localchans: recreate missing edge if not found

[JssDWt]

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Change Description

Description of change / link to associated issue.If a node contains a channel, but doesn't have a corresponding edge in the graph database, updating the channel policy would fail. In this commit the edge is recreated if the channel exists. This ensures a node can recover from a missing edge in the graph database by calling updatechanpolicy.

Alternative for https://github.com/lightningnetwork/lnd/pull/8768, namely option 2 in https://github.com/lightningnetwork/lnd/pull/8768#issuecomment-2143799767 Partially fixes https://github.com/lightningnetwork/lnd/issues/7261 by allowing to recreate the edge by calling updatechanpolicy.

Steps to Test

• Create a node that has a channel with a missing edge
• Calling getchaninfo on this channel will fail
• Call updatechanpolicy on this channel
• Calling getchaninfo on this channel should succeed

I'm not sure how to create an integration test where I can modify the graph database to delete an edge in order to test this. Please advise.

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[guggero]

Release notes need to be moved to the v0.18.1 file.

[yyforyongyu]

Maybe it's related to this?

[ziggie1984]

Maybe it's related to https://github.com/lightningnetwork/lnd/issues/8870#issuecomment-2192464477?

Hmm I don't think so, not having the edge available means somehow that our own ChanAnnouncment didn't got through? Not receiving the node announcment would just leave us with a NodeAnnouncement Shell, we add during adding the edge to the db.

[ziggie1984]

Concept Ack from my side as well, I think it's the best way to fix broken channels suffering from the Edge not Found problem. I think we still have not traced down the origin of the problem, this gives us at least the possibility to mitigate the problem.

[JssDWt]

Sorry for letting this sit for so long. Updated with your feedback now @yyforyongyu

[ziggie1984]

what about passing the graph db as a config to the localchan_manager, so that we can when recreating the edge just call AddChannelEdge and short-circuit all the other stuff which is done in the gossiper ? Later during the ChanUpdate (PropagateChanPolicyUpdate) all the necessary stuff is done (adding the update to the Topology etc.).

It's a mitigation to a unknown bug anyways which we will find as soon as we improved logging in the gossiper.

[JssDWt]

Handled most comments. Still have to create a test.

[JssDWt]

Added a test for createEdge

[JssDWt]

Now also added a test to the UpdatePolicy function

[JssDWt]

Handled Ziggie's comments.

If this gets a thumbs up, we'll try it out in production to see whether it helps with our edge not found issues.

[ziggie1984]

Awesome job @JssDWt 🎉, thanks for fixing this in LND. Just a little style nit.

I will approve this PR once you give us feedback how your local testing went but it's gtg from my side.

[ziggie1984]

@JssDWt have you tested already, because we are planning to ship it in 18.3 ?

[JssDWt]

@ziggie1984 you can't ship it with 0.18.3. There was a crash. I'm afk for the next week, I'll look at it next week.

[saubyk]

@ziggie1984 you can't ship it with 0.18.3. There was a crash. I'm afk for the next week, I'll look at it next week.

Moved to 0.19

[JssDWt]

Added a fix for a crash, because SchedulerOptions were nil.

[JssDWt]

Rebased

[ziggie1984]

Just for general information this was the problem:

AddEdge: func(edge *models.ChannelEdgeInfo) error {
			return s.chanRouter.AddEdge(edge, nil)}

by accident we provided a nil for the SchedulerOptions

now it's fixed, we don't test db interaction in the unit-test case.

AddEdge: func(edge *models.ChannelEdgeInfo) error {
			return s.graphBuilder.AddEdge(edge)
		},

However I think because this happened lets add a nil checke here:

for _, f := range op {
         if f != nil{
		f(r)
         }
	                        }

better safe than sorry.

[JssDWt]

Noting that during the rebase I had to replace chanRouter with graphBuilder here.

[JssDWt]

However I think because this happened lets add a nil checke here:

for _, f := range op {
         if f != nil{
		f(r)
         }
	                        }

better safe than sorry.

Added this in this PR

[JssDWt]

Fixed a bug where the timestamp was not set, so the policy wouldn't be added.

And rebased.

[JssDWt]

Added a commit that ensures the policy is also recreated if the edge exists, but only not the policy.

[ziggie1984]

Looking good, waiting your final test and hope we can get this thing merged then.

[ziggie1984]

Will approve as soon as @JssDWt reports back that this actually fixes the problem of missing edges, so it is only on hold because we cannot easily reproduce missing edgeinfo in a db testing it in an itest.

[guggero]

Will approve as soon as @JssDWt reports back that this actually fixes the problem of missing edges, so it is only on hold because we cannot easily reproduce missing edgeinfo in a db testing it in an itest.

Ah, sorry. Wasn't sure if the latest push contained those (probably should've checked :sweat_smile:).

[lightninglabs-deploy]

@jssdwt, remember to re-request review from reviewers when ready

[JssDWt]

Added comments that the ForAllOutgoingChannels function may invoke the callback with a nil channel policy. Also rebased.

[ziggie1984]

Ok let's not change too much right now let's do the following:

1. We cannot just log a warning in the edge=nil case, with the combination of createMissingEdge we would attempt in the worst case scenario to readd an edge => so let's return an error here, because that should never be the case.

2. In updateEdge => use a NON-Pointer for the *models.ChannelEdgePolicy

3. remove this form updateEdge: if edge == nil { _, edge, err = r.createEdge(channel, time.Now()) if err != nil { return nil, err } }

We now check the policy so I don't think there is a need for the above.

Then we should be good to go

[JssDWt]

I undid the tryout commit.

2. In updateEdge => use a NON-Pointer for the *models.ChannelEdgePolicy

This we can't do, because that wouldn't update the edge outside the updateEdge function.

1. We cannot just log a warning in the edge=nil case, with the combination of createMissingEdge we would attempt in the worst case scenario to readd an edge => so let's return an error here, because that should never be the case.
2. remove this form updateEdge: if edge == nil { _, edge, err = r.createEdge(channel, time.Now()) if err != nil { return nil, err } }

So this basically means revert commit 7d9d100e94cab9fc5adce139fe2a9a8b3dd77538 correct?

That would also address this comment: https://github.com/lightningnetwork/lnd/pull/8805#discussion_r1845605281

[ziggie1984]

This we can't do, because that wouldn't update the edge outside the updateEdge function.

I am not sure I understand, I am talking about the func (r *Manager) updateEdge(tx kvdb.RTx, chanPoint wire.OutPoint, function, which is only used 2 times and also returns the specified edge so we can use the return value here, as we currently do anyways ?