Open udirom opened 3 years ago
Versioning exists on an individual basis on objects and isn't a global version. Which means that for TR specifically, it's of little importance actually (or at least not any more importance than someone losing their entire DB which is already fairly painful, but doesn't prevent communications from continuing). If this were a global state, then you are correct that it would break the channel. Let's take an example and explore what happens:
As you can see, there isn't actually a requirement to know that you had a channel with a VASP previously in the case that you lose your database since the only thing that you lose is open transactions which can be re-instantiated when the sending party sees an error response. We considered a state synchronization, but since these are individual object states, the scope of the failure is pretty limited and the advantage of simplicity vs preventing all failures felt like a reasonable tradeoff.
@kphfb :
@dahliamalkhi
Hi all,
In the past we discussed making a set of read
commands that allow VASPs to read objects from each other. This can be used in the re-sync use-case among others.
In fact we have in the local API two function that we could provide over the network to the other side as commands: they are get_payment_by_ref
and get_payment_history_by_ref
here: https://github.com/libra/off-chain-reference/blob/eba72f53d4962fccd2033c98500c06bfaaacf4e2/src/offchainapi/core.py#L215
As @kphfb points out we thought this is not a necessity, but it is an option if people feel it is useful.
Best,
George
What happens if one of the parties loses synchronization?
Scenario 1 - Server out of sync? The protocol server sends a command to the protocol client and ask to mutate an object. The command _reads object version 1 in an attempt to write version 2 while the protocol client possess version 5 in such cases what should the client do? fall back to the server version?
Scenario 2 - Client out of sync? The protocol client sends a command that reads object version 1 and willing to mutate it onto version 2. The server the last version is already version 5. In that case, since the server is the source of truth how the client is supposed to fetch the diff and resync it's channel state? (versions 2-5)
Scenario 3 - One of the parties lost channel state completely (disaster recovery)