refactor: metadata service

[petarjuki7]

Issue Addressed

Addresses Issue #807

Proposed Changes

• Split MetadataService into two focused modules
• DutyInputPublisher handles timing and publishing of duty inputs
• AggregatorConsensusBuilder handles beacon fetches and consensus data construction

Additional Info

[claude-code-actions-sigp]

Claude finished @petarjuki7's task in 1m 15s —— View job

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Code Review Complete

I've reviewed this refactoring PR that splits MetadataService into two focused modules. The refactoring follows solid separation of concerns principles and is well-executed overall, with some recommendations for improvement.

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Architecture & Design ✅

Strengths:

• Clear separation between timing/publishing (DutyInputPublisher) and data fetching/building (AggregatorConsensusBuilder)
• The AggregatorConsensusBuilder is now a pure builder pattern with no side effects, making it easier to test
• Good single-responsibility adherence - each module has a well-defined purpose
• Backwards compatibility preserved with deprecated re-export

Observations:

• The refactoring aligns well with CLAUDE.md principles on modular boundaries and questioning intermediaries
• The new structure makes the timing phases (slot start, 1/3 slot, 2/3 slot) explicit and clear

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Code Quality ✅

Strengths:

• Comprehensive documentation with module-level and function-level comments
• Clear separation of pure helper functions from stateful operations in aggregator_consensus_builder.rs:560-611
• Good use of Rust idioms (iterator chains, Result propagation with ?)
• Proper error handling throughout

Issues Identified:

1. Inconsistent terminology in comments (anchor/validator_store/src/lib.rs:521, 562)

   • Comments still refer to "MetadataService" but should reference "DutyInputPublisher"

   // Line 521: "Update validator voting assignments (called by `MetadataService` at slot start)."
   // Line 562: "Update aggregator voting assignments (called by `MetadataService` Phase 3 at 2/3 slot)."

   Should be updated to reference DutyInputPublisher for consistency.

2. Deprecated module could have clearer migration path (anchor/validator_store/src/lib.rs:6-13)

   • The deprecation notice is helpful, but could benefit from a since version that matches your actual release versioning
   • Consider if since = "0.1.0" is accurate or should reflect the actual version where this will be released

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Security ✅

No security concerns identified:

• No changes to cryptographic operations or key handling
• Error handling preserves security context without exposing sensitive data
• Slashing protection logic unchanged

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Performance 👍

Strengths:

• Smart use of FuturesUnordered for parallel beacon node fetches with timeout (lines 336-383, 466-485 in aggregator_consensus_builder.rs)
• Single-pass data transformation minimizes iterations (lines 316-405 in duty_input_publisher.rs)
• LRU cache for decrypted keys remains intact
• Proper timeout handling prevents blocking on slow beacon nodes

Observation:

• The BEACON_API_FETCH_TIMEOUT of 2 seconds (line 48 in duty_input_publisher.rs) is well-justified given SSV's additional QBFT and P2P latency requirements

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Testing 🟡

Strengths:

• Excellent test coverage in aggregator_consensus_builder.rs (lines 613-1512)
• Tests are well-structured with clear P0/P1/P2 priority categories
• Tests verify wire compatibility, deterministic output, and validator compatibility
• Good use of helper functions to create test data
• Edge cases covered (empty inputs, partial failures, etc.)

Gap Identified:

• No tests for DutyInputPublisher timing logic or the three phases
• The spawned async tasks in start_update_service (lines 109-186 in duty_input_publisher.rs) are not unit tested
• Integration tests would be valuable to verify the coordination between phases

Recommendation:
Consider adding tests for:

• Phase timing correctness (slot start, 1/3 slot, 2/3 slot)
• Watch channel updates and subscriber behavior
• Error recovery in each phase

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Documentation ✅

Strengths:

• Excellent module-level documentation explaining separation of concerns
• Clear inline comments explaining CRITICAL requirements for consensus compatibility
• Good use of visual separators (═══) to delineate sections
• Helpful comments about timing and coordination

Minor Issue:

• File rename from metadata_service.rs to aggregator_consensus_builder.rs is documented in the module header, but the PR description could be more detailed about what specifically was extracted vs what remained

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Specific Code Issues

Minor: Unused import warning potential

In aggregator_consensus_builder.rs:36, Instrument trait is imported but only used once. This is fine but worth noting for future optimization.

Positive: Metric instrumentation

Good addition of metrics for tracking fetch success/failure rates and partial results (lines 433-442, 541-554 in aggregator_consensus_builder.rs).

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Recommendations

1. Update stale comments - Fix references to MetadataService in lib.rs (lines 521, 562)

2. Consider adding DutyInputPublisher tests - The timing logic and phase coordination would benefit from unit/integration tests

3. Verify deprecation version - Ensure since = "0.1.0" matches your actual versioning scheme

4. Consider extracting test helpers - The test helper functions (lines 636-713 in aggregator_consensus_builder.rs) are well-written and could potentially be shared if other modules need similar test data

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Summary

This is a well-executed refactoring that improves code organization and maintainability. The separation of concerns is clear, and the implementation quality is high. The main areas for improvement are:

• Updating stale documentation references
• Adding tests for the timing/publishing logic
• Minor cleanup of deprecated module metadata

The consensus-critical sorting and filtering logic is well-tested and properly documented. No blocking issues identified.

Recommendation: Approve with minor comments addressed

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[diegomrsantos]

Please let's go back to small PRs that are easy to review

[petarjuki7]

Please let's go back to small PRs that are easy to review

Sure, I think I messed something up with git, it should have been a smaller change, will fix then put as ready for review

[petarjuki7]

Please let's go back to small PRs that are easy to review

Ah okay, the problem is that before the latest commit, git registered metadata_service.rs → aggregator_consensus_builder.rs as a rename, so the diff wasn't so big. With the latest changes it's showing now as "deleted old file and add new file".
The 99% (1878 lines) of deletions is just the metadata_service being deleted, and the additions are refactors.
There aren't any logic changes, just refactoring. Hopefully that makes it easier to review.

[diegomrsantos]

Please let's go back to small PRs that are easy to review

Ah okay, the problem is that before the latest commit, git registered metadata_service.rs → aggregator_consensus_builder.rs as a rename, so the diff wasn't so big. With the latest changes it's showing now as "deleted old file and add new file". The 99% (1878 lines) of deletions is just the metadata_service being deleted, and the additions are refactors. There aren't any logic changes, just refactoring. Hopefully that makes it easier to review.

I'd still find a way not to mark it as a new file (if that's the issue) or split it into smaller PRs. There are several studies showing that big PRs cause many issues and are hard to review, and slow to merge.

[shane-moore]

nit: could simplify further by having the builder own the full pipeline:

  async fn publish_aggregation_assignments(&self) -> Result<(), String> {
      let slot = self.slot_clock.now().ok_or("Failed to read slot clock")?;
      let attesters = self.duties_service.attesters(slot);
      let sync_duties =
  self.duties_service.sync_duties.get_duties_for_slot::<E>(slot, &self.spec);

      let aggregation_assignments = build_aggregation_assignments(
          slot,
          &attesters,
          sync_duties.as_ref().map(|d| &d.aggregators),
          &self.validator_store,
          &self.beacon_nodes,
          &self.spec,
          &self.fork_schedule,
          BEACON_API_FETCH_TIMEOUT,
      )
      .await?;

      self.validator_store
          .update_aggregation_assignments(aggregation_assignments);

      trace!(%slot, "Published AggregationAssignments");
      Ok(())
  }

build_aggregation_assignments does the grouping, fork check, voting context
fetch, beacon fetches, and returns a complete AggregationAssignments. This
eliminates GroupedDuties (becomes local variables inside the builder), and
SyncAggregatorData, SyncByCommitteeMap, SyncAggregatorsBySubnet all become
private to the builder module