Workbox

Maxim Salnikov

Angular GDE

Building an Angular PWA:

NGSW

?

- or -

How to create an Angular Progressive Web App?

Using the appropriate method

Maxim Salnikov

@webmaxru

Google Developer Expert in Angular
Angular Oslo / PWA Oslo meetups organizer
ngVikings / ngCommunity organizer

Azure Developer Technical Lead at Microsoft

What is PWA at all?

Progressive web apps use modern web APIs along with traditional progressive enhancement strategy to create cross-platform web applications.

https://developer.mozilla.org/en-US/Apps/Progressive

These apps work everywhere and provide several features that give them the same user experience advantages as native apps.

works everywhere*

* but not everything**

natively

** use progressive enhancement strategy

UX advantages?

Smart networking + Offline

Proper app experience

Staying notified

Other cool things

}

Service Worker API

Web App Manifest

Create Angular PWA

Code service worker manually
Use Angular Service Worker (NGSW)
Use some PWA libraries

sw-precache

Minimum viable PWA

=

+

Application shell

Web App Manifest

Fast, responsive, mobile-first

Served via HTTPS

Let's build an App shell

My App

Pick only the files we need
Create the list of files and their hashes
First load: put these files into the Cache Storage
Next loads: serve them from Cache Storage

If some files were updated (hashes comparison) put their new versions into the Cache Storage and remove old ones *
On the n+1 load - serve the updated files

The app was updated.

Refresh?

1

2

3 Service Worker 101

Logically

Physically

-file(s)

App

Service-worker

Browser/OS

Event-driven worker

Cache

fetch

push

sync

Managing cache

self.addEventListener('install', (event) => {
  
    // Put app's html/js/css to cache

})

self.addEventListener('activate', (event) => {
  
    // Wipe previous version of app files from cache

})

In the real world

Can't add opaque responses directly
Redirected requests should be managed
Always creating a new version of cache and deleting the old one is not optimal
Control over cache size is required
Cache invalidation for runtime caching is complex
...

Intercepting requests

self.addEventListener('fetch', (event) => {

  if (event.request.url.indexOf('/api') != -1) {
    event.respondWith(
      // Network-First Strategy
    )
  } else {
    event.respondWith(
      // Cache-First Strategy
    )
  }
})

In the real world

All kinds of fallbacks needed for the strategies
There are more complex strategies like Stale-While-Revalidate
Good to have routing
Good to have the possibility to provide some extra settings for different resource groups
...

Pros

Great flexibility!

Cons

Great responsibility!

Implementing complex algorithms
Adopting best practices
Focusing on YOUR task
Following specifications updates
Handling edge cases

Tools help with

NGSW

Angular Service Worker

NGSW

Automation

Scaffolding

Building

Serving

Schematics

Angular CLI

NGSW

$ ng add @angular/pwa

Scaffold

Add service worker registration code to the root module
Generate default service worker configuration file
Generate and link default Web App Manifest
Generate default icons set
Enable build support in Angular CLI config

$ ng build --prod

Build

ngsw.json

ngsw-worker.js

dist/project-name

1

2

Builds service worker manifest based on configuration file
Copies Angular Service Worker and safety workers

NGSW manifest

{
    "hashTable": {
        "/favicon.ico": "84161b857f5c547e3699ddffc6d8d",
        "/index.html": "64397c08d1f0da35f8e38e05c5512",
        ...
    },
    ...
}

ngsw-config.json / assetGroups

{
    "name": "app",
    "installMode": "prefetch",
    "resources":







}

    "resources": {    
        "files": [
            "/favicon.ico",
            "/index.html",
            "/*.css",
            "/*.js"
        ]
    }

Configuration file

https://angular.io/guide/service-worker-config

https://developers.google.com/web/tools/workbox/

Application shell
Runtime caching
Replaying failed network requests
Offline Google Analytics
Broadcasting updates

Have our own service worker!

Working modes

Workbox CLI
Webpack plugin
Node module

# Installing the Workbox Node module
$ npm install workbox-build --save-dev

Build script

// We will use injectManifest mode
const {injectManifest} = require('workbox-build')

// Sample configuration with the basic options
var workboxConfig = {...}

// Calling the method and output the result
injectManifest(workboxConfig).then(({count, size}) => {
    console.log(`Generated ${workboxConfig.swDest},
    which will precache ${count} files, ${size} bytes.`)
})

workbox-build-inject.js

Build script configuration

// Sample configuration with the basic options
var workboxConfig = {
  globDirectory: 'dist/angular-pwa/',
  globPatterns: [
    '**/*.{txt,png,ico,html,js,json,css}'
  ],
  swSrc: 'src/service-worker.js',
  swDest: 'dist/angular-pwa/service-worker.js'
}

workbox-build-inject.js

Source service worker

// Importing Workbox itself from Google CDN
importScripts('https://googleapis.com/.../workbox-sw.js');

// Precaching and setting up the routing
workbox.precaching.precacheAndRoute([])

src/service-worker.js

1

2

Workbox manifest

[
  {
    "url": "index.html",
    "revision": "34c45cdf166d266929f6b532a8e3869e"
  },
  {
    "url": "favicon.ico",
    "revision": "b9aa7c338693424aae99599bec875b5f"
  },
  ...
]

Build flow integration

{
  "scripts": {
    "build-prod": "ng build --prod &&
                   node workbox-build-inject.js"
  }
}

package.json

NGSW

Convenient build module
Having our own service worker and extending it by Workbox modules

One-liner to start
Seamless integration
Smart defaults

Better app update UX

App version updates

v1

v2

v1

v2

Deployed

Displayed

v2

A new version of the app is available. Click to refresh.

SwUpdate service

import { SwUpdate } from '@angular/service-worker';

constructor(updates: SwUpdate) {}

this.updates.available.subscribe(event => {




})

updates.component.ts

    if (confirm(`New Version is available! OK to refresh`)) {
            window.location.reload();
    }

3

Hint: Provide a version description

{
  "appData": {
    "changelog": "New version: Dinosaur pic was added!"
  }
}

let changelog = event.available.appData['changelog']
let message = `${changelog} Click to refresh.`

ngsw-config.json

updates.component.ts

New version: Dinosaur pic was added! Click to refresh.

const updateChannel = new BroadcastChannel('app-shell');

updateChannel.addEventListener('message', event => {
    // Inform about the new version & prompt to reload
});

Option #1: BroadcastChannel

updates.component.ts

workbox.precaching.addPlugins([
    new workbox.broadcastUpdate.Plugin('app-shell')
]);

src/service-worker.js

3

Option #2: workbox-window

import { Workbox } from 'workbox-window'

platformBrowserDynamic().bootstrapModule(AppModule)
  .then( () => {
    if ('serviceWorker' in navigator) {
      const wb = new Workbox('service-worker.js');
      // Event listeners...
      wb.register();
    }
  })

main.ts

$ npm install workbox-window

https://developers.google.com/web/tools/workbox/modules/workbox-window

Was service worker file updated?

wb.addEventListener('installed', event => {
  if (event.isUpdate) {
  // Show "Newer version is available. Refresh?" prompt
  } else {
  // Optionally: show "The app is offline-ready" toast
  }
});

main.ts

3

workbox.core.skipWaiting()
workbox.core.clientsClaim()

service-worker.js

Must have!

https://medium.com/@webmaxru/workbox-4-implementing-refresh-to-update-version-flow-using-the-workbox-window-module-41284967e79c

NGSW

Possibility to use broadcastUpdate plugin also for receiving runtime caching updates

Angular-style coding: services, DI, observables
Passing version info to display in the notification

Runtime caching

Configuring strategies

ngsw-config.json / dataGroups

{
    "name": "api-freshness",
    "urls": [
      "/api/breakingnews/**"
    ],






}

    "cacheConfig": {
      "strategy": "freshness",
      "maxSize": 10,
      "maxAge": "12h",
      "timeout": "10s"
    }

Configuring strategies

{
    "name": "api-performance",
    "urls": [
      "/api/archive/**"
    ],






}

    "cacheConfig": {
      "strategy": "performance",
      "maxSize": 100,
      "maxAge": "365d"
    }

ngsw-config.json / dataGroups

Hint: Support API versioning

{
    "version": 1,
    "name": "api-performance",
    "urls": [
      "/api/**"
    ],
    ...
}

{
    "version": 2,
    "name": "api-performance",
    "urls": [
      "/api/**"
    ],
    ...
}

ngsw-config.json / dataGroups

Strategies and plugins

workbox.routing.registerRoute(
  new RegExp('/app/v2/'),
  workbox.strategies.networkFirst()
);

src/service-worker.js

workbox.routing.registerRoute(
  new RegExp('/images/'),
  workbox.strategies.cacheFirst({
    plugins: [...]
  })
);

Strategies

CacheFirst
CacheOnly
NetworkFirst
NetworkOnly
StaleWhileRevalidate

Plugins

Expiration
CacheableResponse
BroadcastUpdate
BackgroundSync
...your own plugin?

NGSW

Variety of strategies
Maximum flexible configuration including adding own logic via the plugins

Code-free configuration of two strategies
Runtime cache versioning

Summary

NGSW

Easy to start
Seamless integration with Angular
Coding-free basic features
Angular-friendly approach

Add -> Configure

Get what's included

Framework-agnostic
Rich functionality
Maximum flexible configuration
Full power of our own service worker

Setup -> Configure -> Code

Get what you want

2000+ developers
Major browsers/frameworks/libs reps

bit.ly/go-pwa-slack

Thank you!

Maxim Salnikov

@webmaxru

Questions?

Maxim Salnikov

@webmaxru

Workbox

Building an Angular PWA:

NGSW

?

?

?

- or -

How to create an Angular Progressive Web App?

Using the appropriate method

Maxim Salnikov

@webmaxru

Google Developer Expert in Angular

Angular Oslo / PWA Oslo meetups organizer

ngVikings / ngCommunity organizer

What is PWA at all?

These apps work everywhere and provide several features that give them the same user experience advantages as native apps.

works everywhere*

natively

UX advantages?

Smart networking + Offline

Proper app experience

Staying notified

Other cool things

}

Create Angular PWA

Code service worker manually

Use Angular Service Worker (NGSW)

Use some PWA libraries

sw-precache

Minimum viable PWA

=

+

Application shell

Web App Manifest

Fast, responsive, mobile-first

Served via HTTPS

Let's build an App shell

Pick only the files we need

Create the list of files and their hashes

First load: put these files into the Cache Storage

Next loads: serve them from Cache Storage

If some files were updated (hashes comparison) put their new versions into the Cache Storage and remove old ones *

On the n+1 load - serve the updated files

1

2

3

Service Worker 101

Logically

Physically

-file(s)

Managing cache

In the real world

Can't add opaque responses directly

Redirected requests should be managed

Always creating a new version of cache and deleting the old one is not optimal

Control over cache size is required

Cache invalidation for runtime caching is complex

...

Intercepting requests

In the real world

All kinds of fallbacks needed for the strategies

There are more complex strategies like Stale-While-Revalidate

Good to have routing

Good to have the possibility to provide some extra settings for different resource groups

...

Pros

Great flexibility!

Cons

Great responsibility!

Implementing complex algorithms

Adopting best practices

Focusing on YOUR task

Following specifications updates

Handling edge cases

Tools help with

NGSW

Angular Service Worker

NGSW

Automation

Scaffolding