[middleware] Cache (cache)

[FumingPower3925]

Cache Middleware (cache)

Response caching with pluggable store, built-in stampede prevention.

Config

• Store — pluggable cache store (default: sharded in-memory LRU)
• TTL — cache entry time-to-live
• KeyGenerator — function to derive cache key from request (default: method + path + sorted query)
• Singleflight — enable request coalescing on cache miss (default: true)
• X-Cache header — HIT or MISS

MemoryStore: Sharded LRU

1. Configurable number of shards (default: 16)
2. Each shard has its own sync.RWMutex + LRU list
3. Key hashed to select shard
4. Per-shard max entries; LRU eviction within each shard
5. Expired entries cleaned lazily on access + periodic sweep

Stampede Prevention (Singleflight)

When enabled (default), concurrent cache misses for the same key are coalesced using sync/singleflight.

API

• Invalidate(key string), InvalidatePrefix(prefix string)
• Store interface: Get(key) ([]byte, bool), Set(key, value, ttl), Delete(key), DeletePrefix(prefix)

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Migrated from goceleris/middlewares#20