---
description: "Task list for Distributed KVS Consistency Modes"
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# Tasks: Distributed KVS Consistency Modes

**Input**: Design documents from `/specs/003-kvs-consistency/`  
**Prerequisites**: plan.md (required), spec.md (user stories), research.md, data-model.md, contracts/  

**Tests**: Required per constitution; include unit/integration tests for mode behaviors (strong/eventual), namespace config, convergence/recovery.

**Organization**: Tasks are grouped by user story to enable independent implementation and testing.

## Format: `[ID] [P?] [Story] Description`

- **[P]**: Can run in parallel (different files, no dependencies)
- **[Story]**: Which user story this task belongs to (e.g., US1, US2, US3)
- Include exact file paths in descriptions

## Phase 1: Setup (Shared Infrastructure)

**Purpose**: Prepare config and API surfaces for namespace-level consistency modes.

- [X] T001 Create namespace/mode config schema and defaults in `rdb-server/src/config/mod.rs`
- [X] T002 Update gRPC proto (if needed) to expose namespace/mode config endpoints in `rdb-proto/src/raft_server.proto`
- [X] T003 Add config loading/validation for namespace modes in `rdb-server/src/main.rs`

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## Phase 2: Foundational (Blocking Prerequisites)

**Purpose**: Core plumbing for mode-aware replication and observability hooks.

- [X] T004 Implement mode flag propagation to peers (strong/eventual per namespace) in `rdb-server/src/peer.rs`
- [X] T005 Add LWW conflict resolution helper for eventual mode in `rdb-server/src/peer.rs`
- [X] T006 Emit mode/lag/quorum metrics and structured logs in `rdb-server/src/raft_service.rs` and `rdb-server/src/peer.rs`

**Checkpoint**: Mode flags flow through storage/peers; metrics/log hooks in place.

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## Phase 3: User Story 1 - 強整合性クラスタを安全に稼働 (Priority: P1)

**Goal**: Quorum read/write with immediate visibility; reject writes without quorum.

### Tests
- [X] T007 [US1] Add strong-mode integration test (quorum write/read, node failure) in `rdb-server/tests/test_consistency.rs`

### Implementation
- [X] T008 [US1] Enforce quorum writes/reads for strong mode in `rdb-server/src/peer.rs`
- [X] T009 [US1] Return explicit errors on quorum deficit in strong mode in `rdb-server/src/raft_service.rs`

**Checkpoint**: Strong mode test passes; quorum enforcement confirmed.

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## Phase 4: User Story 2 - 結果整合性モードで高スループット運用 (Priority: P1)

**Goal**: Accept writes under partial availability; converge within target window using LWW.

### Tests
- [X] T010 [US2] Add eventual-mode integration test (delayed read then convergence) in `rdb-server/tests/test_consistency.rs`
- [X] T011 [P] [US2] Add partition/recovery test with LWW resolution in `rdb-server/tests/test_consistency.rs`

### Implementation
- [X] T012 [US2] Implement eventual-mode write acceptance with async replication in `rdb-server/src/peer.rs`
- [X] T013 [US2] Apply LWW conflict resolution on replay/sync in `rdb-server/src/peer.rs`
- [X] T014 [US2] Track and expose convergence lag metrics in `rdb-server/src/peer_manager.rs`

**Checkpoint**: Eventual mode converges within target window; LWW conflicts resolved.

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## Phase 5: User Story 3 - モード切替と運用観測 (Priority: P2)

**Goal**: Safe mode changes per namespace and clear observability/state reporting.

### Tests
- [X] T015 [US3] Add mode-switch test (namespace strong↔eventual, rolling apply) in `rdb-server/tests/test_consistency.rs`
- [X] T016 [US3] Add mismatch detection test for inconsistent mode configs in `rdb-server/tests/test_consistency.rs`

### Implementation
- [X] T017 [US3] Support mode configuration updates per namespace (reload/rolling) in `rdb-server/src/config/mod.rs`
- [X] T018 [US3] Expose mode state and mismatches via logs/metrics/optional gRPC in `rdb-server/src/raft_service.rs`
- [X] T019 [US3] Provide operator-facing quickstart/CLI instructions for mode ops in `specs/003-kvs-consistency/quickstart.md`

**Checkpoint**: Mode switches apply safely; operators can detect/report mismatches.

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## Phase 6: Polish & Cross-Cutting Concerns

**Purpose**: Hardening, docs, and verification scripts.

- [X] T020 Add contract/OpenAPI updates for mode/config endpoints in `specs/003-kvs-consistency/contracts/`
- [X] T021 Add data model definitions for ClusterConfig/ConsistencyPolicy/ReplicationState in `specs/003-kvs-consistency/data-model.md`
- [X] T022 Update verification script to cover mode tests in `scripts/verify-raft.sh`
- [X] T023 Run full workspace checks (`cargo fmt`, `cargo test -p rdb-server --tests`) and document results in `specs/003-kvs-consistency/quickstart.md`

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## Dependencies & Execution Order

- Phase 2 (Foundational) blocks all user stories.
- US1 (strong) and US2 (eventual) can proceed after foundational; US3 (mode ops) depends on config plumbing from Phases 1–2.
- Tests in each story precede implementation tasks.

## Parallel Examples

- T010 and T011 can run in parallel after T006 (tests for eventual mode scenarios).
- T012–T014 can run in parallel once T004–T006 are done (separate code paths for eventual replication and metrics).
- T018 and T019 can run in parallel after mode config plumbing (T017).

## Implementation Strategy

1. Lay config/API plumbing (Phases 1–2).
2. Deliver strong mode (US1) and eventual mode (US2) with tests.
3. Add mode switching/observability (US3).
4. Polish: contracts, data model docs, verification script, full test sweep.