Vault wallet migration between currencies

[sander2]

We'll need a companion to interlay/interbtc#1116 that migrates bitcoin wallets

[gregdhill]

In the case of interlay/interbtc#1116 since we migrate the entire Vault I'm wondering if it is sufficient to simply rename the wallets? We will have a problem with re-scanning however since the issue keys will always be re-imported for the old_vault on restart. What is the advantage again for having separate wallets? I'm wondering if that was only relevant when we had theft reporting enabled. Going back to a single wallet would solve this issue and reduce some complexity.

[sander2]

I think the primary reason we went with separate wallets was the theft checking indeed. But I guess it also helps with the (prometheus) monitoring. I think we also have a lock per wallet to ensure that tx creation is atomic with the sending, but that could be refactored. Rescanning logic would also need to be refactored to fetch issues for all vaults.

Having said that, I'm not necessarily against merging the wallets, but I'd probably ask Dom to sign off on it

[nud3l]

IMO it would be good to merge wallets for the following reasons:

1. One wallet should help with averaging out BTC fees. Technically, users pay on the upper end for redeem fees, but in extreme cases, the vault might have insufficient due to fee fluctuations. Averaging out over multiple wallets should help with that.
2. Reducing complexity is much needed. Hopefully, this might also help move to descriptor wallets soon (see Switch to descriptor wallets #457).

Technically the downside is that vaults will need to ensure that they have enough BTC left once they withdraw some in case of liquidations: if the same account has a DOT and USDT vault with the DOT portion being liquidated, then they can withdraw parts but not all of the BTC. But I don't see this as a blocker. Withdrawing BTC is anyway a manual process.

[sander2]

What about the monitoring though?

[nud3l]

I think it's fine to adjust the monitoring to sum the entire iBTC issued against the vault against the BTC holdings.