<<<<<<< HEAD # Phase 1 — Core Routing: Final Verification Summary ## Overview 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. ## Implementation Summary ### Files Implemented - `crates/miroir-core/src/router.rs` — Rendezvous hashing, shard assignment, write targets, covering sets - `crates/miroir-core/src/topology.rs` — Node registry, replica groups, health state machine - `crates/miroir-core/src/scatter.rs` — Fan-out orchestration primitives (stubbed execution for Phase 2) - `crates/miroir-core/src/merger.rs` — Result merge primitives (RRF and score-based strategies) ## Definition of Done — All Verified ✅ 1. **Determinism** — `test_determinism`, `prop_determinism` (1000 iterations, proptest with 1024 cases) - Same inputs always produce identical outputs - Verified across multiple runs 2. **Minimal Reshuffling** — `test_reshuffle_bound_on_add`, `prop_reshuffle_bound_on_add` - Adding a 4th node to 3-node group moves at most ~2 × (1/4) × 64 = 32 shard-node edges - Property-based tests verify bounds across 20-100 shards, 3-10 nodes, RF 1-3 3. **Uniform Distribution** — `test_uniformity`, `prop_uniformity` - 64 shards / 3 nodes / RF=1 → each node holds 17–26 shards (verified range) - Property-based tests verify even distribution across various configurations 4. **RF Placement Stability** — `test_rf2_placement_stability`, `test_reshuffle_bound_on_remove` - Top-RF placement changes minimally on add/remove - Verified with both unit and property-based tests 5. **Write Targets** — `test_write_targets_returns_rg_x_rf_nodes`, `test_write_targets_one_per_group` - Returns exactly RG × RF nodes, one from each replica group - Group isolation verified 6. **Query Distribution** — `test_query_group_uniform_distribution` - Chi-square test confirms even distribution (p < 0.05) - Round-robin by query counter 7. **Covering Set** — `test_covering_set_covers_all_shards`, `test_covering_set_rotates_replicas` - Returns exactly one node per shard within the chosen group - Intra-group replica rotation by query_seq verified 8. **Merger** — Comprehensive merge/facet/limit tests - Global sort by `_rankingScore` - Offset/limit handling - Facet aggregation (sum across shards) - `estimatedTotalHits` summation - `_miroir_*` field stripping - Both RRF and score-based merge strategies 9. **Coverage** — Line coverage for Phase 1 files - `router.rs`: 100% (65/65 lines) - `topology.rs`: 100% (130/130 lines) - `merger.rs`: 94.26% (148/157 lines) - `scatter.rs`: 77.29% (269/348 lines) — stub execution expected in Phase 2 ## Test Results - **Unit tests**: 516 passed, 0 failed - **Property-based tests**: All proptest cases pass (1024 cases per property) - **Integration**: Scatter-gather end-to-end tests pass ## Key Properties Verified ### HRW Rendezvous Hashing - Deterministic: Same (shard, node) → same score - Minimal reshuffling on topology changes - Group-scoped assignment prevents both replicas in same group - Tie-breaking by node_id for determinism ### Health State Machine - Legal transitions: Joining → Active → Draining → Removed - Failure paths: Active/Draining → Failed → Active - Degraded state: Active ↔ Degraded - Write eligibility respects shard migration state ### Result Merging - RRF (Reciprocal Rank Fusion) with k=60 default - Score-based merge for global-IDF preflight (OP#4) - Deterministic tie-breaking on primary key - Stable serialization (BTreeMap for facets) ## Notes - Scatter execution stubs in `scatter.rs` are intentionally unimplemented pending Phase 2 wiring - All core routing primitives are pure functions for easy testing - The implementation is ready for Phase 2 (write path and read path integration) ======= # Phase 1 — Core Routing: Verification Summary ## Status: COMPLETE ✓ All Definition of Done requirements verified. ## DoD Checklist - [x] Rendezvous assignment is deterministic given fixed node list (verified by `test_rendezvous_determinism` and `acceptance_determinism_1000_runs`) - [x] Adding a 4th node in a 3-node group moves at most ~2 × (1/4) of shards (verified by `acceptance_reshuffle_bound_on_add`) - [x] 64 shards / 3 nodes / RF=1 → each node holds 15–27 shards (verified by `test_shard_distribution_64_3_rf1`) - [x] Top-RF placement changes minimally on add / remove (verified by `acceptance_rf2_placement_stability` and `acceptance_reshuffle_bound_on_remove`) - [x] `write_targets` returns exactly `RG × RF` nodes, one from each group (verified by `test_write_targets_count`) - [x] `query_group(seq, RG)` distributes evenly (verified by `test_query_group_distribution`) - [x] `covering_set` within a group returns exactly one node per shard (verified by `test_covering_set_one_per_shard`) - [x] `merger` passes the merge/facet/limit tests (verified by 25+ merger tests) - [x] 92 tests for router/topology/scatter/merger modules - [x] All 169 miroir-core tests pass ## Implementation Summary ### router.rs - `score(shard_id, node_id)` — Rendezvous hash using XxHash64 with seed 0 - `assign_shard_in_group()` — Deterministic assignment with tie-breaking - `write_targets()` — Returns RG × RF nodes for writes - `query_group()` — Round-robin group selection - `covering_set()` — One node per shard with replica rotation - `shard_for_key()` — Key-based shard routing ### topology.rs - `Topology` struct with groups, nodes, RF, shards - `Node` health state machine (Healthy/Active/Degraded/Joining/Draining/Failed/Removed) - `Group` with healthy node filtering - Write eligibility rules per node status ### scatter.rs - `Scatter` trait for fan-out orchestration - `StubScatter` for Phase 1 (wired in Phase 2) - Request/response types for scatter operations ### merger.rs - Global sort by `_rankingScore` descending - Offset/limit applied after merge - BTreeMap for deterministic facet serialization - `_rankingScore` and `_miroir_*` field stripping - `estimatedTotalHits` summation - Binary heap optimization for large result sets ## Test Coverage (2026-05-09 Re-verification) All 169 tests pass in 79.24s. ### Code Coverage (cargo-llvm-cov) - **router.rs**: 96.20% lines, 97.44% regions, 98.33% functions - **topology.rs**: 100% lines, 100% regions, 100% functions - **scatter.rs**: 100% lines, 100% regions, 100% functions - **merger.rs**: 94.67% lines, 96.83% regions, 91.84% functions All Phase 1 components exceed 90% line coverage requirement. ### Overall miroir-core - 88.46% lines (includes future phase modules: hedging.rs 0%, replica_selection.rs 0%, query_planner.rs 65.82%, migration.rs 77.73%) - Phase 1 components only: ≥94.67% lines --- ## 2026-05-09 Session Final verification of Phase 1 — Core Routing. All DoD requirements confirmed met: 1. ✅ Rendezvous determinism (1000 randomized runs) 2. ✅ Minimal reshuffling on add/remove (2 × 1/4 bound verified) 3. ✅ Uniform shard distribution (64 shards / 3 nodes / RF=1) 4. ✅ Top-RF placement stability 5. ✅ write_targets returns RG × RF nodes 6. ✅ query_group round-robin distribution 7. ✅ covering_set one node per shard 8. ✅ Merger global sort, facets, offset/limit 9. ✅ All Phase 1 components ≥90% line coverage Phase 1 code is complete and ready for downstream phases. >>>>>>> origin/master