(Requires Audit) PLEX-2473 LogPoller Fix Reorg Handing on Replay (Part 1)

[dhaidashenko]

TestCase that were previously failing:

1. LogPoller processes blocks to block 11
2. Reorg replaces block 11 with a new block (some additional blocks may be added on top of it)
3. Replay is initiated from block below 11.

Expected behaviour:

1. LogPoller must replace reorged block 11 with a new data.
2. DB must not contain at any point logs from both old and new block 11.
3. Finality Violation must not occur, since chain did not violate finality depth.

Supports: #356

[github-actions]

⚠️ API Diff Results - Breaking changes detected

📦 Module: github-com-smartcontractkit-chainlink-evm

🔴 Breaking Changes (2)

pkg/logpoller.(*logPoller) (1)

• PollAndSaveLogs — Type changed:

func(
  context.Context, 
  - int64
  + int64, 
  + bool
)

pkg/logpoller.LogPollerTest (1)

• PollAndSaveLogs — Type changed:

func(
  context.Context, 
  - int64
  + int64, 
  + bool
)

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[Copilot]

Pull request overview

This PR fixes reorg (reorganization) handling in the LogPoller when replay operations encounter blocks that have been reorged. The core issue was that when LogPoller processed blocks up to block N, then a reorg replaced block N, and a replay was initiated from a block below N, the old and new versions of block N could coexist in the database, or a false finality violation could occur.

Changes:

• Added isReplay boolean parameter to PollAndSaveLogs method and related internal functions to enable special reorg detection logic during replay operations
• Extracted headerByNumber helper method to reduce code duplication when fetching block headers from RPC
• Enhanced getCurrentBlockMaybeHandleReorg to detect reorgs during replay by checking if current and latest blocks in DB match their RPC counterparts
• Refactored reorg handling logic into a new handleReorg method for better code organization
• Added comprehensive test case covering three scenarios: replay immediately after reorg, replay a few blocks after reorg, and replay after reorged block is finalized

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 8 comments.

File	Description
pkg/logpoller/log_poller.go	Core implementation changes: added isReplay parameter, extracted headerByNumber and handleReorg methods, enhanced reorg detection logic for replay scenarios
pkg/logpoller/log_poller_test.go	Updated all test calls to include isReplay=false parameter, added comprehensive TestLogPoller_Reorg_On_Replay test with three test cases
pkg/logpoller/log_poller_internal_test.go	Updated all test calls to include isReplay=false parameter
pkg/logpoller/helper_test.go	Updated PollAndSaveLogs wrapper to pass isReplay=false

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[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 4 comments.

---

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[Copilot]

Inconsistent context usage: This line uses testutils.Context(t) while the rest of the test function uses t.Context() (lines 2248, 2251, 2254). For consistency and to ensure the context is properly tied to the test lifecycle, consider using t.Context() here as well.

Suggested change

	dbBlock, err := th.ORM.SelectBlockByNumber(testutils.Context(t), reorgedBlock.Number().Int64())
	dbBlock, err := th.ORM.SelectBlockByNumber(t.Context(), reorgedBlock.Number().Int64())

[Copilot]

Misleading comment: The comment says "bury it under 1 new block" but the actual number of blocks added after the reorg depends on tc.numberOfBlocksAfterReorg, which varies per test case (0, 1, or 5). Consider updating the comment to accurately reflect this, such as "Replace block 11 with a new block and optionally add additional blocks on top of it".

Suggested change

	// Replace block 11 with a new block and bury it under 1 new block
	// Replace the reorged block with a new block and add a variable number of blocks on top

[Copilot]

Misleading error message: The error message says "failed to get latest finalized block from db" but the function actually calls orm.SelectLatestBlock (line 1063), not SelectLatestFinalizedBlock. The error message should be updated to "failed to get latest block from db" for accuracy.

Suggested change

	return nil, pkgerrors.Wrap(err, "failed to get latest finalized block from db")
	return nil, pkgerrors.Wrap(err, "failed to get latest block from db")

[Copilot]

Missing parameter documentation: The function comment should document the new isReplay parameter, explaining that it should be true when called during a replay operation and false during normal polling. This helps future maintainers understand when to use each value.

Suggested change

	// conditions this would be equal to lastProcessed.BlockNumber + 1.
	// conditions this would be equal to lastProcessed.BlockNumber + 1. The isReplay flag should be
	// true when PollAndSaveLogs is called as part of a replay operation and false during normal polling.