Angular Performance: Your App at the Speed of Light

What doesn't load in two seconds will never be accessed again: User expectations for web application performance are steadily increasing. After a web application loads, it needs to feel fast and fluid in order for the user to achieve their goal. In our Thinktecture webinar, Christian Liebel will show you Angular’s most important optimization options (Zone.js, Change Detection and Service Workers), so that you can ignite the turbo for your Angular app!

Transcript

1. Angular Performance Your App at the Speed of Light Christian Liebel @christianliebel Consultant
2. Angular Performance Your App at the Speed of Light Agenda Change Detection & NgZone Change Detection Strategies Lazy Loading Service Workers
3. Angular Performance Your App at the Speed of Light Agenda Change Detection & NgZone Change Detection Strategies Lazy Loading Service Workers
4. Reduce required computations during runtime - calculations - painting - layouting - detecting changes Angular Performance Your App at the Speed of Light Runtime Performance
5. Hi Angular! Basics // app.component.html <h1>Hi {{ title }}!</h1> // app.component.ts @Component({ /* … */ }) export class AppComponent { title = 'Angular'; } Angular Performance Your App at the Speed of Light Change Detection
6. Basics // app.component.html <h1>Hi {{ title }}!</h1> <button (click)="update()"> Update </button> // app.component.ts @Component({ /* … */ }) export class AppComponent { title = 'Angular'; update() { this.title = 'Foo'; } } Angular Performance Your App at the Speed of Light Change Detection Hi Foo! Hi Angular! Update
7. Component Tree AppComponent NavComponent ContentComponent ListComponent Angular Performance Your App at the Speed of Light Change Detection
8. Change Detector Tree AppComponent NavComponent ContentComponent ListComponent Angular Performance Your App at the Speed of Light Change Detection AppComponent CD NavComponent CD ContentComponent CD ListComponent CD CHANGE
9. Per default, each change in your application leads to… - A single CD cycle - From top to bottom (all components) - Unidirectional (no cycles allowed) Angular Performance Your App at the Speed of Light Change Detection DEMO
10. Findings Reduce duration of a change detection cycle - Reduce amount of bindings (e.g. grids: virtual scrolling via CDK) - Avoid binding to (computationally intensive) getters or functions Keep CD cycle < 16 ms! Angular Performance Your App at the Speed of Light Change Detection
11. Profiling // main.ts platformBrowserDynamic().bootstrapModule(AppModule).then(module => enableDebugTools(module.injector.get(ApplicationRef).components[0])); Execute ng.profiler.timeChangeDetection() to measure the duration of a change detection run (500ms or 5 change detection cycles) Angular Performance Your App at the Speed of Light Change Detection DEMO
12. How to detect a change? AppComponent NavComponent ContentComponent ListComponent Angular Performance Your App at the Speed of Light Zone.js AppComponent CD NavComponent CD ContentComponent CD ListComponent CD CHANGE
13. A look at Angular’s dependencies "dependencies": { "@angular/common": "~11.2.0", "rxjs": "~6.6.0", "tslib": "^2.0.0", "zone.js": "~0.10.2" }, Zone.js Your App at the Speed of Light Angular Performance
14. Overview Provided by the Angular team Open-source https://github.com/angular/zone.js 1. Provides an execution context for asynchronous JavaScript 2. A meta-monkey patch Zone.js Your App at the Speed of Light Angular Performance
15. Execution Context Oversimplified Zone.run(main); onZoneEnter(); function main() { a(); setTimeout(b, 0); c(); } onZoneLeave(); Zone.js const orig = window.setTimeout; window.setTimeout = (c, t) => { orig(() => { onZoneEnter(); c(); onZoneLeave(); }, t); }; Your App at the Speed of Light Angular Performance
16. A Meta-Monkey Patch Zone.js setTimeout setInterval geolocation.getCurrentPosition XMLHttpRequest PromiseRejectionEvent requestAnimationFrame click focus mousemove addEventListener Your App at the Speed of Light Angular Performance
17. NgZone Angular Performance Your App at the Speed of Light Zone.js current (global) zone NgZone Angular boot
18. NgZone NgZone catches asynchronous operations from the Angular app When no tasks are remaining for the current VM turn, the NgZone will trigger a change detection cycle (tick) Angular Performance Your App at the Speed of Light Zone.js NgZone setTimeout setInterval onclick Detect changes Detect changes Detect changes
19. Change Detection Trigger https://github.com/angular/angular/blob/master/packages/core/src/application_ref.ts Angular Performance Your App at the Speed of Light Zone.js NgZone.onMicrotaskEmpty ApplicationRef.tick() view1.detectChanges() view2.detectChanges() viewN.detectChanges()
20. Common Pitfalls Long CD cycles in combination with high-frequency events - mousemove - scroll - requestAnimationFrame - setInterval with short intervals (clocks!) Angular Performance Your App at the Speed of Light Zone.js DEMO
21. NgZone Zone.js current (global) zone NgZone rAF Detect changes rAF Detect changes rAF Detect changes rAF Detect changes Your App at the Speed of Light Angular Performance
22. NgZone Opt-Out constructor (ngZone: NgZone) { ngZone.runOutsideAngular(() => { // runs outside Angular zone, for performance-critical code ngZone.run(() => { // runs inside Angular zone, for updating view afterwards }); }); } Zone.js Your App at the Speed of Light Angular Performance ! View and model can get out of sync! DEMO
23. NgZone Zone.js current (global) zone NgZone rAF rAF rAF rAF Your App at the Speed of Light Angular Performance
24. Disable Patches (polyfills.ts) (window as any).__Zone_disable_requestAnimationFrame = true; // disable patch requestAnimationFrame (window as any).__Zone_disable_on_property = true; // disable patch onProperty such as onclick (window as any).__zone_symbol__UNPATCHED_EVENTS = ['scroll', 'mousemove']; // disable patch specified eventNames Angular Performance Your App at the Speed of Light Zone.js ! View and model can get out of sync!
25. Event Coalescing <div (click)="doSomething()"> <button (click)="doSomethingElse()">Test</button> </div> // main.ts platformBrowserDynamic().bootstrapModule(AppModule, { ngZoneEventCoalescing: true }); Angular Performance Your App at the Speed of Light Zone.js ! App behavior may change! CHANGE CHANGE Coalescing
26. Disable Zone (= disable async change detection!) platformBrowserDynamic().bootstrapModule(AppModule, { ngZone: 'noop' }); constructor(applicationRef: ApplicationRef) { applicationRef.tick(); // trigger CD yourself } Angular Performance Your App at the Speed of Light Zone.js ! View and model can get out of sync!
27. Angular Performance Your App at the Speed of Light Agenda Change Detection & NgZone Change Detection Strategies Lazy Loading Service Workers
28. Overview Default Uses Zone.js for detecting changes and updates bindings OnPush Restricts change detection to changes of @Input parameters Angular Performance Your App at the Speed of Light Change Detection Strategies AppComponent CD NavComponent CD ContentComponent CD ListComponent CD AppComponent CD NavComponent CD ContentComponent CD ListComponent CD OnPush
29. OnPush <my-component [foo]="bar"> </my-component> @Component({ selector: 'my-component', template: '{{ foo }}', changeDetection: ChangeDetectionStrategy.OnPush }) export class MyComponent { @Input() public foo: string; } Change detection only reacts to events within the component and changes of @Input() parameters Angular compares the values passed to an @Input() via Object.is(oldValue, newValue) If you are passing objects, make sure to pass in new instances! Angular Performance Your App at the Speed of Light Change Detection Strategies ! View and model can get out of sync!
30. // app.component.ts @Component({ changeDetection: ChangeDetectionStrategy.OnPush }) /* … */ ngOnInit() { requestAnimationFrame(() => this.ngOnInit()); // this._ngZone.runOutsideAngular(() => request…); } Angular Performance Your App at the Speed of Light Change Detection Strategies DEMO
31. OnPush & Detecting Changes What to do if a component changes unrelated to an @Input parameter? constructor(private dataService: DataService) {} ngOnInit() { this.dataService.updates$ .subscribe(newData => this.data = newData); // no update! } Angular Performance Your App at the Speed of Light Change Detector
32. markForCheck() Explicitly marks a component as dirty/changed (when using OnPush) Angular Performance Your App at the Speed of Light Change Detector AppComponent CD NavComponent CD ContentComponent CD ListComponent CD DIRTY AppComponent CD NavComponent CD ContentComponent CD ListComponent CD OnPush
33. markForCheck() constructor(private dataService: DataService, private cdRef: ChangeDetectorRef) {} ngOnInit() { this.dataService.updates$.subscribe(newData => { this.data = newData; this.cdRef.markForCheck(); }); } Angular Performance Your App at the Speed of Light Change Detector
34. Overview Takes observables, promises or synchronous values {{ data$ | async }} Waits for the observable to emit/promise to resolve and then displays the value Angular Performance Your App at the Speed of Light Async Pipe
35. Advantages For observables: - Async Pipe subscribes for you - Async Pipe takes care of unsubscribing from the observable - Async Pipe calls markForCheck() for each update – perfect match for OnPush! https://github.com/angular/angular/blob/master/packages/common/src/pipes/async_pipe.ts Angular Performance Your App at the Speed of Light Async Pipe
36. Simplifying OnPush constructor(private dataService: DataService, private cdRef: ChangeDetectorRef) {} ngOnInit() { this.dataService.updates$.subscribe(newData => { this.data = newData; this.cdRef.markForCheck(); }); } Angular Performance Your App at the Speed of Light Async Pipe
37. Simplifying OnPush // component.ts data$: Observable<string>; constructor(dataService: DataService) { this.data$ = this.dataService.updates$; } // component.html {{ data$ | async }} Angular Performance Your App at the Speed of Light Async Pipe DEMO
38. Detaching Components changeDetector.detach(); changeDetector.reattach(); Angular Performance Your App at the Speed of Light Change Detector AppComponent CD NavComponent CD ContentComponent CD ListComponent CD AppComponent CD NavComponent CD ContentComponent CD ListComponent CD ! View and model can get out of sync!
39. Findings Reduce amount of change detection cycles - Disable Zone.js (not a good idea in most cases) - Coalesce CD cycles (might change behavior of existing apps) - Opt-out of NgZone (for operations that should not affect bindings) - Disable Zone.js patches (in case you can’t opt-out, e.g. 3rd party libs) - ChangeDetectionStrategy.OnPush (good default, but be careful) - Local change detection via ChangeDetectorRef (for the few components that do not have to respond to changes from outside) Angular Performance Your App at the Speed of Light Change Detector
40. - Reduce initial load (size & computation) - Reduce perceived loading time - Prevent downloading the same resource again Angular Performance Your App at the Speed of Light Load Time Performance
41. Angular Performance Your App at the Speed of Light Agenda Change Detection & NgZone Change Detection Strategies Lazy Loading Service Workers
42. Overview Angular router supports lazy loading components transparently Lazy loaded components are not delivered to/loaded by the client on boot, but on purpose Reduces load & perceived loading time Lazy Loading Your App at the Speed of Light Angular Performance
43. Architecture Lazy Loading is module-based Module is resolved via a dynamic import: import('./feature.module').then(m => m.FeatureModule) Routing is delegated to the feature module called Lazy Loading Your App at the Speed of Light Angular Performance
44. Overview const ROUTES: Routes = [{ path: 'admin', loadChildren: () => import('app/admin/admin.module') .then(a => a.AdminModule) }]; Lazy Loading Your App at the Speed of Light Angular Performance DEMO
45. Configuring Lazy Loading NoPreloading - does not preload any route by default - advantage: low size footprint - disadvantage: takes some time after clicking a link to the lazy-loaded module, not offline capable PreloadAllModules - automatically preloads all modules after the application has launched (still better loading time!) - advantage: lazy-loaded modules now load instant (also on the first click), offline capable - disadvantage: higher footprint Angular Performance Your App at the Speed of Light Preloading Strategies
46. Unrelated To Routes Angular CLI generates bundles for all import()s and transparently downloads them when the function is invoked. function onClick() { import('./heavy-bundle').then(bundle => bundle.compute()); } Angular Performance Your App at the Speed of Light Lazy Loading
47. Angular Performance Your App at the Speed of Light Agenda Change Detection & NgZone Change Detection Strategies Lazy Loading Service Workers
48. Idea: Never load the same resource twice Download resources once and store them in a local cache The next time the user wants to open the application, load the contents from there Makes your application sources offline-capable Significantly improves loading time Angular Performance Your App at the Speed of Light Service Worker
49. Key Technology Service Worker Service Worker Internet Website HTML/JS Cache fetch Your App at the Speed of Light Angular Performance
50. Commands ng add @angular/pwa ng build --prod cd dist/perf-demo npx lite-server Service Worker Your App at the Speed of Light Angular Performance DEMO
51. Findings – Prevent downloading the same resource twice by using the Service Worker – Postpone loading less frequently used parts of your application by leveraging lazy loading Angular Performance Your App at the Speed of Light Load-Time Performance
52. Thank you for your kind attention! Christian Liebel @christianliebel christian.liebel@thinktecture.com