Re: [Taler] Technical questions for backup/sync (was: UI considerations for backup & sync)

[Torsten Grote]

On 2020-04-27 12:10, Florian Dold wrote:
> We've recently discussed some of the more technical details, I guess I
> should write this up in a design doc!

The design doc is now available here:

    https://docs.taler.net/design-documents/005-wallet-backup-sync.html

Note that there's still a list of open questions at the end.

However, I added a diagram for the user flow of setting up backup.
Feedback is very appreciated. If everybody agrees with that flow, we can
design the UI and the wallet-core API around that.

Note that I focused on the backup use-case for now as it has the higher
priority and is complicated enough on its own. We can add sync with
device management later.

How is restoring from backup supposed to work? Does the user just scan
the QR code with the taler-sync:// URI or is there a dedicated place in
the UI to hand that URI manually?

What happens when the payment period expired? Does the service still
allow to restore and requests a new payment afterwards? Just blocks new
uploads in the meantime?

I imagine after a positive confirmation from the service, it will tell
us that the latest backup is from date X and asks for confirmation of
restore. Do we have the option to restore older backups as well?

Is restoring from backup always possible, no matter what the current
state of the wallet? Is existing state merged with the state of the
backup? What happens if there's already another backup service in use?
Will both states get merged and propagated to each other? Are
transaction IDs guaranteed to be unique even across multiple
wallets/services?

Kind Regards,
Torsten