lnwallet/test: fix flaky neutrino reorg sync timeout

[ziggie1984]

Summary

• Fix a goroutine leak in waitForWalletSync: time.Tick inside the
  poll loop leaked a new goroutine on every iteration (~1500 over 5
  reorg cycles), adding system load that caused the 30s timeout to fire
  spuriously, particularly on postgres backends where block-processing
  writes carry more overhead.
• Raise the timeout from 30s to 2 minutes to give the neutrino P2P
  layer and the address-manager transaction walk enough headroom under
  load.
• Improve timeout error messages to identify which sync layer was stuck:
  • Layer 1 (header/P2P lag): ChainIO.GetBestBlock has not caught
    up to the miner tip — neutrino is still fetching headers.
  • Layer 2 (transaction-walk lag): heights matched but IsSynced()
    never returned true — the chain-sync notification or the
    address-manager DB write (undo+redo on reorg) did not complete in
    time.
• Add a detailed doc comment to waitForWalletSync explaining the
  three-stage sync pipeline (header sync → compact-filter/block fetch →
  transaction walk + DB write) and why each stage matters, so a future
  timeout can be diagnosed from the error message alone.

Test plan

• make unit pkg=github.com/lightningnetwork/lnd/lnwallet/test/neutrino case=TestLightningWallet passes consistently
• No new goroutine leaks (single NewTicker with deferred Stop)

[gemini-code-assist]

Summary of Changes

Hello, 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 flakiness in neutrino reorg sync tests by refining the waitForWalletSync function. It eliminates a goroutine leak, extends the synchronization timeout to prevent spurious failures under load, and provides more granular error messages to pinpoint the exact stage of a sync timeout. These changes aim to improve the robustness and diagnosability of wallet synchronization in test environments.

Highlights

• Goroutine Leak Fix: Addressed a goroutine leak in waitForWalletSync by replacing time.Tick with time.NewTicker and ensuring proper cleanup with defer ticker.Stop().
• Timeout Extension: Increased the waitForWalletSync timeout from 30 seconds to 2 minutes to accommodate slower sync operations, especially under load or with postgres backends.
• Enhanced Error Reporting: Improved timeout error messages to clearly indicate whether the sync failure occurred during header synchronization (Layer 1) or full wallet processing (Layer 2), aiding in quicker diagnosis.
• Detailed Documentation: Added a comprehensive doc comment to waitForWalletSync explaining the multi-stage sync pipeline (header sync, compact-filter/block fetch, transaction walk + DB write) for easier future diagnosis.

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[github-actions]

🔴 PR Severity: CRITICAL

Classified by file path | 1 file | 85 lines changed

🔴 Critical (1 file)

• lnwallet/test/test_interface.go - Falls under lnwallet/*: wallet operations test infrastructure

Analysis

This PR modifies lnwallet/test/test_interface.go, which resides in the lnwallet/ package tree. Per classification rules, all files under lnwallet/* are CRITICAL as this package covers wallet operations, channel funding, signing, and commitment transactions.

Note: The changed file is in a test/ subdirectory of lnwallet and carries the flake fix label, indicating it is test infrastructure rather than production wallet logic. The file does not match the explicit test-exclusion patterns (*_test.go, itest/*, lntest/*), so it inherits the CRITICAL rating from its parent package path. If this change is purely test scaffolding with no production impact, consider adding severity-override-low or severity-override-medium to reflect the actual risk.

No severity bump triggers were met (1 file changed, 85 lines total).

---

_{To override, add a severity-override-{critical,high,medium,low} label.}

[ziggie1984]

overwriting this to medium since it only touches a test.

[gemini-code-assist]

Code Review

This pull request refactors the waitForWalletSync function to enhance its robustness and diagnostic capabilities. Key changes include extending the timeout duration, preventing goroutine leaks by using time.NewTicker, and providing more detailed error messages that distinguish between header sync and full wallet sync failures. The function also receives extensive documentation explaining its two-layer synchronization process. A minor style guide violation was noted, requiring a blank line between case stanzas in the select statement for improved readability.

[gemini-code-assist]

According to the style guide, there should be spacing between case stanzas in select statements for better readability. Please add a blank line before case <-ticker.C:.

				bestHeight)

		case <-ticker.C:

References

1. The style guide requires spacing between case and select stanzas to improve code readability. The provided example for switch statements demonstrates this with blank lines between cases. ^(link)

[lightninglabs-deploy]

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

[yyforyongyu]

Pending linter fix, otherwise LGTM

[github-actions]

⚠️ Severity changed: severity-critical → severity-medium (files changed since last classification)

🟡 PR Severity: MEDIUM

Override applied | 1 file | 87 lines changed

🟡 Override (severity-override-medium present)

• A severity-override-medium label was found on this PR — automated classification is skipped and the override level is used directly.

Analysis

This PR carries a severity-override-medium label, which takes precedence over any automated classification. The previously applied label (severity-critical) has been replaced with severity-medium to match the override.

No file-by-file classification was performed, as the override is authoritative.

---

_{To change the override, replace the severity-override-medium label with severity-override-{critical,high,medium,low}.}
<!-- pr-severity-bot -->

[yyforyongyu]

LGTM 🔨 - Gonna merge given that this only touches test files and has low severity.