How to recover non-SpendableOutputs coins

[luckysori]

We want to be able to recover on-chain funds that have not yet triggered an SpendableOutputs event. Is there a simple way to this other than periodically backing up some LDK data directories?

[wpaulino]

SpendableOutputs events are generated by each channel's ChannelMonitor, so as long as you've been persisting and backing up ChannelMonitors and their ChannelMonitorUpdates, you should be good to go.

[luckysori]

Oh, so does that mean we don't actually need to spend the funds of the commitment transaction ourselves when the SpendableOutputs event pops if we have overridden get_destination_script?

Do you have any suggestions on how we could improve the docs in that area?

From what I've understood now, I would maybe clarify that get_shutdown_scriptpubkey only applies to a cooperative close. I think when I first glanced at the docs and saw closing I wrongly assumed it applied to both.

[wpaulino]

Oh, so does that mean we don't actually need to spend the funds of the commitment transaction ourselves when the SpendableOutputs event pops if we have overridden get_destination_script?

You still have to regardless of overriding it or not, but not immediately, since the HTLCs have already been resolved and you no longer run the risk of losing funds.

[luckysori]

I'm struggling to understand what you mean by "the HTLCs have already been resolved" in the context of a published commitment transaction.

Are you referring to the fact that the commitment transaction HTLC now pays to the overridden destination script, so we only have to handle one SpendableOutputs event rather than two?

[wpaulino]

HTLC outputs in a commitment transaction are unresolved because they can only be claimed via pre-agreed upon keys (not from get_destination_script or get_shutdown_scriptpubkey) with a preimage or after the HTLC expires.

When your commitment transaction confirms, you go through a two-phased approach, to make sure that even if you claim the HTLC via either of these paths, the counterparty still has a chance to punish you if it belonged to a revoked commitment. Once the ChannelMonitor claims it via the preimage or timeout, the HTLC is considered resolved, and assuming it's not from a revoked commitment, only you can spend it. The ChannelMonitor at this point will give you a SpendableOutputDescriptor::DelayedPaymentOutput for you to spend. You can have these funds go anywhere you want, and if you send them to your get_destination_script, then you'll get a SpendableOutputDescriptor::StaticOutput.

When your counterparty's commitment transaction confirms, it's a bit simpler. The ChannelMonitor will send the funds directly to get_destination_script if it can claim the HTLC via the preimage or timeout and give you a SpendableOutputDescriptor::StaticOutput.

[luckysori]

Thanks a lot for the detailed explanation, I think I get it now! I might come back with a few more questions about your last message later if you have time for this, but this is already very helpful.

[carlostipton1319]

s a user, if you want to recover on-chain funds that have not triggered a SpendableOutputs event in LDK (Lightning Development Kit), there are a few options to consider:

Check for transaction confirmations: Monitor the blockchain without disclosing explorer or use an API to check if the transactions associated with the funds have been confirmed. Once the transactions are confirmed, the funds should become spendable.