Beat [4/4]: implement `Consumer` in `chainWatcher` by yyforyongyu · Pull Request #9277 · lightningnetwork/lnd

yyforyongyu · 2024-11-18T06:45:04Z

This PR implements the Consumer interface in chainWatcher with necessary refactors.

TODOs

add a release note

Depends on

Beat [3/4]: prepare resolvers to handle the blockbeat #9276

NOTE: itest is fixed in the final PR

Beat itest [3/3]: fix all itest flakes #9260

This change is

coderabbitai · 2024-11-18T06:45:11Z

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Roasbeef · 2024-12-12T15:31:16Z

+
+	// If this is a taproot channel, before we proceed, we want to ensure
+	// that the expected funding output has confirmed on chain.
+	if c.cfg.chanState.IsPending && c.cfg.chanState.ChanType.IsTaproot() {


Posted the context in the other PR, not a bad idea to add more of that rationale here for future reviewers.

Roasbeef · 2024-12-12T15:46:25Z

+		}
+
+	// We have broadcast our commitment, and it is now confirmed onchain.
+	case closeInfo := <-c.cfg.ChainEvents.LocalUnilateralClosure:


Review note to make sure we remove the handling of these cases in the channelAttendant goroutine.

So this is still here: we handle all these events in two locations now. IIUC, we only want to handle them when received by the block beat.

At the bottom layer, we have two notifications,

RegisterBlockEpochNtfn which is the source of the block height used by blockbeat

``RegisterSpendNtfnwhich is the source of the funding spend used by thechainWatcher`

Observed from the itests, there is no gurantee of the event orders here - the chainWatcher may receive a blockbeat at height X, but only receives the spending notification at block X+1 or X-1, which means a close event may be sent from the chainWatcher to the ChannelArbitrator with one block offset, thus we need to catch the close event in two places - one in handleBlockbeat, in which we do a non-blocking read of the close event channels, and this should be most of the cases; the other one is done in channelAttendant, to catch the offset case to make sure we still process the close event.

Now, if the spending tx is notified at block X-1, we are fine as we want the close event to be there at block X. The bad case is the close event only arrives at block X+1, then we miss it at block X, which is why we added a change here 1200b75, where we always notify the spending tx before the block.

It doesn't completely solve the issue, as the above notification are sent in goroutines, and the receivers, aka subscribers, need to be aware of this possible race.

ziggie1984

Very close 👏

had some minor questions, PR looks dope 😺

ziggie1984 · 2024-12-12T10:29:02Z

+	// As a height hint, we'll try to use the opening height, but if the
+	// channel isn't yet open, then we'll use the height it was broadcast
+	// at. This may be an unconfirmed zero-conf channel.
+	heightHint := chanState.ShortChanID().BlockHeight


hmm for zeroconf channel channels this might still be garbage data because the shortchanid is like a random alias (not super random but still).

also from the ShortChanID method:

// If IsZeroConf(), then this will the "base" (very first) ALIAS scid // and the confirmed SCID will be stored in ConfirmedScid.

So I think we need to first theck for IsZeroConf first otherwise the blockeheight might not be 0 but wrong ?

i think they are handled below?

ahh gottya, kinda thought we are returning earlier. Maybe we cana structure the code so that if its zeroconf we fill out the chanID and return immediatly. and for the other case we proceed further. Otherwise we check the ShortChanID for zeroconf although it is not really needed.

ziggie1984 · 2024-12-12T11:12:59Z

+
+	// If this is a taproot channel, before we proceed, we want to ensure
+	// that the expected funding output has confirmed on chain.
+	if c.cfg.chanState.IsPending && c.cfg.chanState.ChanType.IsTaproot() {


response can be found here: #7346 (comment)

ziggie1984 · 2024-12-12T13:36:12Z

+	// TODO(Roasbeef): need to be able to ensure this only triggers
+	// on confirmation, to ensure if multiple txns are broadcast, we
+	// act on the one that's timestamped


cc @Roasbeef can you check if this TODO still needed here ?

ziggie1984 · 2024-12-12T15:47:33Z


+	// Perform a non-blocking read on the close events in case the channel
+	// is closed in this blockbeat.
+	c.receiveAndProcessCloseEvent()


Should we maybe check if the state is already in contractClosed so there is no need to call this again ?

yeah i like it, lemme try

building in a side branch, will push once it passes all the tests

ziggie1984 · 2024-12-12T15:49:01Z

 	}

+	// If this is a pending taproot channel, we need to register for a
+	// confirmation notification of the funding tx.


add a shorten explanation of the reasoning behind this as a comment from: https://github.com/lightningnetwork/lnd/pull/9277/files#r1864911793

i think you are referencing the wrong place? this is about keysend cannot be recognized in RegisterSpend

sorry correct: #7346 (comment)

This commit moves the creation of the spending notification from `Start` to `newChainWatcher` so we subscribe the spending event before handling the block, which is needed to properly handle the blockbeat.

To prepare for the blockbeat handler.

We now start notifying the blockbeat from the ChainArbitrator to the chainWatcher.

This commit adds the closing height to the logging and fixes a wrong height used in handling the breach event.

This commit adds a new method to enable us resending the blockbeat in `ChainArbitrator`, which is needed for the channel restore as the chain watcher and channel arbitrator are added after the start of the chain arbitrator.

To prepare the next commit where we would handle the event upon receiving a blockbeat.

We need to check `dispatched` before sending conf details, otherwise the channel `ntfn.Event.Confirmed` will be blocking, which is the leftover from lightningnetwork#9275.

ziggie1984

LGTM 🧘‍♂️ - pending CI run

Roasbeef

LGTM 🧜🏼

This is an oversight from addressing this commment: #9277 (comment) where we should focus on skipping the close events but not the resolvers.

This is an oversight from addressing this commment: lightningnetwork#9277 (comment) where we should focus on skipping the close events but not the resolvers.

This is an oversight from addressing this commment: #9277 (comment) where we should focus on skipping the close events but not the resolvers.

yyforyongyu added the no-itest label Nov 18, 2024

yyforyongyu force-pushed the yy-blockbeat-end branch from d2b0ffa to d863938 Compare November 18, 2024 11:31

yyforyongyu force-pushed the yy-blockbeat-finalize branch from ac8ce82 to a16b2d4 Compare November 18, 2024 11:34

yyforyongyu force-pushed the yy-blockbeat-end branch 2 times, most recently from 0ddd693 to 07631c0 Compare November 18, 2024 11:50

saubyk assigned yyforyongyu Nov 18, 2024

saubyk added this to the v0.19.0 milestone Nov 18, 2024

saubyk requested review from ellemouton and ziggie1984 November 18, 2024 14:55

yyforyongyu force-pushed the yy-blockbeat-finalize branch 3 times, most recently from c5f77e3 to 3456f2e Compare November 20, 2024 06:06

yyforyongyu force-pushed the yy-blockbeat-end branch from 07631c0 to 96474de Compare November 20, 2024 06:09

yyforyongyu force-pushed the yy-blockbeat-finalize branch from 3456f2e to 3d08b74 Compare November 20, 2024 06:21

yyforyongyu force-pushed the yy-blockbeat-end branch from 96474de to c7747a2 Compare November 20, 2024 07:14

yyforyongyu force-pushed the yy-blockbeat-finalize branch from 3d08b74 to e69cd41 Compare November 21, 2024 13:16

yyforyongyu force-pushed the yy-blockbeat-end branch from c7747a2 to a4f226a Compare November 21, 2024 13:24

yyforyongyu force-pushed the yy-blockbeat-finalize branch from e69cd41 to cdd805f Compare November 21, 2024 14:45

yyforyongyu force-pushed the yy-blockbeat-end branch from a4f226a to 9f740cc Compare November 21, 2024 14:45

Roasbeef requested changes Nov 22, 2024

View reviewed changes

Comment thread contractcourt/chain_watcher.go Outdated

Comment thread contractcourt/chain_watcher.go

Comment thread contractcourt/chain_watcher.go

Comment thread contractcourt/chain_arbitrator.go Outdated

Comment thread contractcourt/channel_arbitrator.go Outdated

yyforyongyu force-pushed the yy-blockbeat-finalize branch 2 times, most recently from 1e58126 to abbee3b Compare November 22, 2024 11:58

yyforyongyu force-pushed the yy-blockbeat-end branch from 9f740cc to 6bdb145 Compare November 22, 2024 14:40

yyforyongyu force-pushed the yy-blockbeat-finalize branch from abbee3b to aeafa63 Compare November 25, 2024 05:49

yyforyongyu force-pushed the yy-blockbeat-end branch 2 times, most recently from 0032fd7 to 5c9c6d0 Compare November 25, 2024 06:21

ellemouton removed their request for review November 27, 2024 08:54

yyforyongyu force-pushed the yy-blockbeat-finalize branch from 29521a1 to 7b19d5c Compare November 27, 2024 12:24

yyforyongyu force-pushed the yy-blockbeat-end branch from 5c9c6d0 to 54eaec8 Compare November 27, 2024 12:24

yyforyongyu force-pushed the yy-blockbeat-end branch from a890230 to 0882921 Compare December 12, 2024 11:50

Roasbeef reviewed Dec 12, 2024

View reviewed changes

ziggie1984 reviewed Dec 12, 2024

View reviewed changes

yyforyongyu changed the base branch from yy-blockbeat-finalize to yy-feature-blockbeat December 12, 2024 16:07

yyforyongyu force-pushed the yy-blockbeat-end branch from 0882921 to 4419530 Compare December 12, 2024 16:10

yyforyongyu added 8 commits December 13, 2024 18:01

contractcourt: implement Consumer on chainWatcher

e04a317

contractcourt: register spend notification during init

c82fd2c

This commit moves the creation of the spending notification from `Start` to `newChainWatcher` so we subscribe the spending event before handling the block, which is needed to properly handle the blockbeat.

contractcourt: add method handleCommitSpend

e3288bf

To prepare for the blockbeat handler.

contractcourt: handle blockbeat in chainWatcher

d78d567

contractcourt: notify blockbeat for chainWatcher

aaefe55

We now start notifying the blockbeat from the ChainArbitrator to the chainWatcher.

contractcourt: use close height instead of best height

5717719

This commit adds the closing height to the logging and fixes a wrong height used in handling the breach event.

multi: add new method ChainArbitrator.RedispatchBlockbeat

d0486f2

This commit adds a new method to enable us resending the blockbeat in `ChainArbitrator`, which is needed for the channel restore as the chain watcher and channel arbitrator are added after the start of the chain arbitrator.

contractcourt: add close event handlers in ChannelArbitrator

258c39d

To prepare the next commit where we would handle the event upon receiving a blockbeat.

yyforyongyu force-pushed the yy-feature-blockbeat branch from 6e3c1e4 to d4baf58 Compare December 13, 2024 11:09

yyforyongyu force-pushed the yy-blockbeat-end branch from 4419530 to 0339e40 Compare December 13, 2024 11:09

yyforyongyu added 4 commits December 13, 2024 20:22

contractcourt: process channel close event on new beat

cba204c

contractcourt: register conf notification once and cancel when confirmed

4106a90

chainntnfs: skip dispatched conf details

a715207

We need to check `dispatched` before sending conf details, otherwise the channel `ntfn.Event.Confirmed` will be blocking, which is the leftover from lightningnetwork#9275.

docs: add release notes for blockbeat series

03cb629

ziggie1984 approved these changes Dec 13, 2024

View reviewed changes

yyforyongyu force-pushed the yy-blockbeat-end branch from 0339e40 to 03cb629 Compare December 13, 2024 12:28

Roasbeef approved these changes Dec 13, 2024

View reviewed changes

Roasbeef merged commit 542b9c6 into lightningnetwork:yy-feature-blockbeat Dec 13, 2024

yyforyongyu deleted the yy-blockbeat-end branch December 15, 2024 23:12

yyforyongyu added a commit that referenced this pull request Dec 18, 2024

contractcourt: make sure launchResolvers is called on new blockbeat

953b103

This is an oversight from addressing this commment: #9277 (comment) where we should focus on skipping the close events but not the resolvers.

yyforyongyu added a commit that referenced this pull request Dec 20, 2024

contractcourt: make sure launchResolvers is called on new blockbeat

ffbf071

This is an oversight from addressing this commment: #9277 (comment) where we should focus on skipping the close events but not the resolvers.

yyforyongyu added a commit that referenced this pull request Dec 20, 2024

contractcourt: make sure launchResolvers is called on new blockbeat

3fcf560

This is an oversight from addressing this commment: #9277 (comment) where we should focus on skipping the close events but not the resolvers.

yyforyongyu added a commit that referenced this pull request Dec 20, 2024

contractcourt: make sure launchResolvers is called on new blockbeat

fecd5ac

This is an oversight from addressing this commment: #9277 (comment) where we should focus on skipping the close events but not the resolvers.

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yyforyongyu commented Nov 18, 2024 •

edited by ziggie1984

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