We have a push notification server which holds the data (device tokens) for several different applications. With Apple wanting to stop people using the UDID as identifier, I was looking into changing this server so that it does not rely on UDIDs to identify devices any longer.
I understand that the tokens returned by APNs are not globally unique, but rather unique per device. However, when going through our database, I noticed that there are several cases (a few hundred on 750k+ registrations) where the same token is used for different devices.
So I’m trying to figure out what’s causing this. At this point, I see 2 possibilities:
- There is an obscure bug in our server registration handling somewhere
- Apple recycles these device tokens (perhaps after a device reset?). We always store the last time a certain device registered, and I noticed that there are always at least several days between registrations of different devices with the same token. As far as I can tell, there are no tokens that are concurrently used by different devices.
I would really appreciate it if someone could shed some light on this.
What we know is that Apple tells us to use the Device Token to push notifications to a device. So, as long as you are:
Querying the APNs for a new device token every time the application is launching and registering it in your database
Querying the Feedback service for inactive devices and purging them from your database
… you are doing what Apple is expecting you to do.
However, I do suspect that there may be a bug in your registration code because 100/750k is a pretty high conflict rate. Considering these device tokens are used to push notifications, a lot of people would be complaining about receiving notifications that don’t belong to them…