netann: fix race condition in TestChanStatusManagerStateMachine

[ellemouton]

Fix a race condition in the "add new channels" subtest where the manager's status sampling ticker could fire between adding channel edge policies and marking channels as active in the switch.

This race caused the manager to:

1. Discover new channels with enabled edge policies
2. Check if they're active (they weren't yet)
3. Schedule and send a disable update

The fix reorders the operations to mark channels active before adding edge policies, ensuring the manager always sees them as active.

FIxes a flake found in this build

[gemini-code-assist]

Summary of Changes

Hello @ellemouton, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request resolves a race condition identified in the TestChanStatusManagerStateMachine test. The issue arose when the channel status manager's sampling ticker would fire at an inopportune moment, causing newly added channels to be incorrectly perceived as inactive and subsequently scheduled for disable updates. The solution reorders the sequence of operations to guarantee that channels are marked active prior to the addition of their edge policies, thereby eliminating the timing window that led to the flakiness.

Highlights

• Race Condition Fix: Addressed a race condition in the TestChanStatusManagerStateMachine test where the channel status manager could incorrectly mark newly added channels as inactive due to a timing issue between policy addition and activation.
• Operational Reordering: The fix involves reordering the operations to ensure channels are marked active before their edge policies are added, preventing premature disable updates and resolving a test flake.

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[gemini-code-assist]

Code Review

This pull request fixes a race condition in the TestChanStatusManagerStateMachine's "add new channels" subtest. The change correctly reorders operations by marking new channels as active before adding their edge policies to the graph. This prevents a scenario where the manager's ticker could find a new, enabled channel that is not yet active, leading to an incorrect disable update. The fix is logical, well-explained in the updated comment, and should resolve the test flakiness.

[ellemouton]

the itest flake cannot possibly be linked to this diff since this only touches unit test code

[yyforyongyu]

Thanks a lot for taking a look!!

So the flake comes from this line,

lnd/netann/chan_status_manager.go

Lines 536 to 537 in 3d7ff86

	if m.cfg.IsChannelActive(chanID) {
	continue

which requires the channel to be found here,

lnd/netann/chan_status_manager_test.go

Line 333 in 3d7ff86

IsChannelActive: htlcSwitch.HasActiveLink,

which checks the map here,

lnd/netann/chan_status_manager_test.go

Line 299 in 3d7ff86

active, ok := s.isActive[chanID]

which is added here via markActive,

lnd/netann/chan_status_manager_test.go

Line 394 in 3d7ff86

h.htlcSwitch.SetStatus(chanID, true)

Now when the ticker fires, inside markPendingInactiveChannels, it gets a list of channels to look at from,

lnd/netann/chan_status_manager.go

Line 508 in 3d7ff86

channels, err := m.fetchChannels()

which is the g.chans() here,

lnd/netann/chan_status_manager_test.go

Line 160 in 3d7ff86

return g.chans(), nil

which is added here in the test,

lnd/netann/chan_status_manager_test.go

Lines 742 to 744 in 3d7ff86

	for _, c := range newChans {
	h.graph.addChannel(c)
	}

So I think to completely fix the flake, we need to call h.markActive before the above loop where we call h.graph.addChannel?

[lightninglabs-deploy]

@ziggie1984: review reminder
@ellemouton, remember to re-request review from reviewers when ready