing.disable();  // Disable trace event capture for the 'node.perf' category 拷贝

在启用跟踪的情况下运行 Node.js 将生成可以在 Chrome 的 chrome://tracing 选项卡中打开的日志文件。

¥Running Node.js with tracing enabled will produce log files that can be opened in the chrome://tracing tab of Chrome.

日志文件默认名为 node_trace.${rotation}.log，其中 ${rotation} 是一个递增的日志循环 ID。文件路径模式可以用 --trace-event-file-pattern 指定，它接受支持 ${rotation} 和 ${pid} 的模板字符串：

¥The logging file is by default called node_trace.${rotation}.log, where ${rotation} is an incrementing log-rotation id. The filepath pattern can be specified with --trace-event-file-pattern that accepts a template string that supports ${rotation} and ${pid}:

node --trace-event-categories v8 --trace-event-file-pattern '${pid}-${rotation}.log' server.js 拷贝

为保证在 SIGINT、SIGTERM 或 SIGBREAK 等信号事件后正确生成日志文件，请确保代码中有适当的处理程序，例如：

¥To guarantee that the log file is properly generated after signal events like SIGINT, SIGTERM, or SIGBREAK, make sure to have the appropriate handlers in your code, such as:

process.on('SIGINT', function onSigint() {
  console.info('Received SIGINT.');
  process.exit(130);  // Or applicable exit code depending on OS and signal
}); 拷贝

跟踪系统使用与 process.hrtime() 使用的时间源相同的时间源。然而，跟踪事件时间戳以微秒表示，与返回纳秒的 process.hrtime() 不同。

¥The tracing system uses the same time source as the one used by process.hrtime(). However the trace-event timestamps are expressed in microseconds, unlike process.hrtime() which returns nanoseconds.

此模块的功能在 Worker 线程中不可用。

¥The features from this module are not available in Worker threads.

const trace_events = require('node:trace_events');
const t1 = trace_events.createTracing({ categories: ['node', 'v8'] });
const t2 = trace_events.createTracing({ categories: ['node.perf', 'node'] });
t1.enable();
t2.enable();

// Prints 'node,node.perf,v8'
console.log(trace_events.getEnabledCategories());

t2.disable(); // Will only disable emission of the 'node.perf' category

// Prints 'node,v8'
console.log(trace_events.getEnabledCategories()); 拷贝

const trace_events = require('node:trace_events');
const categories = ['node.perf', 'node.async_hooks'];
const tracing = trace_events.createTracing({ categories });
tracing.enable();
// do stuff
tracing.disable(); 拷贝

const trace_events = require('node:trace_events');
const t1 = trace_events.createTracing({ categories: ['node.async_hooks'] });
const t2 = trace_events.createTracing({ categories: ['node.perf'] });
const t3 = trace_events.createTracing({ categories: ['v8'] });

t1.enable();
t2.enable();

console.log(trace_events.getEnabledCategories()); 拷贝

'use strict';

const { Session } = require('inspector');
const session = new Session();
session.connect();

function post(message, data) {
  return new Promise((resolve, reject) => {
    session.post(message, data, (err, result) => {
      if (err)
        reject(new Error(JSON.stringify(err)));
      else
        resolve(result);
    });
  });
}

async function collect() {
  const data = [];
  session.on('NodeTracing.dataCollected', (chunk) => data.push(chunk));
  session.on('NodeTracing.tracingComplete', () => {
    // done
  });
  const traceConfig = { includedCategories: ['v8'] };
  await post('NodeTracing.start', { traceConfig });
  // do something
  setTimeout(() => {
    post('NodeTracing.stop').then(() => {
      session.disconnect();
      console.log(data);
    });
  }, 1000);
}

collect(); 拷贝