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Merge pull request #32 from Financial-Times/perfume
Use Perfume.js for Real User Monitoring of Performance Metrics
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119 changes: 70 additions & 49 deletions
119
src/client/trackers/real-user-monitoring-for-performance.js
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,60 +1,81 @@ | ||
| import ttiPolyfill from 'tti-polyfill'; | ||
| import Perfume from 'perfume.js'; | ||
| import { broadcast } from '../broadcast'; | ||
| import { userIsInCohort } from '../utils/userIsInCohort'; | ||
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| // Perfume.js is a web performance package. | ||
| // @see https://zizzamia.github.io/perfume/#/default-options/ | ||
| const options = { | ||
| logging: false, | ||
| firstPaint: true, | ||
| largestContentfulPaint: true, | ||
| firstInputDelay: true, | ||
| largestContentfulPaint: true, | ||
| navigationTiming: true, | ||
| }; | ||
|
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| // @see "Important metrics to measure" https://web.dev/metrics | ||
| const requiredMetrics = [ | ||
| 'domInteractive', | ||
| 'domComplete', | ||
| 'timeToFirstByte', | ||
| 'firstPaint', | ||
| 'largestContentfulPaint', | ||
| 'firstInputDelay' | ||
| ]; | ||
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| const cohortPercent = 5; | ||
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| export const realUserMonitoringForPerformance = () => { | ||
| const cohortPercent = 5; | ||
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| // Check browser support. | ||
| // @see https://developer.mozilla.org/en-US/docs/Web/API/PerformanceLongTaskTiming | ||
| if (!'PerformanceLongTaskTiming' in window) return; | ||
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| // Gather metrics for only a cohort of users. | ||
| if (!userIsInCohort(cohortPercent)) return; | ||
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| // For browser compatibility @see: https://mdn.github.io/dom-examples/performance-apis/perf-api-support.html | ||
| if (!'PerformanceLongTaskTiming' in window || !'ttiPolyfill' in window) return; | ||
| const navigation = performance.getEntriesByType('navigation')[0]; | ||
| const { type, domInteractive, domComplete } = navigation; | ||
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| // @see: https://web.dev/lcp/#how-to-measure-lcp (largest-contentful-paint) | ||
| let largestContentfulPaint; | ||
| const lcpPerformanceObserver = new PerformanceObserver((entryList) => { | ||
| const entries = entryList.getEntries(); | ||
| const lastEntry = entries[entries.length - 1]; | ||
| largestContentfulPaint = lastEntry.renderTime || lastEntry.loadTime; | ||
| }); | ||
| lcpPerformanceObserver.observe({type: 'largest-contentful-paint', buffered: true}); | ||
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| ttiPolyfill.getFirstConsistentlyInteractive().then(timeToInteractive => { | ||
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| // Disconnect the observer once it no longer needs to observe the performance data | ||
| // @SEE: https://w3c.github.io/performance-timeline/#the-performanceobserver-interface | ||
| lcpPerformanceObserver.disconnect(); | ||
|
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| const navigation = performance.getEntriesByType('navigation')[0]; | ||
| const { type, domInteractive, domComplete, responseStart, requestStart } = navigation; | ||
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| // Proceed only if the page load event is a "navigate". | ||
| // @see: https://developer.mozilla.org/en-US/docs/Web/API/PerformanceNavigationTiming/type | ||
| if (type !== 'navigate') return; | ||
|
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| try { | ||
| const timeToFirstByte = responseStart - requestStart; | ||
| const firstPaint = performance.getEntriesByName('first-paint')[0].startTime; | ||
| const firstContentfulPaint = performance.getEntriesByName('first-contentful-paint')[0].startTime; | ||
| const context = { | ||
| firstPaint: Math.round(firstPaint), | ||
| firstContentfulPaint: Math.round(firstContentfulPaint), | ||
| timeToFirstByte: Math.round(timeToFirstByte), | ||
| domInteractive: Math.round(domInteractive), | ||
| domComplete: Math.round(domComplete), | ||
| largestContentfulPaint: Math.round(largestContentfulPaint), | ||
| timeToInteractive: Math.round(timeToInteractive), | ||
| }; | ||
|
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| console.log(context); // eslint-disable-line no-console | ||
| const data = { | ||
| action: 'performance', | ||
| category: 'page', | ||
| ...context | ||
| }; | ||
| broadcast('oTracking.event', data); | ||
| // Proceed only if the page load event is a "navigate". | ||
| // @see: https://developer.mozilla.org/en-US/docs/Web/API/PerformanceNavigationTiming/type | ||
| if (type !== 'navigate') return; | ||
|
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| const context = { | ||
| action: 'performance', | ||
| category: 'page', | ||
| domInteractive: Math.round(domInteractive), | ||
| domComplete: Math.round(domComplete), | ||
| }; | ||
|
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| /** | ||
| * analyticsTracker() | ||
| * | ||
| * This function is called every time one of the performance events occurs. | ||
| * The "final" event should be `firstInputDelay`, which is triggered by any "input" event (most likely to be a click.) | ||
| * Once all the metrics are present, it fires a broadcast() to the Spoor API. | ||
| */ | ||
| let hasAlreadyBroadcast = false; | ||
| options.analyticsTracker = (({ metricName, duration, data }) => { | ||
| if (hasAlreadyBroadcast) return; | ||
|
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| if (duration) { | ||
| // Metrics with "duration": | ||
| // firstPaint, firstContentfulPaint, firstInputDelay and largestContentfulPaint | ||
| context[metricName] = Math.round(duration); | ||
| } | ||
| catch (error) { | ||
| console.error(error); // eslint-disable-line no-console | ||
| else if (metricName === 'navigationTiming') { | ||
| context.timeToFirstByte = Math.round(data.timeToFirstByte); | ||
| } | ||
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| // Broadcast only if all the metrics are present | ||
| const contextContainsAllRequiredMetrics = requiredMetrics.every(metric => !isNaN(context[metric])); | ||
| if (contextContainsAllRequiredMetrics) { | ||
| console.log({performanceMetrics:context}); // eslint-disable-line no-console | ||
| broadcast('oTracking.event', context); | ||
| hasAlreadyBroadcast = true; | ||
| } | ||
| }); | ||
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| new Perfume(options); | ||
| }; |