Cache

A thread-safe, type-safe generic cache for Go with zero dependencies.

Features

• 🔒 Thread-safe: Safe for concurrent access with efficient read/write locking
• 🎯 Type-safe: Leverages Go generics for compile-time type safety
• 🚀 Zero dependencies: Only uses Go standard library (tests use testify)
• ⚡ Efficient: Double-check locking pattern minimizes lock contention
• 🔄 Smart error handling: Errors are not cached, allowing retries
• 🗂️ Type partitioning: Separate cache spaces per type automatically

Requirements

• Go 1.18 or later

Installation

go get github.com/alexanderbotero/cache

Quick Start

package main

import (
    "fmt"
    "log"
    
    "github.com/alexanderbotero/cache"
)

func main() {
    // Cache a simple value
    result, err := cache.Get(1, func(id int) (string, error) {
        // This function is only called once per unique key
        return fmt.Sprintf("user-%d", id), nil
    })
    if err != nil {
        log.Fatal(err)
    }
    fmt.Println(result) // Output: user-1
    
    // Subsequent calls return the cached value instantly
    result2, _ := cache.Get(1, func(id int) (string, error) {
        return "this won't be called", nil
    })
    fmt.Println(result2) // Output: user-1
}

Usage Examples

Basic Caching

// Cache database queries
user, err := cache.Get(userID, func(id int) (*User, error) {
    return db.GetUser(id)
})

Different Types, Separate Caches

// String cache
str, _ := cache.Get(1, func(k int) (string, error) {
    return "hello", nil
})

// Int cache with same key - completely separate!
num, _ := cache.Get(1, func(k int) (int, error) {
    return 42, nil
})

Error Handling

// Errors are NOT cached - retries are allowed
result, err := cache.Get("key", func(k string) (string, error) {
    if networkIsDown() {
        return "", errors.New("network error") // Not cached
    }
    return "success", nil // This will be cached
})

Pointer Types and Interfaces

// Works with pointers
user, err := cache.Get(1, func(id int) (*User, error) {
    return &User{ID: id, Name: "Alice"}, nil
})

// Works with interfaces
reader, err := cache.Get("file.txt", func(path string) (io.Reader, error) {
    return os.Open(path)
})

How It Works

1. Type Partitioning: The cache automatically separates data by type using reflect.Type as a key. This means Get[int, string] and Get[int, int] maintain separate cache spaces.

2. Thread Safety: Uses sync.RWMutex for efficient concurrent access:

   • Multiple goroutines can read simultaneously
   • Writes are exclusive
   • Double-check locking prevents unnecessary writes

3. Getter Function: The getterFunc is called only once per unique key (unless it returns an error). Subsequent calls return the cached value.

API

Cache

func Get[K comparable, V any](key K, getterFunc func(K) (V, error)) (V, error)

Retrieves a value from cache or computes it using getterFunc.

Parameters:

• key: The cache key (must be comparable)
• getterFunc: Function to generate the value if not cached (cannot be nil)

Returns:

• The cached or computed value
• An error if:
  • getterFunc is nil
  • getterFunc returns an error
  • Cache corruption is detected (internal bug)

Thread-Safety: This function is safe for concurrent use.

Limitations

• No built-in eviction policy (cache grows indefinitely)
• No TTL (time-to-live) support
• No memory limits
• Global cache instance (all callers share the same cache)

License

This project is licensed under the MIT License - see the LICENSE file for details.

Author

Alexander Botero (@alexanderbotero)