Web performance optimisation for single page applications

Accompanying slides to a 4 hour course on monitoring and web performance optimisation for single page applications

Transcript

1. WPO for SPAs The epic battle against loading indicators
2. Stefan Baumgartner Internet Batman Larry Urbano Senior Sales Engineer Monitoring redefined
3. Agenda 1. Some theory 2.We meet our Single Page Application 3.Performance optimisation techniques 4.Some live coding and lots of demos
4. Title Text Breaks
5. Subheadline
6. Why have we moved to SPAs?
7. Client Client Initial request HTML payload Form POST HTML payload Traditional
8. Client Client Initial request HTML payload AJAX call via JS HTML Diff SPA
9. Single Page Applications are awesome … ▪ They provide better UX once loaded ▪ Communication is reduced to deltas ▪ This results in fewer requests and smaller payload ▪ Should your Network die, you still have some content available ▪ They’re super-easy to deploy
10. Single Page Applications are hard… ▪ The client is in control… but the client starts when everything has been transferred ▪ The client side app has to take care of all the errors and has to be a lot lot smarter ▪ Flaky networks harm the UX ▪ Fallbacks are hard ▪ Bad practices are more seductive ▪ States are hard to share
11. Client Client Initial request non-content HTML AJAX call via JS content diff SPAs Resource request JavaScript payload Initial AJAX call via JS content payload
12. Client Client Initial request non-content HTML AJAX call via JS content diff SPAs Resource request JavaScript payload Initial AJAX call via JS content payload What is going on here?
14. Subheadline
15. initial HTML request angular.js main.js data/from/backend
16. All of them?
17. prompt for unload redirect DNS TCP Request Response Processing onLoad navigationStart redirectStart redirectEnd domainLookupStart domainLookupEnd connectStart connectEnd requestStart responseStart responseEnd domLoading domInteractive domContentLoaded domComplete loadEventStart loadEventEnd
18. prompt for unload redirect DNS TCP Request Response Processing onLoad navigationStart redirectStart redirectEnd domainLookupStart domainLookupEnd connectStart connectEnd requestStart responseStart responseEnd domLoading domInteractive domContentLoaded domComplete loadEventStart loadEventEnd
19. domLoading domInteractive domContentLoaded domComplete
20. domLoading domInteractive domContentLoaded domComplete The DOM is getting parsed DOM is parsed and ready to work on The document is loaded (wo stylesheets, images) All sub resources are loaded
21. Let’s check our SPA Demo-time
23. cd /app/twitterwall-server npm start service nginx start
24. cd /app/twitterwall-client-webpack (commands to follow)
25. replace contents of /app/twitterwall-server/public with /app/twitterwall-client-webpack/dist
26. npm stop npm start
27. Step 1: Production builds Put back your development pride
28. CSS JS
29. CSS JS
30. CSS JS VENDOR
31. CSS JS VENDOR
32. Step 2: Tree shaking It’s not as funny as it sounds. But equally cool
33. ESnext module syntax ▪ EcmaScript finally has a module syntax (and probably a module loading strategy soon as well!) ▪ Tooling allows us to use this new syntax already import { createServer } from ‘http’; import * as path from ‘path’; export function cube(x) { return x*x*x; } export default { … } const createServer = require(‘http’).createServer; const path = require(‘path’); module.exports = { cube: function(x) { return x*x*x} }
34. Tree Shaking ▪ This new syntax allows tools to do a static code analysis based on the JavaScript AST. ▪ With that, we can exclude functions we simply do not need, reducing our bundle size even more.
35. Angular Ahead of Time compilation ▪ Faster rendering: With AOT, the browser downloads a pre-compiled version of the application. The browser loads executable code so it can render the application immediately, without waiting to compile the app first. ▪ Fewer asynchronous requests: The compiler inlines external html templates and css style sheets within the application JavaScript, eliminating separate ajax requests for those source files.
36. Angular Ahead of Time compilation ▪ Smaller Angular framework download size: There’s no need to download the Angular compiler if the app is already compiled. The compiler is roughly half of Angular itself, so omitting it dramatically reduces the application payload. ▪ Detect template errors earlier: The AOT compiler detects and reports template binding errors during the build step before users can see them. ▪ Better security: AOT compiles HTML templates and components into JavaScript files long before they are served to the client. With no templates to read and no risky client-side HTML or JavaScript evaluation, there are fewer opportunities for injection attacks
37. Step 3: SSR Putting the server back into the equation
38. initial HTML request angular.js main.js data/from/backend Start render
39. initial HTML request angular.js main.js data/from/backend Start render?
40. The network is a bottle-neck
41. So make every request count!
42. Client Client Initial request non-content HTML AJAX call via JS content diff Resource request JavaScript payload Initial AJAX call via JS content payload App
43. Client Client Initial request Initial Render HTML AJAX call via JS content diff Resource request JavaScript payload Initial AJAX call via JS content payload App App
44. Important content first Everything else is an enhancement
45. Server side rendering for SPAs ▪ Thanks to a little technology called Node.js, we are able to render JS on the client and the server ▪ As long as you have valid routes (= URLs), you have the ability to render the state on the server ▪ The first requests bring the rendered state ▪ Then the JavaScript framework kicks in
49. But I can’t move all by backend to Node.js
50. You don’t have to!
52. Bonus round! Lazy loaded routes
53. Bundling … ▪ Why bundle everything, when we just need a few things to start? ▪ Routes deep down in the navigation might not be used at all… ▪ Bundle by routes, split away code that you don’t need at first…
54. Bonus round! Responsive images
55. <img src=”screenshot-600.png” srcset="screenshot-200.png 200w, screenshot-400.png 400w, screenshot-600.png 600w, screenshot-800.png 800w, screenshot-1000.png 1000w, screenshot-1200.png 1200w, screenshot-1400.png 1400w, screenshot-1600.png 1600w” sizes="(min-width: 900px) 50vw, 100vw" alt=”Super screenshot of our product.">
56. <img src=”screenshot-600.png” srcset="screenshot-200.png 200w, screenshot-400.png 400w, screenshot-600.png 600w, screenshot-800.png 800w, screenshot-1000.png 1000w, screenshot-1200.png 1200w, screenshot-1400.png 1400w, screenshot-1600.png 1600w” sizes="(min-width: 900px) 50vw, 100vw" alt=”Super screenshot of our product."> A low-res fallback image for browsers that don’t know srcset These sources are available. For each “width unit” there’s a reduced version of our original screenshot The sizes define which source to choose from. Retina screens are also checked
57. s Subheadline Speed Index
60. ∫ 1 - visuallycomplete/100 0 end
61. What does this mean?
66. Visually complete (%) 0 25 50 75 100 Time in Seconds 0s 1s 2s 3s 4s 5s 6s 7s 8s
67. Visually complete (%) 0 25 50 75 100 Time in Seconds 0s 1s 2s 3s 4s 5s 6s 7s 8s
68. Visually complete (%) 0 25 50 75 100 Time in Seconds 0s 1s 2s 3s 4s 5s 6s 7s 8s
69. s Subheadline Thoughts about HTTP2
70. Server Client HTTP/2 Getting stuff … GET image1 image1 header image1 payload image1 payload image2 header image2 payload image1 payload image2 payload GET image2
71. HTTP 1.1 index.html a.js b.js c.js d.js
72. HTTP 2 index.html a.js b.js c.js d.js
73. HTTP 2 index.html a.js b.js c.js d.js
74. HTTP 2 index.html a.js b.js c.js d.js
76. Desktop HTTP/2 ~1.8s HTTP1.1 ~2.6s
77. mobile connections HTTP1.1 ~3.37s HTTP2 ~1.72
78. A slow website on HTTP1.1 will still be a slow website on HTTP2
79. Frequency of change Libraries Utilities Module Module Module Module rigid high frequency some frequency
80. Optimised utility layer Libraries Utilities Module Module Module rigid high frequency some frequency
81. Extending the utility layer Libraries Utilities Module Module Module rigid high frequency some frequency
82. Files to change Libraries Utilities Module Module Module rigid high frequency some frequency
83. Frequency of change Libraries Module Module Module rigid high frequency Module
84. What to do with your application?
85. The best request is a request not being made
86. Create independent, exchangeable components
87. Create small, detached bundles
88. Code duplication and weight is okay if the file can stay longer
89. Think about long lasting applications and frequency of change
90. Thank you.