Task 66 — Абстракция mesh-бэкендов

Phase: 4 Initiative: 26 Status: done Owner: — Slug: mesh-backends-abstraction

Goal

Интерфейсы IMeshBus, ITaskQueue и IMeshStateStore отделяют mesh-оркестрацию от конкретных бэкендов. Single-host mesh продолжает работать с in-process очередями и SQLite по умолчанию. Бэкенды подключаются через dependency injection и не влияют на публичный API агента.

Acceptance criteria

• IMeshBus interface with Publish/Subscribe/RequestReply semantics
• ITaskQueue interface with Enqueue/Dequeue/Ack/DLQ semantics
• IMeshStateStore interface with Get/Set/CompareAndSet/Watch semantics
• InProcessMeshBus — Channel-based pub/sub + request/reply (default)
• InProcessTaskQueue — ConcurrentQueue-based task queue (default)
• InProcessMeshStateStore — ConcurrentDictionary-based state store (default)
• Interfaces live in src/agent/Mesh/Abstractions/
• In-process impls live in src/agent/Mesh/InProcess/
• All abstractions registered in MeshServiceCollectionExtensions
• Unit tests for all three interfaces covering happy path + error cases
• dotnet build passes; dotnet test passes

Sub-tasks (implementation checklist)

• Define IMeshBus with Publish/Subscribe/RequestReply/IsHealthy
• Define ITaskQueue with Enqueue/Dequeue/Ack/Fail/DLQ + MeshTask/QueuedTask records
• Define IMeshStateStore with Get/Set/CompareAndSet/Delete/Exists/Increment/Watch/ScanKeys/IsHealthy + StoredValue record
• Implement InProcessMeshBus (Channel-based pub/sub, ConcurrentDictionary subscribers, reply routing via TCS)
• Implement InProcessTaskQueue (ConcurrentQueue + Timer for visibility timeout, DLQ, retry with delay, ULID IDs)
• Implement InProcessMeshStateStore (ConcurrentDictionary + Timer for TTL cleanup, Channel for Watch)
• Register all three as singleton defaults in MeshServiceCollectionExtensions
• Write InProcessMeshBusTests (9 tests: BackendKind, IsHealthy, Publish, Subscribe fan-out, unsubscribe, RequestReply, timeout, Dispose)
• Write InProcessTaskQueueTests (14 tests: BackendKind, Enqueue, Dequeue, FIFO, Ack, Fail+retry, Fail→DLQ, DLQ read, IsHealthy, Dispose)
• Write InProcessMeshStateStoreTests (16 tests: BackendKind, Get/Set, CAS, Delete, Exists, Increment, Watch, ScanKeys, IsHealthy, Dispose)
• Fix bug: missing ScheduleReEnqueueAsync method in InProcessTaskQueue (broken ContinueWith state object)
• Fix bug: DLQ name mutation in FailAsync (queueName → queueName + "-dlq" caused _dlqs["dlq-q-dlq"] vs _dlqs["dlq-q-dlq-dlq"] mismatch)

Validation

dotnet build src/agent/Hercules.csproj  → 0 errors
dotnet test --filter "FullyQualifiedName~InProcess"
  → Passed: 42, Failed: 0

Completion note

Implemented three mesh backend abstractions (IMeshBus, ITaskQueue, IMeshStateStore) with in-process defaults:

• IMeshBus: Channel-based pub/sub + request/reply with correlation-ID routing via TaskCompletionSource
• ITaskQueue: ConcurrentQueue with visibility timeout via Timer, DLQ, retry with delay, ULID IDs; fixes: missing ScheduleReEnqueueAsync helper, DLQ key mutation causing wrong queue lookup
• IMeshStateStore: ConcurrentDictionary with version-based optimistic locking, TTL cleanup, Channel-based Watch
• All registered as singleton defaults in MeshServiceCollectionExtensions (lines 440-445)
• 42 unit tests covering happy path and error cases

Scope / Likely files

src/agent/Mesh/Abstractions/IMeshBus.cs, src/agent/Mesh/Abstractions/ITaskQueue.cs, src/agent/Mesh/Abstractions/IMeshStateStore.cs, src/agent/Mesh/InProcess/

Dependencies

• блокирует / опирается на: task_003 — hybrid-storage
• блокирует / опирается на: task_043 — mesh-router

Risks / Rollback

Утечка абстракций; минимальный набор методов, чёткие контракты, контрактные тесты на каждую реализацию.

Links

• Backlog: ../backlog.md
• Roadmap (EN): ../../ROADMAP-EN.md
• Roadmap (RU): ../../ROADMAP-RU.md