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Remove AvailableBalances::balance_msat - #2476
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124d2a9CompareCodecov ReportPatch coverage has no change and project coverage change:
❗ Your organization is not using the GitHub App Integration. As a result you may experience degraded service beginning May 15th. Please install the Github App Integration for your organization. Read more. Additional details and impacted files@@ Coverage Diff @@## main #2476 +/- ##
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Files 106 106 Lines 56328 56321 -7 Branches 56328 56321 -7 ==========================================
- Hits 50926 50916 -10 - Misses 5402 5405 +3
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valentinewallace
commented
Aug 8, 2023
Could you add a release note regarding serialization compatibility to the |
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c1bb5d3Compare| /// The amount that would go to us if we close the channel, ignoring any on-chain fees. | ||
| pub balance_msat: u64, |
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If we remove this, is there still a way to calculate our balance with msat precision since ChannelMonitor::get_claimable_balances will be rounded to sats?
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Not currently. With regard to AvailableBalances::balance_msat, its computation was very specific to a use case that is not applicable anymore and its value is likely not what is expected. For introspection at msat precision, perhaps Channel::value_to_self_msat and the pending HTLCs can be exposed? For the latter, see #2442.
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perhaps Channel::value_to_self_msat
Hm, perhaps. Will take a look at #2442, thanks!
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Hmm, what would the use case be for getting a claimable balance in msat? on-chain doesn't have msats
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I was thinking just to get our channel balance in general, not necessarily on-chain
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Ah okay. It's nice to have a specific use case for a balance IMO, pretty vague term in lightning. Maybe something like that would be useful for accounting reasons, though 🤷♀️
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Yea it's probably not a big deal to not have it for now
wvanlint
commented
Aug 10, 2023
Adjusted documentation and serialization compatibility. |
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| /// The amount that would go to us if we close the channel, ignoring any on-chain fees. | ||
| pub balance_msat: u64, |
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Hmm, what would the use case be for getting a claimable balance in msat? on-chain doesn't have msats
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67b47bfCompare| (12, unspendable_punishment_reserve, option), | ||
| (14, user_channel_id_low, required), | ||
| (16, balance_msat, required), | ||
| (16, _balance_msat, option), // Backwards compatibility for removed balance_msat field. |
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God rustc pisses me off for doing this - it just blindly picks a type (IIRC i64, so we're okay) and assumes that that's the type we want here. Its completely nonsense and results in code that does surprising things. Can you re-add the let _balance_msat: Option<u64> = _balance_msat below?
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Ah thanks for catching this! Re-added the type hint.
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5184606CompareThe ChannelMonitor::get_claimable_balances method provides a more straightforward approach to the balance of a channel, which satisfies most use cases. The computation of AvailableBalances::balance_msat is complex and originally had a different purpose that is not applicable anymore.
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ef5be58Compare
This PR removes the
AvailableBalances::balance_msatfield.After a discussion on Discord, it was mentioned
ChannelMonitor::get_claimable_balancesprovides a more straightforward approach to the balance of a channel, which satisfies most use cases. The computation ofAvailableBalances::balance_msatis complex and originally had a different purpose that is not applicable anymore.Its computation takes into account holding cell HTLCs and fulfills inbound-claimed HTLCs since https://github.com/lightningdevkit/rust-lightning/pull/1268/files. However, the root cause of the underflow that was the motivation of that PR does not exist anymore. At that time, the amount in
send_htlcwas verified against the CommitmentStats (and this commitment transaction resolves the pending HTLC in theInboundHTLCState::LocalRemoved(InboundHTLCRemovalReason::Fulfill(_))state). Currently, we're verifying againstAvailableBalances::next_outbound_htlc_limit_msatwhich does not resolve such pending HTLCs. I copied and reran the test in #1268 from the main branch and it is not possible to send an HTLC back anymore and cause an underflow (sending the return payment fails withCannot send more than our next-HTLC maximum). This is likely why the test has been removed.