Service worker – update cache on new version using skipWaiting()

I have implemented Workbox to generate my service worker using webpack. This works – I can confirm revision is updated in the generated service worker when running "generate-sw": "workbox inject:manifest".

The problem is – I have noticed my clients are not updating the cache after a new release. Even days after updating the service worker my clients are still caching the old code and new code will only load after several refreshes and/or unregistering the service worker. For each release I have confirmed that the revision is updated.

I understand that I need to implement skipWaiting to ensure the clients gets updated – especially PWA. I have read, and tried to follow the 3rd approach here: https://redfin.engineering/how-to-fix-the-refresh-button-when-using-service-workers-a8e27af6df68.

My app mounts in app.js

I have added this code to serviceWorker-base.js

addEventListener('message', function(messageEvent){
  if (messageEvent.data === 'skipWaiting') return skipWaiting();
});

I have this code in app.js

const runServiceWorker = true
const serviceWorkerAvailable = ('serviceWorker' in navigator) ? true : false

// reload once when the new Service Worker starts activating
let refreshing
navigator.serviceWorker.addEventListener('controllerchange', function() {
    if (refreshing) return
    refreshing = true
    window.location.reload()
  }
)

function promptUserToRefresh(reg) {
  // this is just an example - don't use window.confirm in real life; it's terrible
  if (window.confirm("New version available! OK to refresh?")) {
    reg.waiting.postMessage('skipWaiting')
  }
}

function listenForWaitingServiceWorker(reg, callback) {
  console.log('listenForWaitingServiceWorker')
  function awaitStateChange() {
    reg.installing.addEventListener('statechange', function() {
      if (this.state === 'installed') callback(reg)
    })
  }
  if (!reg) return
  if (reg.waiting) return callback(reg)
  if (reg.installing) awaitStateChange()
  reg.addEventListener('updatefound', awaitStateChange)
}

// Register service worker
if (runServiceWorker && serviceWorkerAvailable) {
  navigator.serviceWorker.register('/serviceWorker.js')
  .then( (registration) => {
    console.log('Service worker registered', registration)
    listenForWaitingServiceWorker(registration, promptUserToRefresh) // <-- Added to existing code
  })
}else{
  console.log('Service worker disabled - process.env.NODE_ENV', process.env.NODE_ENV)
}

The problem with this code is that promptUserToRefresh() only gets called on initial service worker install, not when a new service worker is waiting!

Also, I get the below error when accepting the first install.

TypeError: registration.waiting is null
promptUserToRefresh app.js:154
awaitStateChange app.js:162

The error gets triggered in promptUserToRefresh(registration) by registration.waiting.postMessage('skipWaiting')

I have also tested this approach with the same result: https://github.com/GoogleChrome/workbox/issues/1120

Answer

The code now works after simply re-arranging it!

Updated app.js

// *** PWA Functionality START ***

// skipWaiting() functions
function promptUserToRefresh(registration) {
  // this is just an example - don't use window.confirm in real life; it's terrible
  if (window.confirm("New version available! Refresh?")) {
    registration.waiting.postMessage('skipWaiting')
  }
}
function listenForWaitingServiceWorker(registration) {
  console.log('listenForWaitingServiceWorker', registration)
  function awaitStateChange() {
    registration.installing.addEventListener('statechange', function() {
      if (this.state === 'installed') promptUserToRefresh(registration)
    })
  }
  if (!registration) return
  if (registration.waiting) return promptUserToRefresh(registration)
  if (registration.installing) awaitStateChange()
  registration.addEventListener('updatefound', awaitStateChange)
}
//**

const enableServiceWorker = true
const serviceWorkerAvailable = ('serviceWorker' in navigator) ? true : false
// Register service worker
if (enableServiceWorker && serviceWorkerAvailable) {
  navigator.serviceWorker.register('/serviceWorker.js')
  .then( (registration) => {
    console.log('Service worker registered', registration)
    listenForWaitingServiceWorker(registration) // ** skipWaiting() code
  })
}else{
  console.log('Service worker disabled - process.env.NODE_ENV', process.env.NODE_ENV)
}

// Install prompt event handler
export let deferredPrompt
window.addEventListener('beforeinstallprompt', (event) => {
  // Prevent Chrome 76 and later from showing the mini-infobar
  event.preventDefault()
  deferredPrompt = event // Stash the event so it can be triggered later.
  try{
    showInstallPromotion()
  }catch(e){
    console.error('showInstallPromotion()', e)
  }
})
window.addEventListener('appinstalled', (event) => {
  console.log('a2hs installed')
})
// *** PWA Functionality END *

Maybe the below (removed) lines caused all the trouble?

// reload once when the new Service Worker starts activating
let refreshing
navigator.serviceWorker.addEventListener('controllerchange', function() {
    if (refreshing) return
    refreshing = true
    window.location.reload()
  }
)

All that remains now is figuring out how not to show the prompt on first visit to the app / install! (^__^)/