custom-backend

Custom Cache Backend Example

This example demonstrates how to create custom cache backends by implementing the httpcache.Cache interface.

Features Demonstrated

• StatsCache: Wrapper that adds statistics tracking (hits, misses, sets, deletes)
• TTLCache: Cache with automatic expiration based on time-to-live
• Decorator pattern for extending cache functionality
• Background cleanup for expired entries

Running the Example

From the project root directory:

go run ./examples/custom-backend/main.go

Or from the examples/custom-backend directory:

go run main.go

Cache Interface

To create a custom cache backend, implement this interface:

type Cache interface {
    Get(key string) (responseBytes []byte, ok bool)
    Set(key string, responseBytes []byte)
    Delete(key string)
}

Use Cases

Custom cache backends are useful for:

• Monitoring: Track cache hits/misses and performance
• Size limits: Implement LRU or LFU eviction policies
• TTL support: Automatic expiration independent of HTTP headers
• Compression: See CompressCache example for production-ready compression
• Encryption: Secure sensitive cached data
• Multi-tier: Combine multiple cache backends (e.g., memory + disk)
• Database: Store cache in PostgreSQL, MySQL, etc.

Pattern: Cache Wrapper

The decorator pattern allows you to add functionality without modifying the original cache:

type WrappedCache struct {
    underlying httpcache.Cache
    // ... additional fields
}

func (c *WrappedCache) Get(key string) ([]byte, bool) {
    // Add custom logic before/after
    return c.underlying.Get(key)
}

Example Implementations

1. Statistics Cache

Tracks performance metrics:

• Cache hits and misses
• Hit rate calculation
• Set and delete operations
• Thread-safe counters

2. TTL Cache

Automatic expiration:

• Time-based expiration
• Background cleanup goroutine
• Independent of HTTP cache headers
• Configurable TTL duration

Ideas for Other Custom Caches

• Size-limited cache: LRU eviction when size limit reached
• Compressed cache: See CompressCache for production implementation
• Encrypted cache: Encrypt sensitive data at rest
• Logging cache: Log all cache operations for debugging
• Circuit breaker cache: Fail fast on repeated errors
• Multi-level cache: L1 (memory) + L2 (disk/redis)
• Sharded cache: Distribute across multiple backends