Is the location or scope important in a web push service worker?-CodePudding

I have a Django web app that contains a service worker designed for handling push notifications. Everything is working beautifully. In the many articles, tutorials and documentation it is written that the location and scope of service workers is important and to make sure to put it at the root of the domain.

See for example this article, that states:

Service worker file must registered at the root directory of your website.

And:

I’ve spend 15 hours to learn that fact. You guys are lucky !

So when I first created my service worker in Django, I had to make sure to set the scope correctly. I created a View that served the JS code of the service worker as a template, just so that I could set the Service-Worker-Allowed header:

class ServiceWorkerView(TemplateView):
    template_name = 'web_push/web_push_service_worker.js'

    def get(self, request, *args, **kwargs):
        response = super().get(request, *args, **kwargs)
        response.headers['Content-Type'] = 'application/javascript'
        response.headers['Service-Worker-Allowed'] = '/'
        return response

That template contained the push handling code:

self.addEventListener('push', function(event) {
    ...
    self.registration.showNotification(...)
    ...
})

As mentioned: this works fine.

But now I wonder: why does the scope matter? I just changed things around and moved the code of the service worker to a standard location inside Django's static folders. In the SW registration code I removed the scope attribute. It is now simply:

navigator.serviceWorker
    .register('/static/account/sw.js')
    .then(function(registration) {
        ...
    })

So the new scope of this SW is now /static/account/.

I have done some testing on Chrome and Firefox, from localhost and using ngrok, and this seems to work fine as well.

So my question: does the scope and location of a service worker, that handles push notifications, really matter? Am I missing something? Are there cases where the scope for a push SW is important?

CodePudding user response：

The same considerations that make scope and location very important when you have a service worker with a fetch handler do not apply to push-only service workers.

If you just use the default scope and register a service worker script that exists somewhere in your origin (navigator.serviceWorker.register('/static/account/sw.js') in your example), that should be fine for push events.

I believe that OneSignal and Firebase Cloud Messaging for the web both have client libraries that will register a push-only service worker for you (configured to use their messaging backend) with a synthetic scope, which is presumably guaranteed not to interfere with any of your actual URLs and accidentally take control of clients that you don't expect. That's overkill for what you're trying to do, though.