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

yyforyongyu · 2024-11-18T06:07:42Z

Depends on

Beat [2/4]: implement blockbeat #8894

NOTE: itest is fixed in the final PR

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

Turns out mounting blockbeat in ChannelArbitrator can be quite challenging (unit tests, itest, etc). This PR attempts to implement it in hopefully the least disruptive way - only chainWatcher implements Consumer, and the contract resolvers are kept stateless (in terms of blocks). The main changes are,

contract resolvers are refactored - the original Resolve method is broken into two steps: 1) Launch the resolver, which handles sending the sweep request, and 2) Resolve the resolver, which handles monitoring the spending of the output.
chainWatcher implements Consumer in the following PR.

Alternatives

The original attempt is to make the resolvers subscribe to a blockbeat chan, as implemented in #8717. The second attempt is to make the resolvers also blockbeat Consumer, as implemented here.

This third approach is chosen as 1) it greatly limits the scope otherwise a bigger refactor of channel arbitrator may be needed, and 2) the resolvers can be made stateless in terms of blocks, and be fully managed by the channel arbitrator. In other words, when a new block arrives, the channel arbitrator decides whether to launch the resolvers or not, so the resolvers themselves don't need this block info.

In fact, there are only two resolvers that subscribe to blocks, the incoming contest resolver, which uses block height to decide whether to give up resolving an expired incoming htlc; and the outgoing contest resolver, which uses the block height to choose to transform itself into a timeout resolver. IMO if we can remove the inheritance pattern used in contest resolver -> time/success resolver and manage to transform resolvers in channel arbitrator, we can further remove those two block subscriptions. As for now, we can leave them there as they have little impact on the block consumption order enforced by the blockbeat.

This change is

coderabbitai · 2024-11-18T06:07:49Z

Important

Review skipped

Auto reviews are limited to specific labels.

🏷️ Labels to auto review (1)

llm-review

Please check the settings in the CodeRabbit UI or the .coderabbit.yaml file in this repository. To trigger a single review, invoke the @coderabbitai review command.

You can disable this status message by setting the reviews.review_status to false in the CodeRabbit configuration file.

Thank you for using CodeRabbit. We offer it for free to the OSS community and would appreciate your support in helping us grow. If you find it useful, would you consider giving us a shout-out on your favorite social media?

❤️ Share

🪧 Tips

Chat

There are 3 ways to chat with CodeRabbit:

Review comments: Directly reply to a review comment made by CodeRabbit. Example:
- I pushed a fix in commit <commit_id>, please review it.
- Generate unit testing code for this file.
- Open a follow-up GitHub issue for this discussion.
Files and specific lines of code (under the "Files changed" tab): Tag @coderabbitai in a new review comment at the desired location with your query. Examples:
- @coderabbitai generate unit testing code for this file.
- @coderabbitai modularize this function.
PR comments: Tag @coderabbitai in a new PR comment to ask questions about the PR branch. For the best results, please provide a very specific query, as very limited context is provided in this mode. Examples:
- @coderabbitai gather interesting stats about this repository and render them as a table. Additionally, render a pie chart showing the language distribution in the codebase.
- @coderabbitai read src/utils.ts and generate unit testing code.
- @coderabbitai read the files in the src/scheduler package and generate a class diagram using mermaid and a README in the markdown format.
- @coderabbitai help me debug CodeRabbit configuration file.

Note: Be mindful of the bot's finite context window. It's strongly recommended to break down tasks such as reading entire modules into smaller chunks. For a focused discussion, use review comments to chat about specific files and their changes, instead of using the PR comments.

CodeRabbit Commands (Invoked using PR comments)

@coderabbitai pause to pause the reviews on a PR.
@coderabbitai resume to resume the paused reviews.
@coderabbitai review to trigger an incremental review. This is useful when automatic reviews are disabled for the repository.
@coderabbitai full review to do a full review from scratch and review all the files again.
@coderabbitai summary to regenerate the summary of the PR.
@coderabbitai generate docstrings to generate docstrings for this PR. (Experiment)
@coderabbitai resolve resolve all the CodeRabbit review comments.
@coderabbitai configuration to show the current CodeRabbit configuration for the repository.
@coderabbitai help to get help.

Other keywords and placeholders

Add @coderabbitai ignore anywhere in the PR description to prevent this PR from being reviewed.
Add @coderabbitai summary to generate the high-level summary at a specific location in the PR description.
Add @coderabbitai anywhere in the PR title to generate the title automatically.

CodeRabbit Configuration File (`.coderabbit.yaml`)

You can programmatically configure CodeRabbit by adding a .coderabbit.yaml file to the root of your repository.
Please see the configuration documentation for more information.
If your editor has YAML language server enabled, you can add the path at the top of this file to enable auto-completion and validation: # yaml-language-server: $schema=https://coderabbit.ai/integrations/schema.v2.json

Documentation and Community

Visit our Documentation for detailed information on how to use CodeRabbit.
Join our Discord Community to get help, request features, and share feedback.
Follow us on X/Twitter for updates and announcements.

github-actions · 2024-11-18T06:22:22Z

Pull reviewers stats

Stats of the last 30 days for lnd:

User	Total reviews	Time to review	Total comments
guggero 🥇	25 ▀▀▀▀	15h 44m	30 ▀▀
yyforyongyu 🥈	12 ▀▀	1d 8h 24m ▀	33 ▀▀▀
ellemouton 🥉	8 ▀	16h 51m	21 ▀▀
ziggie1984	5 ▀	16h 15m	9 ▀
ProofOfKeags	4 ▀	5d 4h 23m ▀▀	14 ▀
bhandras	3	1d 14h 22m ▀	2
dstadulis	3	1h 26m	5
Roasbeef	2	4d 13h 56m ▀▀	9 ▀
ViktorTigerstrom	2	2d 14h 26m ▀	5
alexbosworth	1	4d 11h 58m ▀▀	1
ffranr	1	2h 9m	0
bitromortac	1	16h 16m	0
saubyk	1	17h 10m	0

Roasbeef · 2024-11-22T00:21:38Z

IMO if we can remove the inheritance pattern used in contest resolver -> time/success resolver and manage to transform resolvers in channel arbitrator, we can further remove those two block subscriptions. As for now, we can leave them there as they have little impact on the block consumption order enforced by the blockbeat.

Minor point, it it isn't inheritance, it's composition, with the inner resolver replacing the outer one. Go technically doesn't have inheritance at all.

Roasbeef

I didn't review the first two PRs, so one thing I'm missing context on is: why dees Resolve need to split up in order to be incorporated into the new blockbeat architecture?

Is that that since we don't know which ones will be launched ahead of time, we can't set up the blockbeat consumer DAG upfront?

contractcourt/contract_resolver.go

contractcourt/htlc_timeout_resolver.go

contractcourt/htlc_success_resolver.go

Roasbeef · 2024-11-22T00:44:52Z

contractcourt/htlc_timeout_resolver.go

-		return err
-	}
-
-	h.outputIncubating = true


Same comment here re this state value. I do think it's possible to make the resolvers 100% stateless, by relying on chain notifications to figure out if something has been mined or not. The nursery might need to be queried distinctly though .

Yes! I also realized this after reviewing #9062. What's more, because the sweeper now handles re-offered inputs by first checking the db and mempool to grab the existing tx, it means it's safe to re-offer the same inputs during startup. And since deep down the nursery also uses the sweeper, it means we can easily make all the resolvers stateless.

Atm another usage of the outputIncubating is to decide whether we should resolve the stage one or stage two HTLC, which can also be changed to rely on chain notifications. So the changes would be something like,

subscribe the htlc tx spending at the very beginning when initializing the resolver

when Resolve it, if the htlc tx is already spent, subscribe to the output of the htlc tx

if the output is spent, we are done here

otherwise, wait for the spend to resolve the output spent.

Basically we just outsource the info provided by outputIncubating to chain notification, further simplify the resolvers here. The only part I'm not sure is for neutrino backend, since there's no mempool, it can only rely on the sweeper's store to decide whether an input is new or not, which means we may need to store more info there (currently only the txid).

I actually plan to do this after the blockbeat is in to limit the scope, rough idea is 1) refactor a bit to get rid of outputIncubating; 2) do a db migration to remove the outputIncubating (maybe not needed?); 3) completely remove the nursery! WDYT?

Basically we just outsource the info provided by outputIncubating to chain notification, further simplify the resolvers here. The only part I'm not sure is for neutrino backend, since there's no mempool, it can only rely on the sweeper's store to decide whether an input is new or not, which means we may need to store more info there (currently only the txid).

does our SpendRegistration also consider mempool spends, I thought for this we implemented waitForMempoolOrBlockSpend so I am not sure why the mempool is relevant here and could cause problems for neutrino.

why the mempool is relevant here and could cause problems for neutrino.

because of this,

lnd/sweep/sweeper.go

Line 1212 in fa309c9

state, rbfInfo := s.decideStateAndRBFInfo(input.input.OutPoint())

I think we should expand the sweeper store, probably before expanding it we should probably think of going straight to sql, because it is a very small subsystem regarding the datastructure.

contractcourt/commit_sweep_resolver.go

contractcourt/htlc_incoming_contest_resolver.go

contractcourt/htlc_timeout_resolver.go

contractcourt/channel_arbitrator.go

contractcourt/breach_resolver.go

Roasbeef · 2024-12-11T19:56:14Z

contractcourt/channel_arbitrator.go

@@ -3117,6 +3181,9 @@ func (c *ChannelArbitrator) handleBlockbeat(beat chainio.Blockbeat) error {
 		}
 	}

+	// Launch all active resolvers when a new blockbeat is received.


So with the new set of changes, the Launch method on the contest incoming resolver will check if the preimage is known or not. This makes sense to call each block as a mined transaction may have revealed the pre-image to the contest resolver

contractcourt/htlc_incoming_contest_resolver.go

Roasbeef · 2024-12-11T20:16:06Z

contractcourt/htlc_success_resolver.go


 	// Wait for the direct-preimage HTLC sweep tx to confirm.
+	//
+	// TODO(yy): use the result chan returned from `SweepInput`.


you mean the result chan can be blocking?

Roasbeef · 2024-12-11T20:16:19Z

contractcourt/htlc_success_resolver.go

-	// Once the transaction has received a sufficient number of
-	// confirmations, we'll mark ourselves as fully resolved and exit.
-	h.resolved = true
+	// TODO(yy): should also update the `RecoveredBalance` and


Done in the itest fix PR?

nope - more like a question since I don't know why it wasn't done before and need double check.

Roasbeef · 2024-12-11T20:21:32Z

contractcourt/htlc_timeout_resolver.go

+	// transaction that is signed using sighash SINGLE|ANYONECANPAY (the
+	// case for anchor type channels). In this case we can re-sign it and
+	// attach fees at will.
+	return h.htlcResolution.SignedTimeoutTx != nil &&


The success resolvers is the one that mutates the second level txn. It needs to add the preimage to the correct place in the witness.

Roasbeef

Reviewed 18 of 18 files at r1, all commit messages.
Reviewable status: all files reviewed, 46 unresolved discussions (waiting on @yyforyongyu and @ziggie1984)

ziggie1984

Very close 🙌

I still have one design consideration, I don't think we need to relaunch (calling the launch method for every blockbeat) for all resolvers other then the two contest resolvers.
Other than that this change looks good from my side.

ziggie1984 · 2024-12-10T13:27:58Z

contractcourt/htlc_timeout_resolver.go

+	// transaction that is signed using sighash SINGLE|ANYONECANPAY (the
+	// case for anchor type channels). In this case we can re-sign it and
+	// attach fees at will.
+	return h.htlcResolution.SignedTimeoutTx != nil &&


What I was just thinking we could add as a comment, that the TXID of this SignedTimeoutTx should not be used because it might be misleading.

ziggie1984 · 2024-12-10T13:48:01Z

contractcourt/htlc_timeout_resolver.go

-	// - HTLC1: nLocktime is 800000, CLTV delta is 80.
-	// - HTLC2: nLocktime is 800001, CLTV delta is 79.


are we now respecting the locktime when creating the sweep, or why can this be removed, iirc we still only group by relative deadline ?

that's what blockbeat solves here re the sync issue.

ziggie1984 · 2024-12-10T14:12:26Z

contractcourt/htlc_timeout_resolver.go

-		return err
-	}
-
-	h.outputIncubating = true


I think we should expand the sweeper store, probably before expanding it we should probably think of going straight to sql, because it is a very small subsystem regarding the datastructure.

contractcourt/htlc_timeout_resolver.go

contractcourt/anchor_resolver.go

ziggie1984 · 2024-12-11T18:22:01Z

contractcourt/commit_sweep_resolver.go

@@ -524,3 +371,181 @@ func (c *commitSweepResolver) initReport() {
 // A compile time assertion to ensure commitSweepResolver meets the
 // ContractResolver interface.
 var _ reportingContractResolver = (*commitSweepResolver)(nil)
+
+// Launch constructs a commit input and offers it to the sweeper.
+func (c *commitSweepResolver) Launch() error {


same here I think we can just lanch them once similar as proposed in the anchor resolver case. Then there would be no need for a launched boolean

but then how can we know whether a resolver is launched or not?

ziggie1984 · 2024-12-11T19:55:23Z

contractcourt/htlc_success_resolver.go

+
+// Launch creates an input based on the details of the incoming htlc resolution
+// and offers it to the sweeper.
+func (h *htlcSuccessResolver) Launch() error {


Also here I don't think we need to relaunch this resolver.

see comments above

contractcourt/htlc_timeout_resolver.go

ziggie1984 · 2024-12-11T21:39:51Z

contractcourt/htlc_incoming_contest_resolver.go

+	if h.isLaunched() {
+		h.log.Tracef("already launched")
+		return nil
+	}


I did not find where we ever set the launched variable to true for the two contest resolvers

was looking for markLaunched()

it embeds the success resolver as stated in the above comments NOTE: ...

ziggie1984 · 2024-12-11T21:45:41Z

contractcourt/channel_arbitrator.go

@@ -3117,6 +3181,9 @@ func (c *ChannelArbitrator) handleBlockbeat(beat chainio.Blockbeat) error {
 		}
 	}

+	// Launch all active resolvers when a new blockbeat is received.


yes I agree that we should always launch the 2 contest resolver, for the other resolvers it does imo not really make sense because they will already be marked as launched.

We now put the outpoint in the resolvers's logging so it's easier to debug.

This commit adds a few helper methods to decide how the htlc output should be spent.

This commit is a pure refactor in which moves the sweep handling logic into the new methods.

This commit refactors the `Resolve` method by adding two resolver handlers to handle waiting for spending confirmations.

This commit adds new methods to handle making sweep requests based on the spending path used by the outgoing htlc output.

This commit adds checkpoint methods in `htlcTimeoutResolver`, which are similar to those used in `htlcSuccessResolver`.

This commit adds more methods to handle resolving the spending of the output based on different spending paths.

We will use this and its following commits to break the original `Resolve` methods into two parts - the first part is moved to a new method `Launch`, which handles sending a sweep request to the sweeper. The second part remains in `Resolve`, which is mainly waiting for a spending tx. Breach resolver currently doesn't do anything in its `Launch` since the sweeping of justice outputs are not handled by the sweeper yet.

This commit breaks the `Resolve` into two parts - the first part is moved into a `Launch` method that handles sending sweep requests, and the second part remains in `Resolve` which handles waiting for the spend. Since we are using both utxo nursery and sweeper at the same time, to make sure this change doesn't break the existing behavior, we implement the `Launch` as following, - zero-fee htlc - handled by the sweeper - direct output from the remote commit - handled by the sweeper - legacy htlc - handled by the utxo nursery

When calling `NotifyExitHopHtlc` it is allowed to pass a chan to subscribe to the HTLC's resolution when it's settled. However, this method will also return immediately if there's already a resolution, which means it behaves like a notifier and a getter. If the caller decides to only use the getter to do a non-blocking lookup, it can pass a nil subscriber chan to bypass the notification.

A minor refactor is done to support implementing `Launch`.

This commit makes `resolved` an atomic bool to avoid data race. This field is now defined in `contractResolverKit` to avoid code duplication.

In this commit, we break the old `launchResolvers` into two steps - step one is to launch the resolvers synchronously, and step two is to actually waiting for the resolvers to be resolved. This is critical as in the following commit we will require the resolvers to be launched at the same blockbeat when a force close event is sent by the chain watcher.

We need to offer the outgoing htlc one block earlier to make sure when the expiry height hits, the sweeper will not miss sweeping it in the same block. This also means the outgoing contest resolver now only does one thing - watch for preimage spend till height expiry-1, which can easily be moved into the timeout resolver instead in the future.

ziggie1984

LGTM

Roasbeef

LGTM 🏆

yyforyongyu self-assigned this Nov 18, 2024

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

yyforyongyu mentioned this pull request Nov 18, 2024

Beat [4/4]: implement Consumer in chainWatcher #9277

Merged

1 task

yyforyongyu added the no-itest label Nov 18, 2024

yyforyongyu force-pushed the yy-blockbeat branch from 763bfc7 to d7b0d2f Compare November 18, 2024 11:34

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

saubyk requested review from ziggie1984 and ellemouton November 18, 2024 14:53

yyforyongyu force-pushed the yy-blockbeat branch 4 times, most recently from 02cebbb to e40d7aa Compare November 19, 2024 13:28

yyforyongyu force-pushed the yy-blockbeat-finalize branch from a16b2d4 to ae69b98 Compare November 19, 2024 13:52

yyforyongyu force-pushed the yy-blockbeat branch from e40d7aa to 736edda Compare November 19, 2024 23:27

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

yyforyongyu force-pushed the yy-blockbeat branch 2 times, most recently from 1e17c5c to 9ab2e53 Compare November 21, 2024 13:00

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

yyforyongyu added the no-changelog label Nov 21, 2024

Base automatically changed from yy-blockbeat to yy-feature-blockbeat November 21, 2024 14:41

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

yyforyongyu force-pushed the yy-feature-blockbeat branch from 9ab2e53 to 9ed2522 Compare November 21, 2024 14:49

Roasbeef requested changes Nov 22, 2024

View reviewed changes

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-finalize branch from ef85fb5 to cebad6d Compare December 10, 2024 07:14

Roasbeef reviewed Dec 11, 2024

View reviewed changes

Roasbeef requested a review from ziggie1984 December 11, 2024 20:23

Roasbeef reviewed Dec 11, 2024

View reviewed changes

ziggie1984 reviewed Dec 11, 2024

View reviewed changes

yyforyongyu added 8 commits December 12, 2024 17:50

contractcourt: add verbose logging in resolvers

82d77bb

We now put the outpoint in the resolvers's logging so it's easier to debug.

contractcourt: add spend path helpers in timeout/success resolver

3cb48a0

This commit adds a few helper methods to decide how the htlc output should be spent.

contractcourt: add sweep senders in htlcSuccessResolver

10d9544

This commit is a pure refactor in which moves the sweep handling logic into the new methods.

contractcourt: add resolver handlers in htlcSuccessResolver

693287f

This commit refactors the `Resolve` method by adding two resolver handlers to handle waiting for spending confirmations.

contractcourt: remove redundant return value in claimCleanUp

fe29961

contractcourt: add sweep senders in htlcTimeoutResolver

7e0623c

This commit adds new methods to handle making sweep requests based on the spending path used by the outgoing htlc output.

contractcourt: add methods to checkpoint states

066d351

This commit adds checkpoint methods in `htlcTimeoutResolver`, which are similar to those used in `htlcSuccessResolver`.

contractcourt: add resolve handlers in htlcTimeoutResolver

c108487

This commit adds more methods to handle resolving the spending of the output based on different spending paths.

yyforyongyu force-pushed the yy-feature-blockbeat branch from 5f37d93 to 1643508 Compare December 12, 2024 10:44

yyforyongyu added 11 commits December 12, 2024 18:48

contractcourt: add Launch method to commit resolver

629c037

contractcourt: add Launch method to incoming contest resolver

fe4ab4e

A minor refactor is done to support implementing `Launch`.

contractcourt: add Launch method to outgoing contest resolver

dbfe5df

contractcourt: fix concurrent access to resolved

1c8cbc8

This commit makes `resolved` an atomic bool to avoid data race. This field is now defined in `contractResolverKit` to avoid code duplication.

contractcourt: fix concurrent access to launched

b6c4dd9

yyforyongyu force-pushed the yy-blockbeat-finalize branch from cebad6d to 7751b1b Compare December 12, 2024 10:57

ziggie1984 approved these changes Dec 12, 2024

View reviewed changes

Roasbeef approved these changes Dec 12, 2024

View reviewed changes

Roasbeef merged commit 6e3c1e4 into yy-feature-blockbeat Dec 12, 2024
15 of 19 checks passed

yyforyongyu deleted the yy-blockbeat-finalize branch December 12, 2024 16:07

		// - HTLC1: nLocktime is 800000, CLTV delta is 80.
		// - HTLC2: nLocktime is 800001, CLTV delta is 79.

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

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

Conversation

yyforyongyu commented Nov 18, 2024 • edited by Roasbeef Loading

Alternatives

coderabbitai bot commented Nov 18, 2024 • edited Loading

Review skipped

Chat

CodeRabbit Commands (Invoked using PR comments)

Other keywords and placeholders

CodeRabbit Configuration File (.coderabbit.yaml)

Documentation and Community

github-actions bot commented Nov 18, 2024

Pull reviewers stats

Roasbeef commented Nov 22, 2024

Roasbeef left a comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Roasbeef left a comment

Choose a reason for hiding this comment

ziggie1984 left a comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

ziggie1984 Dec 11, 2024 • edited Loading

Choose a reason for hiding this comment

ziggie1984 left a comment

Choose a reason for hiding this comment

Roasbeef left a comment

Choose a reason for hiding this comment

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

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

yyforyongyu commented Nov 18, 2024 •

edited by Roasbeef

Loading

coderabbitai bot commented Nov 18, 2024 •

edited

Loading

CodeRabbit Configuration File (`.coderabbit.yaml`)

ziggie1984 Dec 11, 2024 •

edited

Loading