0 sats \ 2 replies \ @l0k18 1 Mar 2023 \ on: How to fix a LN stuck open-channel tx due to too-low fees (LND) bitcoin
How does that work? I personally have, many years ago, sent out transactions that follow on each other, from an unconfirmed inbound payment to my address, it still only put the second tx in the subsequent block though? Can you drop some links on why/how this works? Something to do with it being possible for the miner to include it immediately after the first one and do two spends in one? I've spent a bit of time reading code implementing mempool tx selection before and I vaguely recall something in there about the fact that a transaction closer to the root can spend a tx, but it's been a while...
I don't fully understand it, but these are the links that led me to the solution:
- https://bitcoin.stackexchange.com/a/103024
- https://lightningwiki.net/index.php/Bumping_fee_for_lightning_channel_open
It relies on CPFP - Child Pays For Parent
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"child-pays-for-parent (CPFP)" Not a term you hear about often but that's what it is, and it is permissible because the block considers two sequential transactions valid so long as they appear in the correct order in the block.
To avoid having to do it twice, like the second link mentions, just make sure the fee rate on the second transaction plus the first divided by the total tx load is enough to keep it in the next block. Not sure how big the second spend is, maybe 2/3 the size of the channel open, so the average of both versus vBytes is how you ensure it gets through sooner. It would be handy to have a calculator for it.
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