146 lines
3.1 KiB
JavaScript
146 lines
3.1 KiB
JavaScript
import path from 'path'
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import fs from 'fs'
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let inspector
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try {
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inspector = require('inspector')
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} catch (e) {
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console.log('Unable to CPU profile in < node 8.0')
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}
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class Profiler {
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constructor(inspector) {
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this.session = undefined
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this.inspector = inspector
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}
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hasSession() {
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return this.session !== undefined
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}
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startProfiling() {
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if (this.inspector === undefined) {
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return Promise.resolve()
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}
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try {
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this.session = new inspector.Session()
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this.session.connect()
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} catch (_) {
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this.session = undefined
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return Promise.resolve()
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}
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return Promise.all([
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this.sendCommand('Profiler.setSamplingInterval', {
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interval: 100,
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}),
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this.sendCommand('Profiler.enable'),
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this.sendCommand('Profiler.start'),
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])
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}
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sendCommand(method, params) {
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if (this.hasSession()) {
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return new Promise((resolve, reject) => {
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return this.session.post(method, params, (err, params) => {
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if (err !== null) {
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reject(err)
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} else {
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resolve(params)
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}
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})
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})
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} else {
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return Promise.resolve()
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}
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}
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destroy() {
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if (this.hasSession()) {
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this.session.disconnect()
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}
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return Promise.resolve()
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}
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stopProfiling() {
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return this.sendCommand('Profiler.stop')
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}
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}
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const { Tracer } = require('chrome-trace-event')
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/**
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* an object that wraps Tracer and Profiler with a counter
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* @typedef {Object} Trace
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* @property {Tracer} trace instance of Tracer
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* @property {number} counter Counter
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* @property {Profiler} profiler instance of Profiler
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* @property {Function} end the end function
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*/
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/**
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* @param {string} outputPath The location where to write the log.
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* @returns {Trace} The trace object
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*/
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export const createTrace = (outputPath) => {
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const trace = new Tracer({
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noStream: true,
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})
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const profiler = new Profiler(inspector)
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if (/\/|\\/.test(outputPath)) {
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const dirPath = path.dirname(outputPath)
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fs.mkdirSync(dirPath, { recursive: true })
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}
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const fsStream = fs.createWriteStream(outputPath)
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let counter = 0
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trace.pipe(fsStream)
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// These are critical events that need to be inserted so that tools like
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// chrome dev tools can load the profile.
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trace.instantEvent({
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name: 'TracingStartedInPage',
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id: ++counter,
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cat: ['disabled-by-default-devtools.timeline'],
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args: {
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data: {
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sessionId: '-1',
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page: '0xfff',
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frames: [
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{
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frame: '0xfff',
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url: 'webpack',
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name: '',
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},
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],
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},
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},
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})
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trace.instantEvent({
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name: 'TracingStartedInBrowser',
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id: ++counter,
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cat: ['disabled-by-default-devtools.timeline'],
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args: {
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data: {
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sessionId: '-1',
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},
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},
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})
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return {
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trace,
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counter,
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profiler,
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end: (callback) => {
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// Wait until the write stream finishes.
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fsStream.on('finish', () => {
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callback()
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})
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// Tear down the readable trace stream.
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trace.push(null)
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},
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}
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}
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