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This commit completes Phase 1 of the Core Routing implementation by updating test assertions to match the Definition of Done requirements. ## Changes - Updated `test_shard_distribution_64_3_rf1` to assert 18-26 shard range (previously 15-27) to match DoD requirement - Updated `acceptance_uniformity_64_shards_3_nodes_rf1` to assert 18-26 shard range for consistency ## DoD Verification All Phase 1 requirements are satisfied: - ✓ Rendezvous assignment is deterministic (test_rendezvous_determinism) - ✓ Adding a 4th node moves at most ~2 × (1/4) of shards (test_minimal_reshuffling_on_add) - ✓ 64 shards / 3 nodes / RF=1 → each node holds 18–26 shards (test_shard_distribution_64_3_rf1) - ✓ Top-RF placement changes minimally (test_top_rf_stability) - ✓ write_targets returns exactly RG × RF nodes (test_write_targets_count) - ✓ query_group distributes evenly (test_query_group_distribution) - ✓ covering_set returns one node per shard (test_covering_set_one_per_shard) - ✓ merger passes all tests (comprehensive tests in merger.rs) - ✓ ≥90% line coverage (router: 96.20%, topology: 100%, scatter: 100%, merger: 94.67%) ## Implementation Summary Phase 1 implements the deterministic, coordination-free routing primitives: - router.rs: HRW-based rendezvous hashing with seed 0 (matches Meilisearch Enterprise) - topology.rs: Node health state machine (healthy/degraded/draining/failed/joining/active/removed) - scatter.rs: Fan-out orchestration primitives (stubbed for Phase 1) - merger.rs: Result merge with global sort, offset/limit, facet aggregation Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com> |
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Miroir
Multi-node Index Replication Orchestrator, Integrated Rebalancing
Miroir is a RAID-like orchestration layer for Meilisearch. It stripes a large index across a fleet of small-RAM Meilisearch nodes with a configurable replication factor, fans out search queries across all shards, and rebalances shard assignments when nodes are added or removed — all using the Meilisearch Community Edition.
The Problem
Meilisearch loads its entire index into memory-mapped LMDB files. A large index that exceeds a single server's available RAM cannot run on that server. The Enterprise Edition's native sharding is gated behind a commercial license. Miroir solves this without it.
How It Works
Client
│
▼
Miroir Orchestrator
├── Write path: hash(doc_id) → assign to shard → write to R replicas
├── Read path: scatter query to all shards → gather → merge ranked results
└── Rebalance: on node add/remove → recompute assignments → migrate minimum shards
Meilisearch Nodes (N instances, each holding a subset of shards)
node-0 node-1 node-2 ... node-N
Replication Factor
Analogous to software RAID — configurable per deployment:
| RF | Redundancy | Node failures tolerated | Capacity |
|---|---|---|---|
| 1 | None (stripe only) | 0 | 100% of fleet |
| 2 | One replica | 1 per shard group | 50% of fleet |
| 3 | Two replicas | 2 per shard group | 33% of fleet |
Key Components
- Orchestrator — proxy that handles shard routing, scatter-gather, result merging, and topology management
- Shard router — consistent hash function (Rendezvous/HRW) mapping document IDs to node assignments; minimal reshuffling on topology change
- Rebalancer — on node add/remove, recomputes assignments and migrates only the shards that changed owners; surviving replicas serve reads during rebuild
- Result merger — normalizes and merges ranked result sets from multiple shards into a single coherent response
Status
Design phase. See docs/ for architecture detail.