graph: refactor `graph.Builder` update handling #9476

ellemouton · 2025-02-05T08:06:15Z

Part of #9475

Some minor refactoring in the graph.Builder. The main purpose of which is to separate out the funding transaction validation logic so that reviewing the removal of that later on will be easier.

coderabbitai · 2025-02-05T08:06:22Z

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bhandras

Straightforward changes, love the small PR! Just one question, otherwise look good!

graph/builder.go

bhandras

LGTM 🥇

yyforyongyu

Love it! Left some questions and suggestions (also timed myself a bit, it took roughly 25min to review, and most of the time is taken on the decomposition part).

graph/builder.go

yyforyongyu · 2025-02-06T08:34:23Z

graph/builder.go

+	op ...batch.SchedulerOption) error {
+
+	select {
+	case <-b.quit:


I don't think this select is necessary? If it quits shouldn't we make sure the data are persisted on disk first?

so this just keeps the logic mostly as it stands today today. Since today, the AddEdge/AddChannel/UpdateEdge will abort if the quit channel is closed.

however, this did make me realise that this is not exactly as things stand today since today we will abort at any point if the quit channel is closed (since the handling is spun off in a go routine) and not we only check quickly at the start but then still do the persistence until completion.

So just to keep this PR a pure refactor, im going to revert some of the changes so that this still aborts as soon as the quit channel is closed.

Then in a follow up, we can actually change the logic to: wait for the data to be persisted & then any cancellation of these calls should be determined not by the builder's quit channel but instead by the caller's (of AddChan/Node/Update) passed context. sound good?

yyforyongyu · 2025-02-06T08:43:39Z

graph/builder.go

-	case <-b.quit:
-		return ErrGraphBuilderShuttingDown
-	}
+	return b.handleNetworkUpdate(edge, op...)


Very nice decomposition! This gets me to think, what's the point of creating a handleNetworkUpdate, when it takes a msg any, do a type switch there, and call the corresponding addNode/addEdge/updateEdge, when we already know what we want here? I think we can directly call addEdge inside AddEdge etc. Then handleNetworkUpdate can just be handleTopologyChange, wdyt?

yeah mostly agree - the reason for this was just so we dont have to repeat the code that is constant across all 3 calls. namely the error handling (see the if IsError(err, ErrIgnored, ErrOutdated) { check above) and then the topology notifications.

So can remove this but then we are repeating that code in each handler.

(see the other comment btw)

yyforyongyu · 2025-02-06T08:45:11Z

graph/builder.go

-	}
+	b.wg.Add(1)
+	go func() {
+		defer b.wg.Done()


Any reason we want this to be async?

just keeping the logic as close to today's as possible here since today this part is async. Perhaps doing the topology notifications takes a while, for example. Callers of AddNode/Channel should only be blocked on the DB writes I think

N/A now as i've reverted to some of the previous logic (but this part still remains async there)

The `netann` package is a more appropriate place for this code to live. Also, once the funding transaction code is moved out of the `graph.Builder`, then no `lnwire` validation will occur in the `graph` package.

In this commit, we remove the `processUpdate` method which handles each announement type (node, channel, channel update) in a separate switch case. Each of these cases currently has a non-trivial amount of code. This commit creates separate methods for each message type we want to handle instead. This removes a level of indentation and will make things easier to review when we start editing the code for each handler.

ellemouton

Thanks for the review ya'll!

I realised that for this to remain a pure refactor PR, some of the initial async code needed to be added back just to keep the behaviour where: if the Builder's quit channel is closed, then the public calls (AddChan/Node/Update) will continue to error out.

I can create a follow up PR where we actually change this behaviour to: continue till completion or error if the caller's context is cancelled.

Let me know what you think of this and the fixup commit, and then I'll squash it in if everyone is happy with this

ellemouton · 2025-02-07T05:24:33Z

graph/builder.go

-	}
+	b.wg.Add(1)
+	go func() {
+		defer b.wg.Done()


just keeping the logic as close to today's as possible here since today this part is async. Perhaps doing the topology notifications takes a while, for example. Callers of AddNode/Channel should only be blocked on the DB writes I think

ellemouton · 2025-02-07T05:29:19Z

graph/builder.go

+	op ...batch.SchedulerOption) error {
+
+	select {
+	case <-b.quit:


so this just keeps the logic mostly as it stands today today. Since today, the AddEdge/AddChannel/UpdateEdge will abort if the quit channel is closed.

however, this did make me realise that this is not exactly as things stand today since today we will abort at any point if the quit channel is closed (since the handling is spun off in a go routine) and not we only check quickly at the start but then still do the persistence until completion.

So just to keep this PR a pure refactor, im going to revert some of the changes so that this still aborts as soon as the quit channel is closed.

Then in a follow up, we can actually change the logic to: wait for the data to be persisted & then any cancellation of these calls should be determined not by the builder's quit channel but instead by the caller's (of AddChan/Node/Update) passed context. sound good?

ellemouton · 2025-02-07T05:29:45Z

graph/builder.go

-	case <-b.quit:
-		return ErrGraphBuilderShuttingDown
-	}
+	return b.handleNetworkUpdate(edge, op...)


yeah mostly agree - the reason for this was just so we dont have to repeat the code that is constant across all 3 calls. namely the error handling (see the if IsError(err, ErrIgnored, ErrOutdated) { check above) and then the topology notifications.

So can remove this but then we are repeating that code in each handler.

ellemouton · 2025-02-07T05:47:43Z

graph/builder.go

-	case <-b.quit:
-		return ErrGraphBuilderShuttingDown
-	}
+	return b.handleNetworkUpdate(edge, op...)


(see the other comment btw)

ellemouton · 2025-02-07T05:48:04Z

graph/builder.go

-	}
+	b.wg.Add(1)
+	go func() {
+		defer b.wg.Done()


N/A now as i've reverted to some of the previous logic (but this part still remains async there)

ellemouton · 2025-02-07T05:52:55Z

@bhandras - re-requesting from you just to get your thoughts on the fixup commit (see comment above)

bhandras

LGTM ✨

graph/builder.go

yyforyongyu · 2025-02-07T09:53:10Z

Pending linter fix and the squash, other good to go.

The point of the `graph.Builder`'s `networkHandler` goroutine is to ensure that certain requests are handled in a synchronous fashion. However, any requests received on the `networkUpdates` channel, are currently immediately handled in a goroutine which calls `handleNetworkUpdate` which calls `processUpdate` before doing topology notifications. In other words, there is no reason for these `networkUpdates` to be handled in the `networkHandler` since they are always handled asynchronously anyways. This design is most likely due to the fact that originally the gossiper and graph builder code lived in the same system and so the pattern was copied across. So in this commit, we just remove the complexity. The only part we need to spin off in a goroutine is the topology notifications.

This logic used to be handled by the router. Update to reflect new owner.

yyforyongyu

LGTM 🌹

ellemouton added code health Related to code commenting, refactoring, and other non-behaviour improvements graph refactoring labels Feb 5, 2025

ellemouton self-assigned this Feb 5, 2025

ellemouton requested review from bhandras and yyforyongyu February 5, 2025 08:49

ellemouton mentioned this pull request Feb 5, 2025

discovery+graph: move funding tx validation to the gossiper #9478

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ellemouton added 2 commits February 7, 2025 07:30

multi: move node ann validation code to netann pkg

1974903

The `netann` package is a more appropriate place for this code to live. Also, once the funding transaction code is moved out of the `graph.Builder`, then no `lnwire` validation will occur in the `graph` package.

ellemouton force-pushed the graph1 branch from bd5cad3 to a82de45 Compare February 7, 2025 05:45

ellemouton commented Feb 7, 2025

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ellemouton requested review from yyforyongyu and bhandras February 7, 2025 05:51

bhandras approved these changes Feb 7, 2025

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ellemouton added 3 commits February 7, 2025 13:01

graph: rename routerStats to builderStats

6169b47

This logic used to be handled by the router. Update to reflect new owner.

docs: update release notes

a86a5ed

ellemouton force-pushed the graph1 branch from a82de45 to a86a5ed Compare February 7, 2025 11:01

yyforyongyu approved these changes Feb 7, 2025

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guggero merged commit 3c0350e into lightningnetwork:master Feb 7, 2025
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ellemouton deleted the graph1 branch February 7, 2025 13:24

This was referenced Feb 10, 2025

Graph Abstraction & Gossiper->to->DB stack clean-up with Remote Graph & Gossip 1.75 projects in mind #9494

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graph: ensure topology subscriber handling and network msg handling is synchronous #9515

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graph: refactor graph.Builder update handling #9476

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graph: refactor `graph.Builder` update handling #9476

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