No description
690cefe04e
Implement plan §2 "Adding a node to an existing group":
1. Admin API endpoints now use Rebalancer methods:
- POST /_miroir/nodes → Rebalancer.add_node()
- POST /_miroir/nodes/{id}/drain → Rebalancer.drain_node()
- DELETE /_miroir/nodes/{id} → Rebalancer.remove_node()
2. Node addition flow:
- Mark node as `joining`
- Recompute assignments → affected_shards where new node enters top-RF
- Dual-write: writes go to both old owner and new node
- Background migration via _miroir_shard filter (paginated)
- Mark `active`; stop dual-write
- Delete migrated shard from old node
3. Integration tests (p42_node_addition.rs):
- 3→4 node migration with 10K docs
- Chaos: writes during migration caught by dual-write
- Performance: ≤ total_docs/(Ng+1) × 1.1 docs moved
- Log inspection: old node not queried after migration
- Pagination verification with limit/offset
- Dual-write verification
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.