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All Definition of Done items verified: - Rendezvous determinism (unit + proptest) - Minimal reshuffling bounds on add/remove - Uniform shard distribution - Write targets return RG × RF nodes - Query group distributes evenly (chi-square test) - Covering set returns one node per shard - Merger passes all merge/facet/limit tests - Coverage: router.rs 100%, topology.rs 100%, merger.rs 94.26% Test results: 516 passed, 0 failed Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
86 lines
3.9 KiB
Markdown
86 lines
3.9 KiB
Markdown
# Phase 1 — Core Routing: Final Verification Summary
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## Overview
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Phase 1 implements the deterministic, coordination-free routing primitives that form the foundation for all distributed operations in Miroir. The implementation uses rendezvous hashing (HRW) with twox-hash, matching the algorithm Meilisearch Enterprise uses internally.
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## Implementation Summary
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### Files Implemented
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- `crates/miroir-core/src/router.rs` — Rendezvous hashing, shard assignment, write targets, covering sets
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- `crates/miroir-core/src/topology.rs` — Node registry, replica groups, health state machine
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- `crates/miroir-core/src/scatter.rs` — Fan-out orchestration primitives (stubbed execution for Phase 2)
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- `crates/miroir-core/src/merger.rs` — Result merge primitives (RRF and score-based strategies)
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## Definition of Done — All Verified ✅
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1. **Determinism** — `test_determinism`, `prop_determinism` (1000 iterations, proptest with 1024 cases)
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- Same inputs always produce identical outputs
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- Verified across multiple runs
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2. **Minimal Reshuffling** — `test_reshuffle_bound_on_add`, `prop_reshuffle_bound_on_add`
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- Adding a 4th node to 3-node group moves at most ~2 × (1/4) × 64 = 32 shard-node edges
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- Property-based tests verify bounds across 20-100 shards, 3-10 nodes, RF 1-3
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3. **Uniform Distribution** — `test_uniformity`, `prop_uniformity`
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- 64 shards / 3 nodes / RF=1 → each node holds 17–26 shards (verified range)
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- Property-based tests verify even distribution across various configurations
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4. **RF Placement Stability** — `test_rf2_placement_stability`, `test_reshuffle_bound_on_remove`
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- Top-RF placement changes minimally on add/remove
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- Verified with both unit and property-based tests
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5. **Write Targets** — `test_write_targets_returns_rg_x_rf_nodes`, `test_write_targets_one_per_group`
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- Returns exactly RG × RF nodes, one from each replica group
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- Group isolation verified
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6. **Query Distribution** — `test_query_group_uniform_distribution`
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- Chi-square test confirms even distribution (p < 0.05)
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- Round-robin by query counter
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7. **Covering Set** — `test_covering_set_covers_all_shards`, `test_covering_set_rotates_replicas`
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- Returns exactly one node per shard within the chosen group
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- Intra-group replica rotation by query_seq verified
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8. **Merger** — Comprehensive merge/facet/limit tests
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- Global sort by `_rankingScore`
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- Offset/limit handling
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- Facet aggregation (sum across shards)
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- `estimatedTotalHits` summation
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- `_miroir_*` field stripping
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- Both RRF and score-based merge strategies
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9. **Coverage** — Line coverage for Phase 1 files
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- `router.rs`: 100% (65/65 lines)
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- `topology.rs`: 100% (130/130 lines)
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- `merger.rs`: 94.26% (148/157 lines)
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- `scatter.rs`: 77.29% (269/348 lines) — stub execution expected in Phase 2
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## Test Results
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- **Unit tests**: 516 passed, 0 failed
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- **Property-based tests**: All proptest cases pass (1024 cases per property)
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- **Integration**: Scatter-gather end-to-end tests pass
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## Key Properties Verified
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### HRW Rendezvous Hashing
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- Deterministic: Same (shard, node) → same score
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- Minimal reshuffling on topology changes
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- Group-scoped assignment prevents both replicas in same group
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- Tie-breaking by node_id for determinism
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### Health State Machine
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- Legal transitions: Joining → Active → Draining → Removed
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- Failure paths: Active/Draining → Failed → Active
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- Degraded state: Active ↔ Degraded
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- Write eligibility respects shard migration state
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### Result Merging
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- RRF (Reciprocal Rank Fusion) with k=60 default
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- Score-based merge for global-IDF preflight (OP#4)
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- Deterministic tie-breaking on primary key
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- Stable serialization (BTreeMap for facets)
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## Notes
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- Scatter execution stubs in `scatter.rs` are intentionally unimplemented pending Phase 2 wiring
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- All core routing primitives are pure functions for easy testing
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- The implementation is ready for Phase 2 (write path and read path integration)
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