fix(nonce): recompute evolving nonce on block count mismatch

[wcatz]

Summary

• ResyncFromDB now cross-checks epoch_nonces.block_count against actual COUNT(*) FROM blocks
• On mismatch (OOM between CopyFrom and ProcessBatch), recomputes evolving nonce inline from raw VRF outputs
• Prevents stale nonce from corrupting the nonce chain for all subsequent epochs

Root cause

InsertBlockBatch (CopyFrom) writes blocks atomically, but ProcessBatch (nonce evolution) runs after as a separate step. An OOM between the two leaves blocks in the DB but epoch_nonces.block_count stale. On restart, ResyncFromDB read the stale count uncorrected.

Test plan

• TestResyncFromDB_BlockCountMismatch — simulates OOM scenario, verifies recompute
• All 70 tests pass

Summary by CodeRabbit

• Bug Fixes

  • Fixed nonce synchronization to detect and correct block count mismatches, ensuring accurate nonce recomputation during data recovery scenarios.

• Tests

  • Added test coverage for block count mismatch detection and recovery.

[coderabbitai]

Caution

Review failed

The pull request is closed.

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 3860134b-77e3-4d93-b2a2-6be162997dcf

📥 Commits

Reviewing files that changed from the base of the PR and between 8710e09 and 3fef027.

📒 Files selected for processing (2)

• comprehensive_test.go
• nonce.go

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📝 Walkthrough

Walkthrough

This pull request adds detection and recovery logic for block count mismatches in the nonce synchronization process. When a mismatch occurs between stored block count and actual blocks in the database, the evolving nonce is recomputed from raw VRF outputs and state is repaired.

Changes

Cohort / File(s)	Summary
Nonce Recovery Logic nonce.go	Adds cross-check in ResyncFromDB to detect block_count mismatches; when detected, recomputes evolving nonce from raw VRF outputs by seeding from previous epoch nonce, fetching VRF outputs, iterating evolution, and persisting corrected nonce and block_count.
Test Coverage comprehensive_test.go	Adds TestResyncFromDB_BlockCountMismatch test that verifies mismatch detection, nonce recomputation, and block_count repair. Introduces bytes import for nonce value comparison.

Sequence Diagram

sequenceDiagram
    participant NT as NonceTracker
    participant DB as Database
    participant VO as VRF Outputs
    
    NT->>DB: ResyncFromDB (post-bulk insert)
    DB->>DB: Count blocks for epoch
    DB->>NT: Return actual block count
    NT->>NT: Compare stored vs actual block_count
    
    alt Block count mismatch detected
        NT->>DB: Fetch previous epoch evolving nonce
        DB->>NT: Return previous nonce (or initial)
        NT->>VO: GetVrfOutputsForEpoch(current epoch)
        VO->>NT: Return VRF outputs list
        NT->>NT: Iterate VRF outputs to evolve nonce
        NT->>DB: Upsert recomputed nonce + correct block_count
        DB->>NT: Persist complete
        NT->>NT: Update evolvingNonce & blockCount in-memory
        NT->>NT: Log recomputation event
    else Block count matches
        NT->>NT: No action (nonce is valid)
    end

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Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~22 minutes

Possibly related PRs

• fix(nonce): correct epoch nonce indexing — revert v2.7.9 off-by-one #78: Directly related — both add block_count mismatch detection and nonce recomputation logic with corresponding tests in ResyncFromDB.
• fix(nonce): correct TICKN candidate freeze and η_ph hash #88: Related — both extend nonce recomputation in nonce.go to recover epoch nonces using GetVrfOutputsForEpoch and raw VRF outputs.
• fix(integrity): startup DB integrity check for HA failover #77: Related — both implement the same remediation: detecting block_count/nonce divergence and repairing evolving nonce from stored VRF outputs.

Poem

🐰 A mismatch in blocks? Oh, what a plight!
But our nonce recovery sets things right—
We fetch the VRF seeds from the store,
Evolve and repair, block counts restore!
Through epochs we hop with nonce held tight 🌱

✨ Finishing Touches

• 📝 Generate docstrings (stacked PR)
• 📝 Generate docstrings (commit on current branch)

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch fix/resync-block-count-mismatch

📝 Coding Plan

• Generate coding plan for human review comments

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