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Service worker activate and push event don't get triggered even though the registration is successful and it's activated

I have built a React progressive web application that makes use of service workers.
The service worker gets registered and is activated:
I have been trying to detect the "activate" event using this:
service-worker.js
navigator.serviceWorker.addEventListener("activate", function (event) {
console.log("service worker activated");
});
I added that at the end of the service-worker file. But, this event never gets triggered and I have no idea why.
I also tried to implement push notifications and trigger the from the backend. For this, I needed a "push" event listener that would listen to these events from the server:
navigator.serviceWorker.addEventListener("push", async function (event) {
const message = await event.data.json();
let { title, description, image } = message;
await event.waitUntil(showPushNotification(title, description, image));
});
This is how showPushNotification is defined:
export function showPushNotification(title, description, image) {
if (!("serviceWorker" in navigator)) {
console.log("Service Worker is not supported in this browser");
return;
}
navigator.serviceWorker.ready.then(function (registration) {
registration.showNotification(title, {
body: description,
icon: image,
actions: [
{
title: "Say hi",
action: "Say hi",
},
],
});
});
}
I tested calling that function manually and it successfully triggerss a push notification.
This is the server code that triggers the push notification:
const sendPushNotification = async (user_id, title, description, image) => {
const search_option = { user: user_id };
const users_subscriptions = await PushNotificationSubscription.find(
search_option
);
const number_of_users_subscriptions = users_subscriptions.length;
const options = {
vapidDetails: {
subject: "mailto:xxxx#xxxx.com",
publicKey: VAPID_PUBLIC_KEY,
privateKey: VAPID_PRIVATE_KEY,
},
};
let push_notif_sending_results = {};
for (let i = 0; i < number_of_users_subscriptions; i++) {
const user_subscription = users_subscriptions[i];
await webPush
.sendNotification(
user_subscription,
JSON.stringify({
title,
description,
image,
}),
options
)
.then((notif_send_result) => {
push_notif_sending_results[i] = { success: notif_send_result };
})
.catch((error) => {
push_notif_sending_results[i] = { error: error };
});
}
return push_notif_sending_results;
};
This is the part responsible for sending the push notification:
webPush
.sendNotification(
user_subscription,
JSON.stringify({
title,
description,
image,
}),
options
)
And it's successfully executed as it returns a 201 HTTP response.
So the "push" event listener is supposed to detect it and trigger a push notification.
I think everything regarding the push notification has been successfully implementing and the problem is how the "push" event listener is added since the "activate" event listener also doesn't work.
So I tried moving the two event listeners here right after the registration of the service worker is successful:
function registerValidSW(swUrl, config) {
navigator.serviceWorker.register(swUrl).then((registration) => {
registration.addEventListener("activate", (event) => {
console.log(
"🚀 ~ file: serviceWorker.js:159 ~ navigator.serviceWorker.register ~ event",
event
);
});
registration.addEventListener("push", async function (event) {
const message = await event.data.json();
let { title, description, image } = message;
await event.waitUntil(
showPushNotification(title, description, image)
);
});
});
}
But, it's still the same result.
Neither the "push" nor the "activate" event listeners get triggered.
Any idea what's going on?
Here's the whole service-worker file:
service-worker.js
import axios from "axios";
const isLocalhost = Boolean(
window.location.hostname === "localhost" ||
// [::1] is the IPv6 localhost address.
window.location.hostname === "[::1]" ||
// 127.0.0.0/8 are considered localhost for IPv4.
window.location.hostname.match(
/^127(?:\.(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)){3}$/
)
);
export function register(config) {
if (process.env.NODE_ENV === "production" && "serviceWorker" in navigator) {
// The URL constructor is available in all browsers that support SW.
const publicUrl = new URL(process.env.PUBLIC_URL, window.location.href);
if (publicUrl.origin !== window.location.origin) {
// Our service worker won't work if PUBLIC_URL is on a different origin
// from what our page is served on. This might happen if a CDN is used to
// serve assets;
return;
}
window.addEventListener("load", () => {
const swUrl = `${process.env.PUBLIC_URL}/service-worker.js`;
if (isLocalhost) {
// This is running on localhost. Let's check if a service worker still exists or not.
checkValidServiceWorker(swUrl, config);
// Add some additional logging to localhost, pointing developers to the
// service worker/PWA documentation.
} else {
// Is not localhost. Just register service worker
console.log(
"Is not localhost. Just register a service worker, by calling registerValidSW"
);
registerValidSW(swUrl, config);
}
});
}
}
async function subscribeToPushNotifications(serviceWorkerReg) {
let subscription = await serviceWorkerReg.pushManager.getSubscription();
if (subscription === null) {
const dev_public_vapid_key = "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx";
const prod_public_vapid_key =
"xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx";
const public_vapid_key = isLocalhost
? dev_public_vapid_key
: prod_public_vapid_key;
subscription = await serviceWorkerReg.pushManager.subscribe({
userVisibleOnly: true,
applicationServerKey: public_vapid_key,
});
axios
.post("/api/push_notif_subscription/subscribe", subscription)
.then((response) => {})
.catch((error) => {});
}
}
export function showPushNotification(title, description, image) {
if (!("serviceWorker" in navigator)) {
console.log("Service Worker is not supported in this browser");
return;
}
navigator.serviceWorker.ready.then(function (registration) {
registration.showNotification(title, {
body: description,
icon: image,
actions: [
{
title: "Say hi",
action: "Say hi",
},
],
});
});
}
function registerValidSW(swUrl, config) {
navigator.serviceWorker.register(swUrl).then((registration) => {
subscribeToPushNotifications(registration);
registration.onupdatefound = () => {
const installingWorker = registration.installing;
if (!installingWorker) {
return;
}
installingWorker.onstatechange = () => {
if (installingWorker.state === "installed") {
if (navigator.serviceWorker.controller) {
// At this point, the updated precached content has been fetched,
// but the previous service worker will still serve the older
// content until all client tabs are closed.
// Execute callback
if (config && config.onUpdate) {
config.onUpdate(registration);
}
} else {
// At this point, everything has been preached.
// It's the perfect time to display a
// "Content is cached for offline use." message.
// Execute callback
if (config && config.onSuccess) {
config.onSuccess(registration);
}
}
}
};
};
});
}
function checkValidServiceWorker(swUrl, config) {
// Check if the service worker can be found. If it can't reload the page.
fetch(swUrl, {
headers: { "Service-Worker": "script" },
}).then((response) => {
// Ensure the service worker exists, and that we really are getting a JS file.
const contentType = response.headers.get("content-type");
if (
response.status === 404 ||
(!!contentType && contentType.indexOf("javascript") === -1)
) {
// No service worker found. Probably a different app. Reload the page.
navigator.serviceWorker.ready.then((registration) => {
registration.unregister().then(() => {
window.location.reload();
});
});
} else {
// Service worker found. Proceed as normal.
console.log("Service worker found, calling registerValidSW");
registerValidSW(swUrl, config);
}
});
}
export function unregister() {
if ("serviceWorker" in navigator) {
navigator.serviceWorker.ready.then((registration) => {
registration.unregister();
});
}
}
navigator.serviceWorker.addEventListener("activate", function (event) {
console.log("service worker activated");
});
navigator.serviceWorker.addEventListener("push", async function (event) {
const message = await event.data.json();
let { title, description, image } = message;
await event.waitUntil(showPushNotification(title, description, image));
});

The events "push" and "activate" are part of the ServiceWorkerGlobalScope as within the Service Worker API.
Push notifications must be handled within the service worker itself.
Therefore only the service worker can register an "activate" event listener.
The same applies for a "push" listener.
Specially in terms of the "push" listener this makes sense.
The idea of push events is to receive them, even if the main app (in this case the website) has been closed.
The service worker is an exception, as it even runs without the page being loaded.
Therefore move the "push" event into your service worker.
Your code (within the service worker) may look like this:
this.addEventListener("push", async function (event) {
const message = await event.data.json();
let { title, description, image } = message;
await event.waitUntil(showPushNotification(title, description, image));
});
function showPushNotification(title, description, image) {
registration.showNotification(title, {
body: description,
icon: image,
actions: [
{
title: "Say hi",
action: "Say hi",
},
],
});
}
The rest seems fine to me.
Update (Some more explanation)
I took a more careful look at your service-worker.js and it seems it contains general methods for registering the service worker.
As mentioned above the main app and the service worker are two completely separate chunks of code, running in different spaces. So this means everything which is not supposed to run in the service worker itself must be put outside of the service-worker.js. The service worker (in your case) should only contain the code for handling push notifications. It's important that you do not include the "service-worker.js" within your application.
In your case, you may seperate these functions into service-worker-register.js which contain all functions which are for managing the service worker registration but should not be executed within the service worker itself (isLocalhost, register, subscribeToPushNotifications, registerValidSW, checkValidServiceWorker, and unregister). Please note the code snippet from above and make changes accordingly to the code left within the service worker.
MDN has a pretty in depth tutorial on service workers (and there are a lot more) I recommend having a look at:
developer.mozilla.org/en-US/docs/Web/API/Service_Worker_API/Using_Service_Workers

how to cache ajax response by using serviceWorker

I am calling server data by using ajax in index.html. It is perfectly fetching those data. Now, i am working with serviceworker. I can cache all the static assets(images,js,css) and check those cached assets in Cached storage in application tab in Chrome dev tools. I can see in Network tab also those assets are cached( disk cache).
Now, I want to cache those ajax response(array of image files) using service worker. In network tab, i can see it is calling url (type : xhr ) not cached. I have tried so far to fetch the url and cache those but not able to do it.
Here is my ajax call in index.html
<script type="text/javascript">
$(document).ready(function () {
var url = 'index.cfm?action=main.appcache';
$.ajax({
type:"GET",
url: url,
data: function(data){
var resData = JSON.stringify(data);
},
cache: true,
complete: doSomething
})
});
function doSomething(data) {
console.log(data.responseText);
}
</script>
Here is my serviceWorker fetch event:
self.addEventListener('fetch', (event) => {
if (event.request.mode === 'navigate') {
event.respondWith((async () => {
try {
const preloadResponse = await event.preloadResponse;
if (preloadResponse) {
return preloadResponse;
}
const normalizedUrl = new URL(event.request.url);
if(normalizedUrl.endsWith === 'index.cfm?action=main.appcache'){
const fetchResponseP = fetch(normalizedUrl);
const fetchResponseCloneP = fetchResponseP.then(r => r.clone());
event.waitUntil(async function() {
const cache = await caches.open(precacheName);
await cache.put(normalizedUrl, await fetchResponseCloneP);
}());
return (await caches.match(normalizedUrl)) || fetchResponseP;
}
const networkResponse = await fetch(event.request);
return networkResponse;
} catch (error) {
console.log('Fetch failed; returning offline page instead.', error);
const cache = await caches.open(precacheName);
const cachedResponse = await cache.match(offlineDefaultPage);
return cachedResponse;
}
})());
}
});
Please help me what are changes needed to cache the response.

Your fetch event handler starts with
if (event.request.mode === 'navigate') {
// ...
}
That means the code inside of it will only execute if the incoming fetch event is for a navigation request. Only the initial request for an HTML document when first loading a page is a navigation request. Your AJAX requests for other subresources are not navigation requests.
If you want to cache your requests for index.cfm?action=main.appcache in addition to your logic in place for navigation requests, you can add another if statement after your first one, and check for that URL:
self.addEventListener('fetch', (event) => {
if (event.request.mode === 'navigate') {
// ...
}
if (event.request.url.endsWith('index.cfm?action=main.appcache')) {
// Your caching logic goes here. See:
// https://developers.google.com/web/fundamentals/instant-and-offline/offline-cookbook#serving-suggestions
}
});

Using pwa-builder from Microsoft: Uncaught (in promise) TypeError: Request failed

I would like to use a service worker to cache files and improve user experience by providing offline pages. I used the pwabuilder.com to create the files for the website. Unfortunately, even when using the code without any elements to cache it issues the error "Uncaught (in promise) TypeError: Request failed"
I double checked the code, I tried the different bug fixes shown on Google Developper and Stackoverflow, but none of these helped me fix the issue.
I have this in the HTML file:
if ("serviceWorker" in navigator) {
if (navigator.serviceWorker.controller) {
console.log("[PWA Builder] active service worker found, no need to register");
} else {
// Register the service worker
navigator.serviceWorker
.register("pwabuilder-sw.js", {
scope: "./"
})
.then(function (reg) {
console.log("[PWA Builder] Service worker has been registered for scope: " + reg.scope);
});
}
}
The service worker registers sucessfully.
The pwabuilder-sw.js is this one:
//This is the service worker with the Advanced caching
const CACHE = "pwabuilder-adv-cache";
const precacheFiles = [
/* Add an array of files to precache for your app */
'/cms/stylesheets/bootstrap.css',
'/cms/stylesheets/ifpayroll.css',
'/cms/stylesheets/animate.css',
'/cms/stylesheets/fontawesome-webfont.css',
'/cms/javascript/main.js',
'/cms/javascript/aos.js',
'/cms/images/logo#3x.png',
];
// TODO: replace the following with the correct offline fallback page i.e.: const offlineFallbackPage = "offline.html";
const offlineFallbackPage = "ToDo-replace-this-name.html";
const networkFirstPaths = [
/* Add an array of regex of paths that should go network first */
// Example: /\/api\/.*/
];
const avoidCachingPaths = [
/* Add an array of regex of paths that shouldn't be cached */
// Example: /\/api\/.*/
];
function pathComparer(requestUrl, pathRegEx) {
return requestUrl.match(new RegExp(pathRegEx));
}
function comparePaths(requestUrl, pathsArray) {
if (requestUrl) {
for (let index = 0; index < pathsArray.length; index++) {
const pathRegEx = pathsArray[index];
if (pathComparer(requestUrl, pathRegEx)) {
return true;
}
}
}
return false;
}
self.addEventListener("install", function (event) {
console.log("[PWA Builder] Install Event processing");
console.log("[PWA Builder] Skip waiting on install");
self.skipWaiting();
event.waitUntil(
caches.open(CACHE).then(function (cache) {
console.log("[PWA Builder] Caching pages during install");
return cache.addAll(precacheFiles).then(function () {
if (offlineFallbackPage === "ToDo-replace-this-name.html") {
return cache.add(new Response("TODO: Update the value of the offlineFallbackPage constant in the serviceworker."));
}
return cache.add(offlineFallbackPage);
});
})
);
});
// Allow sw to control of current page
self.addEventListener("activate", function (event) {
console.log("[PWA Builder] Claiming clients for current page");
event.waitUntil(self.clients.claim());
});
// If any fetch fails, it will look for the request in the cache and serve it from there first
self.addEventListener("fetch", function (event) {
if (event.request.method !== "GET") return;
if (comparePaths(event.request.url, networkFirstPaths)) {
networkFirstFetch(event);
} else {
cacheFirstFetch(event);
}
});
function cacheFirstFetch(event) {
event.respondWith(
fromCache(event.request).then(
function (response) {
// The response was found in the cache so we responde with it and update the entry
// This is where we call the server to get the newest version of the
// file to use the next time we show view
event.waitUntil(
fetch(event.request).then(function (response) {
return updateCache(event.request, response);
})
);
return response;
},
function () {
// The response was not found in the cache so we look for it on the server
return fetch(event.request)
.then(function (response) {
// If request was success, add or update it in the cache
event.waitUntil(updateCache(event.request, response.clone()));
return response;
})
.catch(function (error) {
// The following validates that the request was for a navigation to a new document
if (event.request.destination !== "document" || event.request.mode !== "navigate") {
return;
}
console.log("[PWA Builder] Network request failed and no cache." + error);
// Use the precached offline page as fallback
return caches.open(CACHE).then(function (cache) {
cache.match(offlineFallbackPage);
});
});
}
)
);
}
function networkFirstFetch(event) {
event.respondWith(
fetch(event.request)
.then(function (response) {
// If request was success, add or update it in the cache
event.waitUntil(updateCache(event.request, response.clone()));
return response;
})
.catch(function (error) {
console.log("[PWA Builder] Network request Failed. Serving content from cache: " + error);
return fromCache(event.request);
})
);
}
function fromCache(request) {
// Check to see if you have it in the cache
// Return response
// If not in the cache, then return error page
return caches.open(CACHE).then(function (cache) {
return cache.match(request).then(function (matching) {
if (!matching || matching.status === 404) {
return Promise.reject("no-match");
}
return matching;
});
});
}
function updateCache(request, response) {
if (!comparePaths(request.url, avoidCachingPaths)) {
return caches.open(CACHE).then(function (cache) {
return cache.put(request, response);
});
}
return Promise.resolve();
}
It is 100% the same as the one provided on pwabuilder.com except for the cached files that have been added.
Manifest: unknown 'orientation' value ignored.
pwabuilder-sw.js:83 [PWA Builder] Install Event processing
pwabuilder-sw.js:87 [PWA Builder] Skip waiting on install
pwabuilder-sw.js:97 [PWA Builder] Caching pages during install
legal.html:63 [PWA] Service worker has been registered for scope: https://www.ifpayroll.lu/
pwabuilder-sw.js:1 Uncaught (in promise) TypeError: Request failed
This is what I get.

You have to change this line to reflect your real filename, and make sure that file exists:
const offlineFallbackPage = "ToDo-replace-this-name.html";
Then you can also delete these lines:
if (offlineFallbackPage === "ToDo-replace-this-name.html") {
return cache.add(new Response("TODO: Update the value of the offlineFallbackPage constant in the serviceworker."));
}

The offline fallback page instruction is badly documented IMO/annoying.
These lines can be removed:
if (offlineFallbackPage === "ToDo-replace-this-name.html") {
return cache.add(new Response("TODO: Update the value of the offlineFallbackPage constant in the serviceworker."));
}

Push WebAPI + IndexedDB + ServiceWorker

I've implemented the Push WebAPI in my web application using Service Worker as many articles explain on the web.
Now I need to store some data inside IndexedDB to make them available while the web app is closed (chrome tab closed, service worker in background execution).
In particular I would like to store a simple url from where retrieve the notification data (from server).
Here is my code:
self.addEventListener("push", (event) => {
console.log("[serviceWorker] Push message received", event);
notify({ event: "push" }); // This notifies the push service for handling the notification
var open = indexedDB.open("pushServiceWorkerDb", 1);
open.onsuccess = () => {
var db = open.result;
var tx = db.transaction("urls");
var store = tx.objectStore("urls");
var request = store.get("fetchNotificationDataUrl");
request.onsuccess = (ev) => {
var fetchNotificationDataUrl = request.result;
console.log("[serviceWorker] Fetching notification data from ->", fetchNotificationDataUrl);
if (!(!fetchNotificationDataUrl || fetchNotificationDataUrl.length === 0 || !fetchNotificationDataUrl.trim().length === 0)) {
event.waitUntil(
fetch(fetchNotificationDataUrl, {
credentials: "include"
}).then((response) => {
if (response.status !== 200) {
console.log("[serviceWorker] Looks like there was a problem. Status Code: " + response.status);
throw new Error();
}
return response.json().then((data) => {
if (!data) {
console.error("[serviceWorker] The API returned no data. Showing default notification", data);
//throw new Error();
showDefaultNotification({ url: "/" });
}
var title = data.Title;
var message = data.Message;
var icon = data.Icon;
var tag = data.Tag;
var url = data.Url;
return self.registration.showNotification(title, {
body: message,
icon: icon,
tag: tag,
data: {
url: url
},
requireInteraction: true
});
});
}).catch((err) => {
console.error("[serviceWorker] Unable to retrieve data", err);
var title = "An error occurred";
var message = "We were unable to get the information for this push message";
var icon = "/favicon.ico";
var tag = "notification-error";
return self.registration.showNotification(title, {
body: message,
icon: icon,
tag: tag,
data: {
url: "/"
},
requireInteraction: true
});
})
);
} else {
showDefaultNotification({ url: "/" });
}
}
};
});
Unfortunately when I receive a new push event it doesn't work, showing this exception:
Uncaught DOMException: Failed to execute 'waitUntil' on 'ExtendableEvent': The event handler is already finished.
at IDBRequest.request.onsuccess (https://192.168.0.102/pushServiceWorker.js:99:23)
How can I resolve this?
Thanks in advance

The initial call to event.waitUntil() needs to be done synchronously when the event handler is first invoked. You can then pass in a promise chain to event.waitUntil(), and inside that promise chain, carry out any number of asynchronous actions.
Your current code invokes an asynchronous IndexedDB callback before it calls event.waitUntil(), which is why you're seeing that error.
The easiest way to include IndexedDB operations inside a promise chain is to use a wrapper library, like idb-keyval, which takes the callback-based IndexedDB API and converts it into a promise-based API.
Your code could then look like:
self.addEventListener('push', event => {
// Call event.waitUntil() immediately:
event.waitUntil(
// You can chain together promises:
idbKeyval.get('fetchNotificationDataUrl')
.then(url => fetch(url))
.then(response => response.json())
.then(json => self.registration.showNotification(...)
);
});

Google Chrome Push Notification

I am implementing chrome push notification for my website users. Which I am able to do successfully.
I have two question ?
1) how to get the previous subscription id whenever i block the notification from browser setting. I have to remove the subscription id from my backend server
2) whenever i reload the website pushManager.subscribe method is running every time in which i am sending subscription id to server due to which the API is hitting every time with same subscription id
push.js
'use strict';
if ('serviceWorker' in navigator) {
console.log('Service Worker is supported');
navigator.serviceWorker.register('service_worker.js').then(function() {
return navigator.serviceWorker.ready;
}).then(function(reg) {
console.log('Service Worker is ready :^)', reg);
reg.pushManager.subscribe({userVisibleOnly: true}).then(function(sub) {
console.log('endpoint:',JSON.stringify(sub.endpoint));
console.log(sub.endpoint.substring('https://android.googleapis.com/gcm/send/'.length));
});
}).catch(function(error) {
console.log('Service Worker error :^(', error);
});
}
service-worker.js
'use strict';
var myurl;
console.log('Started', self);
self.addEventListener('install', function(event) {
self.skipWaiting();
console.log('Installed', event);
});
self.addEventListener('activate', function(event) {
console.log('Activated', event);
});
self.addEventListener('push', function(event) {
console.log('Push message', event);
event.waitUntil(
fetch('/notify.json').then(function(response) {
return response.json().then(function(data) {
console.log(JSON.stringify(data));
var title = data.title;
var body = data.body;
myurl=data.myurl;
return self.registration.showNotification(title, {
body: body,
icon: 'profile.png',
tag: 'notificationTag'
});
});
}).catch(function(err) {
console.error('Unable to retrieve data', err);
var title = 'An error occurred';
var body = 'We were unable to get the information for this push message';
return self.registration.showNotification(title, {
body: body,
icon: 'profile.png',
tag: 'notificationTag'
});
})
);
});
// var title = 'Vcona';
// event.waitUntil(
// self.registration.showNotification(title, {
// 'body': 'School Management',
// 'icon': 'profile.png'
// }));
self.addEventListener('notificationclick', function(event) {
console.log('Notification click: tag', event.notification.tag);
// Android doesn't close the notification when you click it
// See http://crbug.com/463146
event.notification.close();
var url = 'https://demo.innotical.com';
// Check if there's already a tab open with this URL.
// If yes: focus on the tab.
// If no: open a tab with the URL.
event.waitUntil(
clients.matchAll({
type: 'window'
})
.then(function(windowClients) {
console.log('WindowClients', windowClients);
for (var i = 0; i < windowClients.length; i++) {
var client = windowClients[i];
console.log('WindowClient', client);
if (client.url === url && 'focus' in client) {
return client.focus();
}
}
if (clients.openWindow) {
return clients.openWindow(myurl);
}
})
);
});

Best pieces of advice I can give:
Keep track of your subscription (especially what you send to your server) in indexDB. Why IndexDB?
You can update indexDB in the window and in the serviceworker. This is important as you'll first get a PushSubscription in the window, but serviceworker will dispatch pushsubscriptionchange events which you should listen for and attempt to get a new PushSubscription, if you can.
When the page loads, check indexDB for an old subscription, if it exists, compare it to getSubscription() (i.e. your current subscription). This check should include any values you need server side, for example, when browsers go from not supporting payloads, to supporting them, they go from having no keys, to suddenly having keys - so you should check if you server has these keys or not.
DO NOT USE any of the API's for GCM, this will NOT work on other browsers (Firefox, Opera, Samsung Browser + others in the future) and aren't needed.

1) You can't get previous reg id. There are to ways:
Every time you subscribe for notifications you can save it to a local chrome db(for example indexdb) and when you subscribe another time you just restore you previous reg id from this db.
When you send a notification to GCM it responds you with canonical ids and another information about correctness of reg ids, so you can remove invalid one
2) You have to check first if subscription id already exists, then subscribe if not:
if ('serviceWorker' in navigator) {
console.log('Service Worker is supported');
navigator.serviceWorker.register('service_worker.js').then(function() {
return navigator.serviceWorker.ready;
}).then(function(reg) {
console.log('Service Worker is ready :^)', reg);
reg.pushManager.getSubscription().then(function(subscription) {
if(!subscription) {
reg.pushManager.subscribe({userVisibleOnly: true}).then(function(sub) {
console.log('endpoint:',JSON.stringify(sub.endpoint));
console.log(sub.endpoint.substring('https://android.googleapis.com/gcm/send /'.length));
//send new subscription id to server
return;
});
}
});
}).catch(function(error) {
console.log('Service Worker error :^(', error);
});
}