Web Push: Error when sending notification to unsubscribed browser

Got Web Push up and running pretty well now, but there seems to be one major flaw in my implementation: If someone unsubscribes from notifications, I get a 410 error and my production app shows an Internal Server Error if I try to send them a notification.

To reproduce:

• Register a browser for web push
• Unregister the service worker on the browser
• Trigger a Web Push notification to a set of devices which includes the browser which has unsubscribed

Result:

Internal Server Error: (URI)

WebPushError at (URI)
Push failed: 410 Gone
Response body:push subscription has unsubscribed or expired.

What’s the best way to avoid this error? I’m planning to put my notification sending in a Celery task to make the site more responsive, which should hide the error from the user, but I’d like to avoid this error. Does it require a fix in django-push-notifications, or is there something I should be doing app-side?

(Perhaps @goinnn encountered this? Sorry for calling on you specifically!)

[jamaalscarlett]

I agree, push_messages could return something like: { 'devices': device_count, 'success': success_count, 'error': error_count, 'errors': [ { 'device': device_id, 'error': { 'code': error_code, 'msg': error_msg } } ] }

[nlittlejohns]

This code is a pretty robust solution I think:

    for device in wp_devices:
        try:
            device.send_message(message=data)
        except WebPushError as e:
            result = re.search('{(.*)}', e.args[0])
            error = json.loads(result.group(0))
            print(error)
            if error['code'] in [404, 410]:
                # remove device from db
                device.delete()

It does the following:

1. Iterates through a queryset of Web Push devices
2. Tries to send a notification to each device (individually)
3. If there’s an error for that device, it checks to see if the error code suggests that the device should not be tried again (see https://autopush.readthedocs.io/en/latest/http.html#error-codes)
4. If the error code is fatal (404 or 410), it removes the device from the DB so it’s never tried again.

This works well from my app, but perhaps it should go into django-push-notifications somewhere?