zhenyi
1000f8a80d
- Add gRPC service modules: auth, channel, channel settings, member, permission - Update protobuf definitions and generated code - Remove immediate/ real-time module (superseded by IM service) - Update etcd discovery and registration - Update cache, error, config, and build infrastructure - Add ADR documentation - Update OpenAPI spec
1.4 KiB
1.4 KiB
ADR-002: 两级缓存架构 / Two-Tier Caching Architecture
状态 / Status
Accepted
日期 / Date: 2024-01-01
背景 / Context
平台需要缓存机制来减少数据库负载，提高响应速度。需要在性能和一致性之间取得平衡。
The platform needs a caching mechanism to reduce database load and improve response times. A balance between performance and consistency is required.
决策 / Decision
采用 两级缓存架构：L1 (内存 LRU-TTL) + L2 (Redis)。
Adopted two-tier caching: L1 (in-memory LRU-TTL) + L2 (Redis).
考虑的方案 / Considered Options
- 纯 Redis — 简单但网络延迟高
- 纯内存缓存 — 快但不跨实例共享
- 两级缓存 — 兼顾速度和共享
后果 / Consequences
正面 / Positive
- L1 提供极低延迟 / L1 provides ultra-low latency
- L2 提供跨实例共享 / L2 provides cross-instance sharing
- 减少数据库负载 / Reduces database load
负面 / Negative
- 缓存一致性复杂 / Cache consistency is complex
- 内存占用增加 / Increased memory usage
风险 / Risks
- 缓存雪崩 / Cache avalanche
- 缓存穿透 / Cache penetration
实现细节 / Implementation Details
- L1:
DashMap + Mutex<LruTracker>, TTL 5 分钟 - L2: Redis via r2d2, TTL 可配置
- 策略: L1 miss → L2 miss → 数据库查询