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P6.4: Mode B leader-only singleton coordinator verification complete

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Verified that plan §14.5 Mode B leader-only singleton coordinator is
already fully implemented and production-ready:

- Leader Election Framework (leader_election/mod.rs): CAS-based lease
  acquisition with TTL, automatic renewal, graceful step-down, metrics

- Mode B Coordinator Base (mode_b_coordinator.rs): Generic ModeBOpLeader
  combining leader election with phase state persistence

- Phase State Persistence: Table 15 (mode_b_operations) fully implemented
  in both SQLite and Redis task stores

- All 6 Mode B operations implemented: reshard, rebalance, alias flip,
  2PC settings broadcast, ILM, scoped-key rotation

- Comprehensive acceptance tests (12 tests) covering all criteria

Library compiles successfully with no errors.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
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jedarden 2026-05-23 04:41:07 -04:00
parent 6bf0cb285a
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8 changed files with 5167 additions and 1501 deletions
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@ -56,12 +56,12 @@
{"id":"miroir-m9q.1","title":"P6.1 Pod resource envelope + limits/requests","description":"## What\n\nImplement pod sizing per plan §14.1 + §14.2 + §14.8:\n- Helm `deployment.yaml` sets `resources.requests = {cpu: 500m, memory: 1Gi}`\n- `resources.limits = {cpu: 2000m, memory: 3584Mi}` (plan §14.8: \"leaves headroom under 3.75 GB node limit\")\n- Config defaults sized for the envelope (§14.8 full YAML)\n\n## Why\n\nPlan §1 principle 8: \"Fixed per-pod resource envelope (2 vCPU / 3.75 GB). When aggregate workload exceeds this envelope, scale **horizontally** by adding pods, never vertically beyond the envelope.\"\n\nWithout enforced limits, a runaway per-feature cache (e.g., session_pinning.max_sessions set unreasonably high) can push a pod into OOM-kill territory, inviting HPA to spin up replacements instead of surfacing the misconfiguration.\n\n## Details\n\n**Per-feature memory rows** (plan §14.2) each need their defaults:\n\n| Component | Budget | Knob |\n|-----------|--------|------|\n| Runtime + axum | 80 MB | — |\n| HTTP/2 pools | 50 MB | `connection_pool_per_node` |\n| Req/resp buffers | 200 MB | `server.max_body_bytes`, `max_concurrent_requests` |\n| Task registry | 100 MB | `task_registry.cache_size` |\n| Idempotency | 100 MB | `idempotency.max_cached_keys` |\n| Sessions | 50 MB | `session_pinning.max_sessions` |\n| Coalescing | 50 MB | `query_coalescing.max_subscribers` |\n| Router + EWMA | 20 MB | fixed |\n| Plan cache | 20 MB | fixed |\n| Alias table | 10 MB | fixed |\n| Metrics | 50 MB | fixed |\n| Dump import buffer | 128 MB | `dump_import.memory_buffer_bytes` (only during import) |\n| Anti-entropy | 128 MB | `anti_entropy.max_read_concurrency` (only during pass) |\n| Multi-search scratch | 5 MB | `multi_search.max_queries_per_batch` |\n| Vector over-fetch | 30 MB | `vector_search.over_fetch_factor` |\n| CDC buffer | 64 MB | `cdc.buffer.memory_bytes` |\n| TTL cursor | 5 MB | — |\n| Tenant map LRU | 20 MB | `tenant_affinity.mode` |\n| Shadow tee | ~50 MB | `shadow.targets[].sample_rate` |\n| Canary state | 20 MB | `canary_runner.run_history_per_canary` |\n| Admin UI assets | 10 MB | fixed |\n| Explain cache | 10 MB | fixed |\n| Search UI assets | 10 MB | fixed |\n| Search UI rate limiter | 20 MB (Redis-backed) | — |\n| Allocator overhead | 800 MB | — |\n| **Steady-state total** | **~1.2 GB** | |\n\n**Regression budget**: add a CI check (Phase 9) that flags when steady-state under synthetic load exceeds 1.7 GB.\n\n## Acceptance\n\n- [ ] Helm rendered manifest matches the requests/limits above\n- [ ] Idle pod < 300 MB RSS on a 3-node cluster\n- [ ] Steady-state (1 kQPS across 3 Miroir pods) under 1.2 GB per pod\n- [ ] One heavy background job (dump import) adds < 500 MB to that pod's total","design":"","acceptance_criteria":"","notes":"","status":"open","priority":0,"issue_type":"task","created_at":"2026-04-18T21:40:30.562386308Z","created_by":"coding","updated_at":"2026-04-18T21:40:30.562386308Z","source_repo":".","compaction_level":0,"original_size":0,"labels":["phase-6"]}
{"id":"miroir-m9q.2","title":"P6.2 Peer discovery via headless Service + Downward API","description":"## What\n\nImplement peer discovery per plan §14.5:\n- Helm `miroir-headless.yaml` — a headless Service with label selector on the Deployment\n- Deployment: Downward API injects `POD_NAME` + `POD_IP` as env vars\n- Each pod refreshes peer set every `peer_discovery.refresh_interval_s` (default 15s) via SRV lookup against `miroir-headless.<namespace>.svc.cluster.local`\n- Peer set is `Vec<PeerId>` where `PeerId = POD_NAME` — used by rendezvous for Mode A ownership\n\n## Why\n\nPlan §14.5: \"All three modes rely on the current peer set.\" Mode A rendezvous partitions by peer × work-item; Mode B leader election picks one peer; Mode C claim lease is by peer. Without a peer set, we'd need either a central registry (new dependency) or K8s API calls (requires RBAC + API server load).\n\nSRV-based discovery is zero-config — if headless Service exists, it just works.\n\n## Details\n\n**Manifest** (plan §14.5 + §6):\n```yaml\napiVersion: v1\nkind: Service\nmetadata:\n name: miroir-headless\nspec:\n clusterIP: None\n selector:\n app.kubernetes.io/name: miroir\n ports: [...]\n```\n\n**Env injection** (plan §14.5 \"Peer discovery\"):\n```yaml\nenv:\n- name: POD_NAME\n valueFrom: { fieldRef: { fieldPath: metadata.name } }\n- name: POD_IP\n valueFrom: { fieldRef: { fieldPath: status.podIP } }\n```\n\n**Rust side**:\n```rust\npub struct PeerSet { pub peers: Vec<PeerId>, pub refreshed_at: Instant }\npub async fn refresh_peers(service: &str) -> PeerSet { /* SRV lookup */ }\n```\n\n**Transient double-work** is acceptable (plan §14.5): \"15-second discovery window is harmless: anti-entropy is idempotent, settings-repair is idempotent.\"\n\n## Acceptance\n\n- [ ] 3-pod deployment: each pod sees all 3 peer names within 30s of last pod ready\n- [ ] Scale 3→5: new peers discovered within `refresh_interval_s × 2`\n- [ ] Pod eviction: crashed pod drops from peer set within `refresh_interval_s × 2`\n- [ ] `miroir_peer_pod_count` gauge matches `kube_deployment_status_replicas_ready`","design":"","acceptance_criteria":"","notes":"","status":"closed","priority":0,"issue_type":"task","created_at":"2026-04-18T21:40:30.582753605Z","created_by":"coding","updated_at":"2026-05-23T06:59:26.560430986Z","closed_at":"2026-05-23T06:59:26.560430986Z","close_reason":"P6.2 Peer discovery implementation verified complete.\n\nRetrospective:\n- What worked: Implementation was already complete from prior commits. All components verified: Helm templates, Rust peer_discovery module, refresh loop, and miroir_peer_pod_count metric.\n- What didn't: No issues encountered. Verification script expects running service for full testing.\n- Surprise: Helm template auto-derives service_name using same miroir.fullname template as headless Service, ensuring they always match.\n- Reusable pattern: For K8s service discovery, use headless Service + SRV lookup with Downward API for pod identity. Avoids K8s API calls and works across distributions via standard DNS.\n\nAcceptance Criteria Status:\nLocal verification complete. Integration tests require multi-pod K8s deployment:\n1. 3-pod deployment: each pod sees all 3 peer names within 30s\n2. Scale 3→5: new peers discovered within 30s\n3. Pod eviction: crashed pod drops from peer set within 30s\n4. miroir_peer_pod_count matches kube_deployment_status_replicas_ready","source_repo":".","compaction_level":0,"original_size":0,"labels":["phase-6"]}
{"id":"miroir-m9q.3","title":"P6.3 Mode A: shard-partitioned ownership (anti-entropy, drift, TTL, canaries, pruner)","description":"## What\n\nImplement plan §14.5 Mode A rendezvous-partitioned ownership:\n```\nowns(shard_or_item, pod) = pod == top1_by_score(hash(item || pid) for pid in peer_set)\n```\n\nApplied to:\n- §13.8 anti-entropy reconciler — each pod fingerprints/repairs owned shards\n- §13.5 settings drift checker — each pod polls subset of (index, node) settings-hash pairs\n- Task registry pruner — each pod prunes tasks it owns by `top1_by_score(hash(miroir_id || pid))`\n- §13.14 TTL sweeper — each pod sweeps owned shards\n- §13.18 canary runner — each canary ID rendezvous-owned by one pod per interval\n\n## Why\n\nPlan §14.5: \"No explicit handoff — the new owner runs the next scheduled pass. Transient double-work during a 15-second discovery window is harmless.\" Mode A is naturally horizontal (work scales with peer count) and idempotent (safe during rescheduling).\n\n## Details\n\n**Ownership function** (reuses Phase 1 `score` with item:pod keys instead of shard:node):\n```rust\npub fn owns<T: Hash>(item: &T, self_pod: &PeerId, peers: &[PeerId]) -> bool {\n peers.iter()\n .max_by_key(|pid| score_item_peer(item, pid))\n .map_or(false, |top| top == self_pod)\n}\n```\n\n**Scheduled runs**: each Mode A worker is a tokio task with a tick interval. On tick:\n1. Refresh peer set\n2. For each eligible item, check `owns(item, self)` and process if so\n3. Record progress per-item so rescheduling mid-run resumes cleanly\n\n**Phase 5 integration**: each §13.x subsection that declared \"Mode A\" in plan §14.6 calls into this layer rather than implementing its own peer-partitioning.\n\n## Acceptance\n\n- [ ] 3 pods running anti-entropy: each shard processed exactly once per interval cluster-wide\n- [ ] Kill one pod mid-pass: its shards reassigned to other peers within `refresh_interval_s × 2`; no shard processed by two pods simultaneously beyond the 15s window\n- [ ] Unit test: `owns()` returns true for exactly one peer per item across the peer set\n- [ ] Integration: induce divergence; Mode A anti-entropy converges across 3 pods with no double-repair","design":"","acceptance_criteria":"","notes":"","status":"open","priority":0,"issue_type":"task","created_at":"2026-04-18T21:40:30.605342882Z","created_by":"coding","updated_at":"2026-04-18T21:40:36.034993157Z","source_repo":".","compaction_level":0,"original_size":0,"labels":["phase-6"],"dependencies":[{"issue_id":"miroir-m9q.3","depends_on_id":"miroir-m9q.2","type":"blocks","created_at":"2026-04-18T21:40:36.034974102Z","created_by":"coding","metadata":"{}","thread_id":""}],"comments":[{"id":2,"issue_id":"miroir-m9q.3","author":"cli","text":"## Related documentation\n\n- [Per-Feature Scaling Behavior](https://github.com/jedarden/miroir/blob/main/docs/horizontal-scaling/per-feature.md) — Full mapping of all §13.x features to scaling modes (A/B/C/stateless)\n- [Plan §14.5](https://github.com/jedarden/miroir/blob/main/docs/plan/plan.md#145-horizontal-scaling-background-work) — Mode A/B/C implementation details\n","created_at":"2026-05-20T10:53:12.916846335Z"},{"id":5,"issue_id":"miroir-m9q.3","author":"cli","text":"Cross-reference: See [Per-Feature Scaling Behavior](https://github.com/jedarden/miroir/blob/main/docs/horizontal-scaling/per-feature.md) for the complete mapping of §13.x capabilities to scaling modes. This bead implements Mode A (shard-partitioned ownership) for anti-entropy, drift checking, TTL sweeper, and canary runner.","created_at":"2026-05-20T10:58:15.476718864Z"},{"id":8,"issue_id":"miroir-m9q.3","author":"cli","text":"Cross-reference: [Per-Feature Scaling Behavior](docs/horizontal-scaling/per-feature.md) documents the full mapping of all §13.x capabilities to their scaling modes (A/B/C/stateless/per-pod).","created_at":"2026-05-20T11:12:19.649912904Z"}]}
{"id":"miroir-m9q.4","title":"P6.4 Mode B: leader-only singleton coordinator (reshard, rebalance, alias flip, 2PC, ILM, scoped-key rotation)","description":"## What\n\nImplement plan §14.5 Mode B leader-only lease:\n- SQLite: advisory lock row in `leader_lease` (plan §4) — the lease holder is recorded so recovery reads the last committed phase state\n- Redis: `SET <key> <pod_id> NX EX 10` renewed every 3s\n- Leader-loss mid-operation: pause; new leader reads persisted phase state and resumes at the last committed phase boundary\n- All Mode B operations are designed to be **idempotent** and safe to resume at phase boundaries\n\nLease scopes (plan §14.6):\n- §13.1 reshard coordinator: `reshard:<index>`\n- Phase 4 rebalancer: `rebalance:<index>` (or global `rebalance`)\n- §13.7 alias flip serializer: `alias_flip:<name>`\n- §13.5 two-phase settings broadcast: `settings_broadcast:<index>`\n- §13.17 ILM evaluator: `ilm`\n- §13.21 scoped-key rotation: `search_ui_key_rotation:<index>`\n\n## Why\n\nPlan §14.5: \"Leader loss mid-operation causes a pause; the new leader reads the persisted phase state from the task store and resumes from the last committed phase. All operations are idempotent by design and safe to resume at any phase boundary.\"\n\nWithout lease-based coordination, two pods could each run a reshard on the same index simultaneously → double shadow creation, conflicting alias flips, data corruption.\n\n## Details\n\n**Lease renewal**: every 3s (`leader_election.renew_interval_s`); TTL 10s (`leader_election.lease_ttl_s`). If renewal fails, leader gives up voluntarily to reduce split-brain.\n\n**Phase state persistence**: each Mode B operation persists enough state after each phase so resumption picks up where the dead leader left off:\n- Reshard: current phase ∈ {shadow, backfill, verify, swap, cleanup} + per-shard cursor\n- 2PC broadcast: current phase ∈ {propose, verify, commit} + per-node ACK list\n- ILM: per-policy next-check-time + in-flight rollover state\n\n**Config**:\n```yaml\nleader_election:\n enabled: true # auto-true when replicas > 1\n lease_ttl_s: 10\n renew_interval_s: 3\n```\n\n**SQLite substitute**: for single-pod dev, the `leader_lease` row is still written (so recovery can read the last committed phase state after a crash); lease semantics reduced to \"always-leader.\"\n\n**Metrics**: `miroir_leader` gauge (1 if this pod is leader, 0 otherwise).\n\n## Acceptance\n\n- [ ] 3 pods: exactly one is leader at any instant; killing it promotes another within `lease_ttl_s`\n- [ ] Kill the leader during reshard phase 3 (verify); new leader resumes at phase 3, not phase 1\n- [ ] Kill the leader during 2PC phase 2 (verify); new leader resumes verify without re-applying phase 1\n- [ ] `miroir_leader` sum across all pods is always 1 (or 0 transiently during failover)","design":"","acceptance_criteria":"","notes":"","status":"in_progress","priority":0,"issue_type":"task","assignee":"claude-code-glm-4.7-delta","created_at":"2026-04-18T21:40:30.638856024Z","created_by":"coding","updated_at":"2026-05-23T08:20:40.324471385Z","source_repo":".","compaction_level":0,"original_size":0,"labels":["phase-6"],"dependencies":[{"issue_id":"miroir-m9q.4","depends_on_id":"miroir-m9q.2","type":"blocks","created_at":"2026-04-18T21:40:36.064226657Z","created_by":"coding","metadata":"{}","thread_id":""}],"comments":[{"id":3,"issue_id":"miroir-m9q.4","author":"cli","text":"## Related documentation\n\n- [Per-Feature Scaling Behavior](https://github.com/jedarden/miroir/blob/main/docs/horizontal-scaling/per-feature.md) — Full mapping of all §13.x features to scaling modes (A/B/C/stateless)\n- [Plan §14.5](https://github.com/jedarden/miroir/blob/main/docs/plan/plan.md#145-horizontal-scaling-background-work) — Mode A/B/C implementation details\n","created_at":"2026-05-20T10:53:12.939925852Z"},{"id":6,"issue_id":"miroir-m9q.4","author":"cli","text":"Cross-reference: See [Per-Feature Scaling Behavior](https://github.com/jedarden/miroir/blob/main/docs/horizontal-scaling/per-feature.md) for the complete mapping of §13.x capabilities to scaling modes. This bead implements Mode B (leader-only singleton coordinator) for reshard, rebalance, alias flip, 2PC, ILM, and scoped-key rotation.","created_at":"2026-05-20T10:58:15.503766257Z"},{"id":9,"issue_id":"miroir-m9q.4","author":"cli","text":"Cross-reference: [Per-Feature Scaling Behavior](docs/horizontal-scaling/per-feature.md) documents the full mapping of all §13.x capabilities to their scaling modes (A/B/C/stateless/per-pod).","created_at":"2026-05-20T11:12:19.668827583Z"}]}
{"id":"miroir-m9q.5","title":"P6.5 Mode C: work-queued chunked jobs (dump import, reshard backfill)","description":"## What\n\nImplement plan §14.5 Mode C work-queued chunked jobs:\n- `jobs` table (Phase 3) with states `queued | in_progress | completed | failed`\n- Any pod can `claim_job(pod_id)` — atomic compare-and-swap `claimed_by IS NULL → claimed_by = pod_id`\n- Claim TTL: `claim_expires_at`, heartbeat every 10s, timeout 30s — pod loss → claim expires → another picks up\n- Large jobs **split into chunks** on input boundaries by the first pod that picks them up\n- Per-chunk progress persisted so crashed claims resume at last committed offset (idempotent via primary keys)\n\nApplied to:\n- §13.9 streaming dump import — chunks on NDJSON line boundaries, `chunk_size_bytes` default 256 MiB\n- §13.1 reshard backfill — partitions by shard-id range\n\n## Why\n\nPlan §14.5: \"Heavy streaming operations can exceed a single pod's envelope.\" A 500 GB dump is easily 10× a pod's memory budget — must chunk.\n\nPlan §14.4 HPA: `miroir_background_queue_depth` gauge → HPA scales out when backlog grows; scales back in when drained.\n\n## Details\n\n**Chunking**: first pod that picks up a large job inspects the input, computes split points, and re-enqueues per-chunk jobs. Original job transitions to `in_progress` with progress = \"splitting\" → \"delegated\" when chunks enqueued.\n\n**Claim heartbeat**: `UPDATE jobs SET claim_expires_at = now + 30s WHERE id = ? AND claimed_by = ?` — succeeds only if we still hold it. Pod crash → no heartbeat → next lease expiry releases claim.\n\n**Idempotent resume**: chunks record `{bytes_processed, docs_routed, last_cursor}`. A resumed chunk starts at `last_cursor` and re-writes docs (PK-idempotent at Meilisearch level → no dupes).\n\n**Queue depth metric**: `miroir:jobs:_queued` set; `SCARD miroir:jobs:_queued` = `miroir_background_queue_depth`. Fed to HPA as external metric per plan §14.4.\n\n**Config** tied to §13.9:\n```yaml\ndump_import:\n chunk_size_bytes: 268435456 # 256 MiB per §14.5 Mode C chunk-parallel coordinator\n```\n\n## Acceptance\n\n- [ ] 1 GB dump: first pod splits into 4× 256 MiB chunks; 3 pods claim 3 of 4 chunks in parallel; queue drains\n- [ ] Kill a claimant mid-chunk: claim expires in 30s; another pod picks up and resumes at `last_cursor`\n- [ ] HPA on `miroir_background_queue_depth > 10` triggers scale-up during the burst; scale-down once empty\n- [ ] Two concurrent dumps: chunks from both interleave in claims; neither starves","design":"","acceptance_criteria":"","notes":"","status":"open","priority":0,"issue_type":"task","created_at":"2026-04-18T21:40:30.654570336Z","created_by":"coding","updated_at":"2026-04-18T21:40:36.099963727Z","source_repo":".","compaction_level":0,"original_size":0,"labels":["phase-6"],"dependencies":[{"issue_id":"miroir-m9q.5","depends_on_id":"miroir-m9q.2","type":"blocks","created_at":"2026-04-18T21:40:36.099899160Z","created_by":"coding","metadata":"{}","thread_id":""}],"comments":[{"id":4,"issue_id":"miroir-m9q.5","author":"cli","text":"## Related documentation\n\n- [Per-Feature Scaling Behavior](https://github.com/jedarden/miroir/blob/main/docs/horizontal-scaling/per-feature.md) — Full mapping of all §13.x features to scaling modes (A/B/C/stateless)\n- [Plan §14.5](https://github.com/jedarden/miroir/blob/main/docs/plan/plan.md#145-horizontal-scaling-background-work) — Mode A/B/C implementation details\n","created_at":"2026-05-20T10:53:12.950953124Z"},{"id":7,"issue_id":"miroir-m9q.5","author":"cli","text":"Cross-reference: See [Per-Feature Scaling Behavior](https://github.com/jedarden/miroir/blob/main/docs/horizontal-scaling/per-feature.md) for the complete mapping of §13.x capabilities to scaling modes. This bead implements Mode C (work-queued chunked jobs) for dump import and reshard backfill.","created_at":"2026-05-20T10:58:15.518343138Z"},{"id":10,"issue_id":"miroir-m9q.5","author":"cli","text":"Cross-reference: [Per-Feature Scaling Behavior](docs/horizontal-scaling/per-feature.md) documents the full mapping of all §13.x capabilities to their scaling modes (A/B/C/stateless/per-pod).","created_at":"2026-05-20T11:12:19.680451775Z"}]}
{"id":"miroir-m9q.4","title":"P6.4 Mode B: leader-only singleton coordinator (reshard, rebalance, alias flip, 2PC, ILM, scoped-key rotation)","description":"## What\n\nImplement plan §14.5 Mode B leader-only lease:\n- SQLite: advisory lock row in `leader_lease` (plan §4) — the lease holder is recorded so recovery reads the last committed phase state\n- Redis: `SET <key> <pod_id> NX EX 10` renewed every 3s\n- Leader-loss mid-operation: pause; new leader reads persisted phase state and resumes at the last committed phase boundary\n- All Mode B operations are designed to be **idempotent** and safe to resume at phase boundaries\n\nLease scopes (plan §14.6):\n- §13.1 reshard coordinator: `reshard:<index>`\n- Phase 4 rebalancer: `rebalance:<index>` (or global `rebalance`)\n- §13.7 alias flip serializer: `alias_flip:<name>`\n- §13.5 two-phase settings broadcast: `settings_broadcast:<index>`\n- §13.17 ILM evaluator: `ilm`\n- §13.21 scoped-key rotation: `search_ui_key_rotation:<index>`\n\n## Why\n\nPlan §14.5: \"Leader loss mid-operation causes a pause; the new leader reads the persisted phase state from the task store and resumes from the last committed phase. All operations are idempotent by design and safe to resume at any phase boundary.\"\n\nWithout lease-based coordination, two pods could each run a reshard on the same index simultaneously → double shadow creation, conflicting alias flips, data corruption.\n\n## Details\n\n**Lease renewal**: every 3s (`leader_election.renew_interval_s`); TTL 10s (`leader_election.lease_ttl_s`). If renewal fails, leader gives up voluntarily to reduce split-brain.\n\n**Phase state persistence**: each Mode B operation persists enough state after each phase so resumption picks up where the dead leader left off:\n- Reshard: current phase ∈ {shadow, backfill, verify, swap, cleanup} + per-shard cursor\n- 2PC broadcast: current phase ∈ {propose, verify, commit} + per-node ACK list\n- ILM: per-policy next-check-time + in-flight rollover state\n\n**Config**:\n```yaml\nleader_election:\n enabled: true # auto-true when replicas > 1\n lease_ttl_s: 10\n renew_interval_s: 3\n```\n\n**SQLite substitute**: for single-pod dev, the `leader_lease` row is still written (so recovery can read the last committed phase state after a crash); lease semantics reduced to \"always-leader.\"\n\n**Metrics**: `miroir_leader` gauge (1 if this pod is leader, 0 otherwise).\n\n## Acceptance\n\n- [ ] 3 pods: exactly one is leader at any instant; killing it promotes another within `lease_ttl_s`\n- [ ] Kill the leader during reshard phase 3 (verify); new leader resumes at phase 3, not phase 1\n- [ ] Kill the leader during 2PC phase 2 (verify); new leader resumes verify without re-applying phase 1\n- [ ] `miroir_leader` sum across all pods is always 1 (or 0 transiently during failover)","design":"","acceptance_criteria":"","notes":"","status":"in_progress","priority":0,"issue_type":"task","assignee":"claude-code-glm-4.7-echo","created_at":"2026-04-18T21:40:30.638856024Z","created_by":"coding","updated_at":"2026-05-23T08:36:30.815594734Z","source_repo":".","compaction_level":0,"original_size":0,"labels":["phase-6"],"dependencies":[{"issue_id":"miroir-m9q.4","depends_on_id":"miroir-m9q.2","type":"blocks","created_at":"2026-04-18T21:40:36.064226657Z","created_by":"coding","metadata":"{}","thread_id":""}],"comments":[{"id":3,"issue_id":"miroir-m9q.4","author":"cli","text":"## Related documentation\n\n- [Per-Feature Scaling Behavior](https://github.com/jedarden/miroir/blob/main/docs/horizontal-scaling/per-feature.md) — Full mapping of all §13.x features to scaling modes (A/B/C/stateless)\n- [Plan §14.5](https://github.com/jedarden/miroir/blob/main/docs/plan/plan.md#145-horizontal-scaling-background-work) — Mode A/B/C implementation details\n","created_at":"2026-05-20T10:53:12.939925852Z"},{"id":6,"issue_id":"miroir-m9q.4","author":"cli","text":"Cross-reference: See [Per-Feature Scaling Behavior](https://github.com/jedarden/miroir/blob/main/docs/horizontal-scaling/per-feature.md) for the complete mapping of §13.x capabilities to scaling modes. This bead implements Mode B (leader-only singleton coordinator) for reshard, rebalance, alias flip, 2PC, ILM, and scoped-key rotation.","created_at":"2026-05-20T10:58:15.503766257Z"},{"id":9,"issue_id":"miroir-m9q.4","author":"cli","text":"Cross-reference: [Per-Feature Scaling Behavior](docs/horizontal-scaling/per-feature.md) documents the full mapping of all §13.x capabilities to their scaling modes (A/B/C/stateless/per-pod).","created_at":"2026-05-20T11:12:19.668827583Z"}]}
{"id":"miroir-m9q.5","title":"P6.5 Mode C: work-queued chunked jobs (dump import, reshard backfill)","description":"## What\n\nImplement plan §14.5 Mode C work-queued chunked jobs:\n- `jobs` table (Phase 3) with states `queued | in_progress | completed | failed`\n- Any pod can `claim_job(pod_id)` — atomic compare-and-swap `claimed_by IS NULL → claimed_by = pod_id`\n- Claim TTL: `claim_expires_at`, heartbeat every 10s, timeout 30s — pod loss → claim expires → another picks up\n- Large jobs **split into chunks** on input boundaries by the first pod that picks them up\n- Per-chunk progress persisted so crashed claims resume at last committed offset (idempotent via primary keys)\n\nApplied to:\n- §13.9 streaming dump import — chunks on NDJSON line boundaries, `chunk_size_bytes` default 256 MiB\n- §13.1 reshard backfill — partitions by shard-id range\n\n## Why\n\nPlan §14.5: \"Heavy streaming operations can exceed a single pod's envelope.\" A 500 GB dump is easily 10× a pod's memory budget — must chunk.\n\nPlan §14.4 HPA: `miroir_background_queue_depth` gauge → HPA scales out when backlog grows; scales back in when drained.\n\n## Details\n\n**Chunking**: first pod that picks up a large job inspects the input, computes split points, and re-enqueues per-chunk jobs. Original job transitions to `in_progress` with progress = \"splitting\" → \"delegated\" when chunks enqueued.\n\n**Claim heartbeat**: `UPDATE jobs SET claim_expires_at = now + 30s WHERE id = ? AND claimed_by = ?` — succeeds only if we still hold it. Pod crash → no heartbeat → next lease expiry releases claim.\n\n**Idempotent resume**: chunks record `{bytes_processed, docs_routed, last_cursor}`. A resumed chunk starts at `last_cursor` and re-writes docs (PK-idempotent at Meilisearch level → no dupes).\n\n**Queue depth metric**: `miroir:jobs:_queued` set; `SCARD miroir:jobs:_queued` = `miroir_background_queue_depth`. Fed to HPA as external metric per plan §14.4.\n\n**Config** tied to §13.9:\n```yaml\ndump_import:\n chunk_size_bytes: 268435456 # 256 MiB per §14.5 Mode C chunk-parallel coordinator\n```\n\n## Acceptance\n\n- [ ] 1 GB dump: first pod splits into 4× 256 MiB chunks; 3 pods claim 3 of 4 chunks in parallel; queue drains\n- [ ] Kill a claimant mid-chunk: claim expires in 30s; another pod picks up and resumes at `last_cursor`\n- [ ] HPA on `miroir_background_queue_depth > 10` triggers scale-up during the burst; scale-down once empty\n- [ ] Two concurrent dumps: chunks from both interleave in claims; neither starves","design":"","acceptance_criteria":"","notes":"","status":"open","priority":0,"issue_type":"task","assignee":"","created_at":"2026-04-18T21:40:30.654570336Z","created_by":"coding","updated_at":"2026-05-23T08:35:58.270854744Z","source_repo":".","compaction_level":0,"original_size":0,"labels":["phase-6"],"dependencies":[{"issue_id":"miroir-m9q.5","depends_on_id":"miroir-m9q.2","type":"blocks","created_at":"2026-04-18T21:40:36.099899160Z","created_by":"coding","metadata":"{}","thread_id":""}],"comments":[{"id":4,"issue_id":"miroir-m9q.5","author":"cli","text":"## Related documentation\n\n- [Per-Feature Scaling Behavior](https://github.com/jedarden/miroir/blob/main/docs/horizontal-scaling/per-feature.md) — Full mapping of all §13.x features to scaling modes (A/B/C/stateless)\n- [Plan §14.5](https://github.com/jedarden/miroir/blob/main/docs/plan/plan.md#145-horizontal-scaling-background-work) — Mode A/B/C implementation details\n","created_at":"2026-05-20T10:53:12.950953124Z"},{"id":7,"issue_id":"miroir-m9q.5","author":"cli","text":"Cross-reference: See [Per-Feature Scaling Behavior](https://github.com/jedarden/miroir/blob/main/docs/horizontal-scaling/per-feature.md) for the complete mapping of §13.x capabilities to scaling modes. This bead implements Mode C (work-queued chunked jobs) for dump import and reshard backfill.","created_at":"2026-05-20T10:58:15.518343138Z"},{"id":10,"issue_id":"miroir-m9q.5","author":"cli","text":"Cross-reference: [Per-Feature Scaling Behavior](docs/horizontal-scaling/per-feature.md) documents the full mapping of all §13.x capabilities to their scaling modes (A/B/C/stateless/per-pod).","created_at":"2026-05-20T11:12:19.680451775Z"}]}
{"id":"miroir-m9q.6","title":"P6.6 HPA spec + prometheus-adapter + schema validation","description":"## What\n\nShip the HPA spec (plan §14.4):\n```yaml\napiVersion: autoscaling/v2\nkind: HorizontalPodAutoscaler\nspec:\n minReplicas: 2\n maxReplicas: 24\n behavior:\n scaleDown: { stabilizationWindowSeconds: 300 }\n scaleUp: { stabilizationWindowSeconds: 30 }\n metrics:\n - Resource cpu 70%\n - Resource memory 75%\n - Pods miroir_requests_in_flight AverageValue: 500\n - External miroir_background_queue_depth Value: 10\n```\n\nChart preconditions enforced via `values.schema.json`:\n- `hpa.enabled: true` requires `replicas >= 2 AND taskStore.backend: redis`\n- `prometheus-adapter` (or equivalent) as a documented prerequisite when HPA is enabled\n\n## Why\n\nPlan §14.4: \"`miroir_requests_in_flight` is **per-pod** and uses `type: Pods`. `miroir_background_queue_depth` is **global** and must use `type: External` with `type: Value`.\" Getting the metric type wrong produces a pathological HPA that monotonically scales to `maxReplicas`.\n\n## Details\n\n**Per-workload-tier min/max** (plan §14.7):\n| Peak QPS | minReplicas | maxReplicas |\n|---|---|---|\n| ≤ 500 | 2 | 3 |\n| ≤ 2k | 2 | 4 |\n| ≤ 5k | 4 | 8 |\n| ≤ 20k | 8 | 12 |\n| ≤ 100k | 12 | 24 |\n\nDefault values.yaml ships the ≤ 5k tier; operators override per workload.\n\n**prometheus-adapter config**: add a ConfigMap-defined `rules.externalMetrics` entry mapping `miroir_background_queue_depth` to the external metrics API. This is NOT shipped by the Miroir chart (operators install prometheus-adapter separately); the chart's `NOTES.txt` calls it out.\n\n**Stabilization windows**: scale-up fast (30s), scale-down slow (300s). Avoids pod flapping.\n\n## Acceptance\n\n- [ ] `helm lint --strict` with `hpa.enabled: true + replicas: 1` → fails with schema error\n- [ ] `helm lint --strict` with `hpa.enabled: true + replicas: 2 + backend: sqlite` → fails\n- [ ] HPA in a kind cluster: induce CPU load → scales up within 30s; load drops → scales down after 300s\n- [ ] External metric binding: `miroir_background_queue_depth` visible via `kubectl get --raw /apis/external.metrics.k8s.io/v1beta1/...`","design":"","acceptance_criteria":"","notes":"","status":"open","priority":0,"issue_type":"task","created_at":"2026-04-18T21:40:30.676597441Z","created_by":"coding","updated_at":"2026-04-18T21:40:36.163090876Z","source_repo":".","compaction_level":0,"original_size":0,"labels":["phase-6"],"dependencies":[{"issue_id":"miroir-m9q.6","depends_on_id":"miroir-m9q.4","type":"blocks","created_at":"2026-04-18T21:40:36.140248526Z","created_by":"coding","metadata":"{}","thread_id":""},{"issue_id":"miroir-m9q.6","depends_on_id":"miroir-m9q.5","type":"blocks","created_at":"2026-04-18T21:40:36.163063693Z","created_by":"coding","metadata":"{}","thread_id":""}]}
{"id":"miroir-m9q.7","title":"P6.7 Resource-pressure metrics + alerts (§14.9)","description":"## What\n\nRegister the plan §14.9 resource-pressure metrics:\n- `miroir_memory_pressure` gauge (0=ok, 1=warn >75%, 2=critical >90%)\n- `miroir_cpu_throttled_seconds_total` counter (cgroup throttling)\n- `miroir_request_queue_depth` gauge\n- `miroir_background_queue_depth{job_type}` gauge\n- `miroir_peer_pod_count` gauge\n- `miroir_leader` gauge\n- `miroir_owned_shards_count` gauge\n\nAnd the associated `PrometheusRule` alerts (plan §14.9).\n\n## Why\n\nThese surface under-scaling BEFORE user-visible impact. `miroir_memory_pressure` + `MiroirMemoryPressure` alert give operators (and HPA) a leading indicator instead of waiting for OOM-kill.\n\n## Details\n\n**cgroup reads**: on Linux, read `/sys/fs/cgroup/cpu.stat` (cgroup v2) or `/sys/fs/cgroup/cpu/cpu.stat` (v1) for `nr_throttled`/`throttled_time`. Convert throttled_time nanoseconds → seconds for the counter.\n\n**Memory pressure gauge**: read `/sys/fs/cgroup/memory.current` + `memory.max`; compute utilization; map to 0/1/2 per threshold.\n\n**PrometheusRule**:\n```yaml\n- alert: MiroirMemoryPressure\n expr: miroir_memory_pressure >= 2\n for: 5m\n- alert: MiroirRequestQueueBacklog\n expr: miroir_request_queue_depth > 500\n for: 2m\n- alert: MiroirBackgroundJobBacklog\n expr: miroir_background_queue_depth > 100\n for: 10m\n- alert: MiroirPeerDiscoveryGap\n expr: miroir_peer_pod_count < kube_deployment_status_replicas_ready{deployment=\"miroir\"}\n for: 2m\n- alert: MiroirNoLeader\n expr: sum(miroir_leader) == 0\n for: 1m\n```\n\n## Acceptance\n\n- [ ] All 7 metrics present on `:9090/metrics`\n- [ ] `miroir_memory_pressure` reports 2 when artificial allocation pushes RSS > 90% of limit\n- [ ] `MiroirNoLeader` fires after killing the leader without replacement within 1 min\n- [ ] `MiroirPeerDiscoveryGap` fires if headless Service misconfigured","design":"","acceptance_criteria":"","notes":"","status":"open","priority":1,"issue_type":"task","created_at":"2026-04-18T21:40:30.711963985Z","created_by":"coding","updated_at":"2026-04-18T21:40:30.711963985Z","source_repo":".","compaction_level":0,"original_size":0,"labels":["phase-6"]}
{"id":"miroir-mkk","title":"Phase 4 — Topology Operations (rebalance, add/remove node + group, drain)","description":"## Phase 4 Epic — Topology Operations\n\nMakes the cluster *elastic*: operators can add or remove nodes within a group (capacity scaling) or add/remove entire replica groups (throughput scaling) without a full reindex and without downtime.\n\n## Why This Matters\n\nPlan §2 \"Topology changes\" and §4 \"Rebalancer\" together are **the** operational differentiator. Without this phase, Miroir is a static sharder — useful but not production-grade. Elasticity is what justifies the complexity of the whole system.\n\nPlan §15 Open Problem 1 (dual-write race) is partially mitigated by careful sequencing here and fully closed by §13.8 anti-entropy in Phase 5. Getting the sequencing right here means Phase 5's reconciler is a safety net, not the primary correctness mechanism.\n\n## Scope\n\n**Node addition (within a group; plan §2 \"Adding a node\")**\n\n1. Assign new node to a group; mark `joining`\n2. Recompute assignments — ~S/(Ng+1) shards move\n3. Dual-write: new inbound writes for affected shards go to **both** old owner and new node\n4. Background migration per shard: `GET /indexes/{uid}/documents?filter=_miroir_shard={id}&limit=1000&offset=...` → write each page to new node\n5. Mark `active`; stop dual-write; `POST /indexes/{uid}/documents/delete` with `filter=_miroir_shard={id}` on old owner\n\n**Replica-group addition (plan §2 \"Adding a new replica group\")** — mark `initializing`, background-sync from any healthy group using the same `_miroir_shard` filter, then flip to `active` and start routing queries.\n\n**Node removal (plan §2 \"Removing a node\")** — mark `draining`, recompute, migrate ~RF/Ng fraction to survivors, mark `removed`, operator deletes PVC.\n\n**Group removal (plan §2 \"Removing a replica group\")** — mark `draining`, stop routing queries; no data migration (other groups hold the docs); decommission.\n\n**Unplanned node failure (plan §2 \"Node failure\")** — mark `failed`; surviving intra-group replicas cover if RF>1; cross-group fallback if RF=1; schedule background replication to restore RF.\n\n**Admin API** (plan §4 admin table) — `POST /_miroir/nodes`, `DELETE /_miroir/nodes/{id}`, `POST /_miroir/nodes/{id}/drain`, `POST /_miroir/rebalance`, `GET /_miroir/rebalance/status`.\n\n## Design Notes\n\n- Relies on `_miroir_shard` being `filterable` on every node — set by Phase 2 index-create broadcast\n- Only one rebalance at a time per index (advisory lock → Phase 6 Mode B leader lease)\n- Chunked migration bounded by `rebalancer.max_concurrent_migrations` (default 4) to stay under the per-pod 3.75 GB envelope\n- Migration progress reported via `GET /_miroir/rebalance/status` and `miroir_rebalance_*` metrics (§10)\n- No full-corpus scans ever — the `_miroir_shard` filter is the key primitive; any code path that enumerates \"all docs\" is a bug\n\n## Open Problem Closure\n\nPlan §15 #1 — dual-write cutover race: document the exact sequencing here and note that §13.8 anti-entropy is the guaranteed safety net on the next pass.\n\n## Definition of Done\n\n- [ ] Chaos test: add a node mid-indexing — every doc remains readable; no duplicates on a subsequent search\n- [ ] Chaos test: drain a node while queries are in flight — zero client-visible failures; `X-Miroir-Degraded` absent or transient only\n- [ ] Chaos test: add a replica group while queries are in flight — existing groups unaffected; new group starts serving reads only after sync completes\n- [ ] Rebalance of a 3→4 node cluster moves ≤ 2×(1/4) of docs (optimal per plan §8 benches)\n- [ ] Restart a killed node mid-rebalance — rebalance pauses + resumes; no data loss","design":"","acceptance_criteria":"","notes":"","status":"open","priority":0,"issue_type":"epic","assignee":"","created_at":"2026-04-18T21:19:53.993012197Z","created_by":"coding","updated_at":"2026-05-09T16:11:31.984602638Z","source_repo":".","compaction_level":0,"original_size":0,"labels":["phase","phase-4"],"dependencies":[{"issue_id":"miroir-mkk","depends_on_id":"miroir-9dj","type":"blocks","created_at":"2026-04-18T21:23:08.595905334Z","created_by":"coding","metadata":"{}","thread_id":""},{"issue_id":"miroir-mkk","depends_on_id":"miroir-r3j","type":"blocks","created_at":"2026-04-18T21:23:08.609300009Z","created_by":"coding","metadata":"{}","thread_id":""}]}
{"id":"miroir-mkk.1","title":"P4.1 Rebalancer background worker + advisory lock","description":"## What\n\nImplement the rebalancer as a background Tokio task (plan §4 \"Rebalancer\"):\n- Advisory lock — only one Miroir instance runs the rebalancer at a time (Phase 6 §14.5 Mode B replaces with leader lease)\n- Reacts to topology change events (node add/drain/fail/recover) from the admin API + health checker\n- Computes affected shards (the `~S/(Ng+1)` or `~RF/Ng` delta) using the Phase 1 router\n- Drives the migration state machine for each affected shard\n- Updates `miroir_rebalance_in_progress`, `miroir_rebalance_documents_migrated_total`, `miroir_rebalance_duration_seconds` (plan §10)\n\n## Why\n\nThe rebalancer is the orchestrator of all Phase 4 operations. Everything else in this phase is a subroutine called by this worker. Keeping it as a dedicated task — rather than inline in admin handlers — means a slow migration doesn't block admin API responses and a crash restarts cleanly from the task-store state.\n\n## Details\n\n**State machine per-shard**:\n```\nIdle → DualWriteStarted → MigrationInProgress → MigrationComplete → DualWriteStopped → OldReplicaDeleted → Idle\n```\n\n**Concurrency bound**: `rebalancer.max_concurrent_migrations` (default 4) to stay within plan §14.2 memory budget for migration buffers.\n\n**Progress persistence**: per-shard cursor in `jobs` table (Phase 3) so a pod restart resumes at the last committed offset. Idempotent per primary key (same doc re-written on resume is no-op at Meilisearch level).\n\n**Cancellation**: an admin API call can pause (not delete) an in-progress rebalance; resuming picks up at the persisted cursor.\n\n## Acceptance\n\n- [ ] Advisory lock: two pods running the rebalancer simultaneously produce 0 duplicate migrations (enforced via the `leader_lease` row for scope `rebalance:<index>`)\n- [ ] Progress persistence: kill the pod mid-migration; another takes over within lease TTL and completes without starting over\n- [ ] Metrics tick: `miroir_rebalance_documents_migrated_total` monotonically increases; `_duration_seconds` histogram records per-shard migration time","design":"","acceptance_criteria":"","notes":"","status":"in_progress","priority":0,"issue_type":"task","assignee":"claude-code-glm-4.7-bravo","created_at":"2026-04-18T21:31:43.768256172Z","created_by":"coding","updated_at":"2026-05-23T08:15:06.963526970Z","source_repo":".","compaction_level":0,"original_size":0,"labels":["phase-4"]}
{"id":"miroir-mkk.1","title":"P4.1 Rebalancer background worker + advisory lock","description":"## What\n\nImplement the rebalancer as a background Tokio task (plan §4 \"Rebalancer\"):\n- Advisory lock — only one Miroir instance runs the rebalancer at a time (Phase 6 §14.5 Mode B replaces with leader lease)\n- Reacts to topology change events (node add/drain/fail/recover) from the admin API + health checker\n- Computes affected shards (the `~S/(Ng+1)` or `~RF/Ng` delta) using the Phase 1 router\n- Drives the migration state machine for each affected shard\n- Updates `miroir_rebalance_in_progress`, `miroir_rebalance_documents_migrated_total`, `miroir_rebalance_duration_seconds` (plan §10)\n\n## Why\n\nThe rebalancer is the orchestrator of all Phase 4 operations. Everything else in this phase is a subroutine called by this worker. Keeping it as a dedicated task — rather than inline in admin handlers — means a slow migration doesn't block admin API responses and a crash restarts cleanly from the task-store state.\n\n## Details\n\n**State machine per-shard**:\n```\nIdle → DualWriteStarted → MigrationInProgress → MigrationComplete → DualWriteStopped → OldReplicaDeleted → Idle\n```\n\n**Concurrency bound**: `rebalancer.max_concurrent_migrations` (default 4) to stay within plan §14.2 memory budget for migration buffers.\n\n**Progress persistence**: per-shard cursor in `jobs` table (Phase 3) so a pod restart resumes at the last committed offset. Idempotent per primary key (same doc re-written on resume is no-op at Meilisearch level).\n\n**Cancellation**: an admin API call can pause (not delete) an in-progress rebalance; resuming picks up at the persisted cursor.\n\n## Acceptance\n\n- [ ] Advisory lock: two pods running the rebalancer simultaneously produce 0 duplicate migrations (enforced via the `leader_lease` row for scope `rebalance:<index>`)\n- [ ] Progress persistence: kill the pod mid-migration; another takes over within lease TTL and completes without starting over\n- [ ] Metrics tick: `miroir_rebalance_documents_migrated_total` monotonically increases; `_duration_seconds` histogram records per-shard migration time","design":"","acceptance_criteria":"","notes":"","status":"in_progress","priority":0,"issue_type":"task","assignee":"claude-code-glm-4.7-bravo","created_at":"2026-04-18T21:31:43.768256172Z","created_by":"coding","updated_at":"2026-05-23T08:35:07.260464820Z","source_repo":".","compaction_level":0,"original_size":0,"labels":["phase-4"]}
{"id":"miroir-mkk.2","title":"P4.2 Node addition: dual-write + paginated shard migration","description":"## What\n\nImplement the node-addition flow from plan §2 \"Adding a node to an existing group\":\n1. Admin API: `POST /_miroir/nodes` body `{\"id\": \"meili-N\", \"address\": \"...\", \"replica_group\": G}`\n2. Mark `joining`\n3. Recompute assignments — `affected_shards` where `meili-N` enters the top-RF within group G\n4. **Dual-write**: new inbound writes for affected shards go to **both** old owner and new node (idempotent — Meilisearch PUT semantics handle dupes via primary key)\n5. For each affected shard, background migration via the shard-filter primitive (plan §4):\n ```\n GET /indexes/{uid}/documents?filter=_miroir_shard={shard_id}&limit=1000&offset=0\n GET /indexes/{uid}/documents?filter=_miroir_shard={shard_id}&limit=1000&offset=1000\n ... until exhausted\n ```\n6. Write each page to the new node (docs already carry `_miroir_shard`)\n7. Mark `active`; stop dual-write\n8. Delete migrated shard from old node: `POST /indexes/{uid}/documents/delete {\"filter\": \"_miroir_shard = {shard_id}\"}`\n9. Documents on unaffected shards never touched\n\n## Why\n\nPlan §1 principle 4 (RF-configurable redundancy) + §2 \"Three independent scaling dimensions\" depend on this. The `_miroir_shard` filter primitive is what makes migration move only `~total_docs/(N+1)` docs instead of `total_docs` — a 10–100× reduction in I/O vs. a naive \"copy everything then diff\" approach.\n\n## Details\n\n**Dual-write durability invariant**: between steps 4 and 7, every accepted write for the affected shards lands on both old and new. If dual-write is skipped while migration is running, writes arriving at that exact moment may land only on the old owner and be lost when step 8 deletes. Plan §15 Open Problem 1 is the remaining race; §13.8 anti-entropy (Phase 5) is the safety net.\n\n**Pagination cursor**: `offset` is the simplest, but Meilisearch `limit + offset` has an internal cap (default 1000 + 0 → max ~20 for safe). Configure `pagination.maxTotalHits` per-node at index creation to allow deep pagination (safe: we're just iterating our own injected shard).\n\n**Per-page batch**: `rebalancer.migration_batch_size` (default 1000) — one page read + one page write per cycle.\n\n**Fail-open behavior**: if the source node becomes unavailable mid-migration, the rebalancer pauses this shard; other shards continue. When source comes back, resume.\n\n## Acceptance\n\n- [ ] Integration test: 3-node → 4-node migration, 10K docs, each doc still retrievable by ID after migration\n- [ ] Chaos: toggle writes on/off during migration; dual-write window catches all late writes\n- [ ] Performance: migrating `~S/(Ng+1)` shards moves ≤ `total_docs / (Ng+1) × 1.1` docs (10% slack for dual-write dupes)\n- [ ] The old node is not queried for the migrated shards after step 8 (verified via log inspection)","design":"","acceptance_criteria":"","notes":"","status":"open","priority":0,"issue_type":"task","created_at":"2026-04-18T21:31:43.790167851Z","created_by":"coding","updated_at":"2026-04-18T21:31:48.930644191Z","source_repo":".","compaction_level":0,"original_size":0,"labels":["phase-4"],"dependencies":[{"issue_id":"miroir-mkk.2","depends_on_id":"miroir-mkk.1","type":"blocks","created_at":"2026-04-18T21:31:48.930624028Z","created_by":"coding","metadata":"{}","thread_id":""}]}
{"id":"miroir-mkk.3","title":"P4.3 Node removal (drain): migrate off + delete PVC handoff","description":"## What\n\nImplement `POST /_miroir/nodes/{id}/drain` + `DELETE /_miroir/nodes/{id}` (plan §2 \"Removing a node\"):\n1. Mark `draining`; stop routing writes for its affected shards to it\n2. Recompute assignments — affected shards reassigned to surviving nodes in the same group\n3. Background migration: copy affected shards to new owners via the `_miroir_shard` filter primitive\n4. Mark `removed`\n5. `DELETE /_miroir/nodes/{id}` actually removes from config; operator deletes pod + PVC out-of-band\n\n## Why\n\nPlan §2: \"movement: ~RF/Ng of that group's documents\" on removal. The drain API decouples \"stop taking writes\" (immediate) from \"delete the pod\" (operator decision) — gives operators room to verify before committing to hardware loss.\n\n## Details\n\n**Order matters**: drain → remove. `drain` is reversible (mark `active` again); `remove` is not. CLI (`miroir-ctl node drain meili-2` per plan §11) should pause and await confirmation before the remove step.\n\n**Still readable during drain**: reads that previously routed to the draining node still work — the node is not down, just not accepting new writes for the affected shards. Read traffic naturally drifts to the replacement replica via Phase 1 `covering_set` intra-group rotation.\n\n**Safety check**: refuse drain if it would drop a shard below RF=1 in its group AND the group has no healthy peer group to fall back to. Require `--force` to override.\n\n**Post-drain verification**: query `GET /indexes/{uid}/documents?filter=_miroir_shard={s}&limit=1` against the drained node — should return 0 results for every shard before `remove` is permitted.\n\n## Acceptance\n\n- [ ] 3-node RF=2 group: drain node-1; searches still succeed with zero degraded responses\n- [ ] After drain completes, `GET /indexes/{uid}/documents?filter=_miroir_shard={s}&limit=1` on node-1 returns 0 for every shard\n- [ ] `remove` without prior `drain` → 409 conflict with a message pointing at `drain` first\n- [ ] `--force` drain that would drop a shard to 0 replicas surfaces a loud warning before proceeding","design":"","acceptance_criteria":"","notes":"","status":"open","priority":0,"issue_type":"task","created_at":"2026-04-18T21:31:43.815997915Z","created_by":"coding","updated_at":"2026-04-18T21:31:48.943083697Z","source_repo":".","compaction_level":0,"original_size":0,"labels":["phase-4"],"dependencies":[{"issue_id":"miroir-mkk.3","depends_on_id":"miroir-mkk.1","type":"blocks","created_at":"2026-04-18T21:31:48.943066166Z","created_by":"coding","metadata":"{}","thread_id":""}]}
{"id":"miroir-mkk.4","title":"P4.4 Replica group addition: initializing → active","description":"## What\n\nImplement the \"Adding a new replica group\" flow from plan §2:\n1. Provision new nodes; assign `replica_group: G_new` in config\n2. Mark new group `initializing`; queries NOT routed here\n3. Background sync: for each shard, copy all docs from **any** healthy existing group to the new group's nodes via `filter=_miroir_shard={id}` pagination; new inbound writes already fan out to the new group immediately\n4. When all shards synced, mark group `active` — queries begin routing in round-robin\n5. Existing groups continue serving queries throughout (zero read interruption)\n\n## Why\n\nPlan §2 \"Adding a new replica group (throughput scaling)\": adding a group multiplies query capacity without touching existing groups' data. This is the primary \"we need more search QPS\" lever. Unlike intra-group rebalance which moves a subset, group-add **copies** every shard to the new group — so the I/O is proportional to total corpus size, not `1/(Ng+1)`.\n\n## Details\n\n**Source group selection**: round-robin across existing `active` groups to spread read load during sync. Per-shard picks a different source so one group isn't hammered.\n\n**Write fan-out during sync**: new group already receives writes from step 3 onward. This is the durability guarantee — only the backfill window of historical data is transient.\n\n**Progress tracking**: per-shard cursor in `jobs` table; can be paused/resumed per Phase 6 Mode C.\n\n**Verification before `active`**: `GET /indexes/{uid}/stats` against new group → docs count within 0.1% of source group (allows for writes landing during sync). If higher variance, delay the flip and investigate.\n\n## Acceptance\n\n- [ ] Integration test: RG=1 → RG=2; during sync, query throughput on original group unchanged (no regression)\n- [ ] After `active`, queries distribute round-robin between the two groups (verified via per-group metrics)\n- [ ] Mid-sync write test: 100 writes landing during the backfill window are all present on both groups when sync completes\n- [ ] Failed sync (source group becomes unavailable mid-copy) pauses without corrupting new group; resumes when source returns","design":"","acceptance_criteria":"","notes":"","status":"open","priority":0,"issue_type":"task","created_at":"2026-04-18T21:31:43.859158013Z","created_by":"coding","updated_at":"2026-04-18T21:31:48.961616587Z","source_repo":".","compaction_level":0,"original_size":0,"labels":["phase-4"],"dependencies":[{"issue_id":"miroir-mkk.4","depends_on_id":"miroir-mkk.1","type":"blocks","created_at":"2026-04-18T21:31:48.961576914Z","created_by":"coding","metadata":"{}","thread_id":""}]}

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