Fix/pr71 coderabbit issues

[wcatz]

Summary by CodeRabbit

• Bug Fixes
  • Enhanced leader schedule validation by verifying epoch nonce consistency before using cached schedules.
  • Automatically detects and refreshes stale schedules instead of relying on potentially outdated data.
  • Strengthens reliability of leaderlog queries and nextblock operations by preventing use of schedules with mismatched nonces.
  • Ensures on-demand schedule computations align with expected epoch nonce values for improved accuracy.

[coderabbitai]

Caution

Review failed

The pull request is closed.

📝 Walkthrough

Walkthrough

This PR adds verified epoch nonce caching to NonceTracker and integrates nonce validation checks throughout the leader schedule pipeline. Cached schedules are now validated against the currently expected nonce before use; mismatches trigger fresh schedule computation instead of relying on stale data.

Changes

Cohort / File(s)	Summary
Nonce Verification and Caching nonce.go	Introduces in-memory cache verifiedNonces in NonceTracker and adds GetVerifiedNonceForEpoch() method. In full mode, checks cache first, recomputes via ComputeEpochNonce if needed, repairs DB cache on mismatch, and updates both caches. Delegates to GetNonceForEpoch in lite mode.
Schedule Validation commands.go	Adds scheduleNonceMatches() helper method to Indexer to verify that a cached LeaderSchedule was built with the expected epoch nonce. Replaces direct nonce fetches with GetVerifiedNonceForEpoch calls in leaderlog and nextblock paths.
Validation Integration main.go	Integrates scheduleNonceMatches() checks in leaderlog trigger and backfill paths to validate cached schedules before use. Replaces GetNonceForEpoch with GetVerifiedNonceForEpoch for verified nonce retrieval. Adds validation guard before caching schedule existence flags.

Sequence Diagram

sequenceDiagram
    actor Client
    participant Indexer
    participant NonceTracker
    participant Database
    
    Client->>Indexer: Request leaderlog/nextblock
    Indexer->>Indexer: Check cached schedule
    alt Cached schedule exists
        Indexer->>NonceTracker: GetVerifiedNonceForEpoch(epoch-1)
        NonceTracker->>NonceTracker: Check verifiedNonces cache
        alt Nonce in cache
            NonceTracker-->>Indexer: Return cached nonce
        else Cache miss
            NonceTracker->>NonceTracker: ComputeEpochNonce()
            NonceTracker->>Database: Check DB cache
            alt DB differs from computed
                NonceTracker->>Database: Write corrected nonce
            end
            NonceTracker->>NonceTracker: Update verifiedNonces cache
            NonceTracker-->>Indexer: Return verified nonce
        end
        Indexer->>Indexer: scheduleNonceMatches(cached_schedule)
        alt Nonces match
            Indexer-->>Client: Use cached schedule
        else Nonces mismatch (stale)
            Indexer->>Indexer: Compute fresh schedule
            Indexer-->>Client: Use fresh schedule
        end
    else No cached schedule
        Indexer->>Indexer: Compute fresh schedule
        Indexer-->>Client: Return schedule
    end

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Estimated Code Review Effort

🎯 4 (Complex) | ⏱️ ~50 minutes

Possibly Related PRs

• fix(nonce): era-aware stability window and Babbage VRF domain separator #57: Introduces era-aware changes to nonce computation and stability-window logic in nonce.go that directly impact the behavior of ComputeEpochNonce called by the new GetVerifiedNonceForEpoch method.
• fix(nonce): use prevHash-based labNonce with epoch lag #58: Modifies epoch nonce handling and nonce value derivation logic (labNonce/prevHash lag, vrfNonceValueForEpoch) that directly affects the nonce verification and caching mechanisms introduced here.
• fix(nonce): update wrong nonces during backfill instead of skipping #70: Modifies nonce backfill and repair logic in nonce.go to detect and correct mismatched epoch nonces, which aligns with the DB cache repair behavior added in GetVerifiedNonceForEpoch.

Poem

🐰 A rabbit hops through schedules old and new,
Checking nonces verify before they're due,
Stale caches caught, fresh schedules bloom,
With verification logic clearing the gloom! ✨

✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch fix/pr71-coderabbit-issues

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