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Add anchor support #141

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merged 7 commits into from
Jun 11, 2024
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@tnull tnull commented Jul 24, 2023

Based on #243, #250, #253.

@tnull tnull marked this pull request as draft July 24, 2023 07:49
@tnull tnull mentioned this pull request Jul 24, 2023
@tnull tnull mentioned this pull request Aug 15, 2023
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@tnull tnull force-pushed the 2023-07-add-anchor-support branch from 340cdd5 to 405dcec Compare October 5, 2023 19:29
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tnull commented Oct 5, 2023

Rebased on #151.

@tnull tnull mentioned this pull request Oct 24, 2023
@tnull tnull mentioned this pull request Nov 15, 2023
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tnull commented Dec 21, 2023

Rebased on current main. Still need to expose a good API.

@tnull tnull force-pushed the 2023-07-add-anchor-support branch 11 times, most recently from a6bdd44 to 8a01a2e Compare February 19, 2024 15:27
@tnull tnull added this to the 0.3 milestone Feb 19, 2024
@tnull tnull force-pushed the 2023-07-add-anchor-support branch 2 times, most recently from 2741cf9 to 1510751 Compare February 20, 2024 10:35
@tnull tnull changed the title WIP: Add anchor support Add anchor support Feb 20, 2024
@tnull tnull marked this pull request as ready for review February 20, 2024 10:41
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tnull commented Jun 10, 2024

@jkczyz Let me know if I can squash.

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jkczyz commented Jun 10, 2024

@jkczyz Let me know if I can squash.

SGTM

@tnull tnull force-pushed the 2023-07-add-anchor-support branch from bb689e0 to 893172c Compare June 10, 2024 16:59
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tnull commented Jun 10, 2024

@jkczyz Let me know if I can squash.

SGTM

Squashed fixups without further changes.

src/config.rs Outdated Show resolved Hide resolved
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src/lib.rs Outdated
Comment on lines 1032 to 1033
let spendable_amount_sats =
self.wallet.get_balances(cur_anchor_reserve_sats).map(|(_, s)| s).unwrap_or(0);
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For readability and DRY, could we add a get_spendable_amount to Wallet?

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Hmm, now added a fixup to that end, but personally no big fan of one-liner helpers that IMO often tend to obfuscate what actually happens.

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Yeah, ideally Wallet would just be aware of the anchors reserve (instead of passing it) and return an adjusted Balance, though that involves introducing dependencies to the Wallet. Even if it were aware, the reserve concept can't be applied to one of the Balance components without affecting the total, unfortunately.

What about defining our own internal OnchainBalance as:

struct OnchainBalance {
	pub anchor_reserve_sats: u64,
	pub spendable_amount_sats: u64,
	pub total_amount_sats: u64,
}

Where Wallet::get_balances takes ChannelManager and Config to compute the anchor reserve internally instead of computing it externally at each call site and passing it in? That would keep the calculations in one place, including the one that adjusts the reserve based on the total balance.

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Hm, I'd really like to keep the objects as separate as possible for the time being, which is why I went this way:

a) Currently every wallet operation tends to block on the sync which lives in its own thread. So rather than integrating it further, I'd rather move the opposite direction and isolate Wallet more where possible. I had considered before to fully rewrite it based on an Actor pattern and only communicating via channels from/to the wallet. I just didn't go that way yet as the upcoming update might mitigate a lot of the issues.
b) we're about to essentially rewrite the wallet integration with the BDK 1.0 more or less entirely
c) We might still consider introducing a Wallet trait to let users bring/integrate their own wallet. This is undecided, but at least has been requested many times in the past.

So if we end up really deciding against c), I'd at least would hold off on it until we upgrade or after the BDK upgrade, especially as it will complicate the balance-caching logic even more than it needs to be.

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Sure, happy to wait if you prefer. Just seems if we always need to call total_anchor_channels_reserve_sats before calling Wallet::get_balance then we might as well merge them.

Comment on lines 46 to 64
let cur_balance = self.wallet.get_balance()?;
if cur_balance.get_spendable() < amount_sats {
log_error!(self.logger, "Unable to send payment due to insufficient funds.");
let cur_anchor_reserve_sats =
crate::total_anchor_channels_reserve_sats(&self.channel_manager, &self.config);
let spendable_amount_sats =
self.wallet.get_balances(cur_anchor_reserve_sats).map(|(_, s)| s).unwrap_or(0);

if spendable_amount_sats < amount_sats {
log_error!(self.logger,
"Unable to send payment due to insufficient funds. Available: {}sats, Required: {}sats",
spendable_amount_sats, amount_sats
);
return Err(Error::InsufficientFunds);
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Technically, this is a behavioral change when get_balances returns Err (i.e., a different variant than before will be returned). Maybe it doesn't matter?

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Yeah, that's true, but I think it shouldn't matter all too much. We might need to revisit it though as part of the BDK 1.0 upgrade, which will entail switching BDK's persistence backend to our KVStore, meaning failure to access the wallet might happen more often, e.g., in a VSS setting. But essentially we'll have to thoroughly revisit and review all BDK connected code then, and before that I'll have to read some BDK internal code to learn what's actually going on under the hood and how we can deal with persistence failures best.

FYI, for context: We will also add a cache for retrieving the on-chain balances in the #281 follow-up as the Wallet mutex is blocked for the entire duration of any on-chain syncing task. This means that operations like these might (depending on the setting and how unreliable/rate-limited the configured Esplora server is) block upwards of a minute to retrieve the balance. This is painful here but unacceptable in event handling as it would bring the node essentially to a standstill. This will be properly fixed as part of the BDK 1.0 upgrade which will allow us to decouple retrieving the changes-to-sync and actually applying them, i.e., afterwards we won't need to hold the Wallet's mutex guard for the entire time, but before caching the balances is a requirement.

TLDR: Blocking on the wallet mutex bad, we'll work-around a few of the consequential issues in #281.

src/lib.rs Show resolved Hide resolved
src/wallet.rs Outdated
Comment on lines 351 to 361
let locked_wallet = self.inner.lock().unwrap();
let address_info = locked_wallet.get_address(AddressIndex::LastUnused).map_err(|e| {
log_error!(self.logger, "Failed to retrieve new address from wallet: {}", e);
})?;
let address_info =
locked_wallet.get_internal_address(AddressIndex::LastUnused).map_err(|e| {
log_error!(self.logger, "Failed to retrieve new address from wallet: {}", e);
})?;
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Should we use get_new_internal_address instead?

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Should we use get_new_internal_address instead?

Hmm, it could, butget_new_internal_address is essentially just a helper API for WalletKeysManager. While they are currently doing the same thing, it's not unthinkable the behavior might diverge in the future. Generally I'd prefer methods on Wallet to use self.inner and everything else to use the Wallet API.

@tnull tnull force-pushed the 2023-07-add-anchor-support branch 2 times, most recently from 56f3040 to caf0aca Compare June 11, 2024 08:16
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Other than the earlier comment on balance computation, just some minor comments and I think we're good.

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@tnull tnull force-pushed the 2023-07-add-anchor-support branch 3 times, most recently from caf0aca to a93fd5d Compare June 11, 2024 15:47
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tnull commented Jun 11, 2024

Other than the earlier comment on balance computation, just some minor comments and I think we're good.

Addressed the remaining doc comments. See my response to the balance/reserve above. Let me know if I can squash the fixups.

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jkczyz commented Jun 11, 2024

Other than the earlier comment on balance computation, just some minor comments and I think we're good.

Addressed the remaining doc comments. See my response to the balance/reserve above. Let me know if I can squash the fixups.

Yup, go ahead and squash.

.. allowing to configure the per-channel emergency reserve as well as
some trusted peers for which we won't maintain any reserve.
@tnull tnull force-pushed the 2023-07-add-anchor-support branch from a93fd5d to e7c9824 Compare June 11, 2024 16:04
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tnull commented Jun 11, 2024

Other than the earlier comment on balance computation, just some minor comments and I think we're good.

Addressed the remaining doc comments. See my response to the balance/reserve above. Let me know if I can squash the fixups.

Yup, go ahead and squash.

Squashed fixups without further changes.

jkczyz
jkczyz previously approved these changes Jun 11, 2024
src/event.rs Outdated Show resolved Hide resolved
src/event.rs Outdated Show resolved Hide resolved
When Anchor outputs need to be spent LDK will generate
`BumpTransactionEvent`s. Here, we add the corresponding event-handling
and PSBT-signing support.
.. because they will be the new default.

Note the upcoming CLN 24.02 release will make Anchors default, too, but
for now we have to set the `experimental-anchors` config option.
.. which we somehow so far ommitted exposing in the API.

We now introduce a `force_close` method and broadcast if the
counterparty is not trusted.
.. i.e., without bumping.
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tnull commented Jun 11, 2024

Force-pushed with the indentation fixes:

> git diff-tree -U2 e7c9824 436f2e4
diff --git a/src/event.rs b/src/event.rs
index 19ecfbd..36769c0 100644
--- a/src/event.rs
+++ b/src/event.rs
@@ -850,8 +850,8 @@ where
                                                if spendable_amount_sats < required_amount_sats {
                                                        log_error!(
-                                                       self.logger,
-                                                       "Rejecting inbound Anchor channel from peer {} due to insufficient available on-chain reserves.",
-                                                       counterparty_node_id,
-                                               );
+                                                               self.logger,
+                                                               "Rejecting inbound Anchor channel from peer {} due to insufficient available on-chain reserves.",
+                                                               counterparty_node_id,
+                                                       );
                                                        self.channel_manager
                                                                .force_close_without_broadcasting_txn(
@@ -1147,7 +1147,7 @@ where
                                        {
                                                log_debug!(self.logger,
-                                                               "Ignoring BumpTransactionEvent for channel {} due to trusted counterparty {}",
-                                                               channel_id, counterparty_node_id
-                                                       );
+                                                       "Ignoring BumpTransactionEvent for channel {} due to trusted counterparty {}",
+                                                       channel_id, counterparty_node_id
+                                               );
                                                return;
                                        }

@tnull tnull merged commit 2562f52 into lightningdevkit:main Jun 11, 2024
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3 participants