loader

README

cache-loader

Golang Cache Loader

Feature

• Thread safe
• Fetch once even when concurrent process request same key.
• stale-while-revalidate when item is expired

Example

func main() {
  itemLoader := loader.NewLRU(fetchItem, 5 * time.Minute, 1000)
  item, err := loader.Get("key")
  // use item
}

func fetchItem(key interface{}) (interface{}, error) {
  res, err := http.Get("https://example.com/item/" + key)
  if err != nil {
    return nil, err
  }
  return processResponse(res)
}

Documentation

Index

• type Cache
  • func InMemoryCache() Cache
• type LRUCache
  • func (c *LRUCache) Add(key, value interface{})
  • func (c *LRUCache) Remove(key interface{})
• type LoadFunc
• type Loader
  • func New(fn LoadFunc, ttl time.Duration, cache Cache) *Loader
  • func NewLRU(fn LoadFunc, ttl time.Duration, size int) *Loader
  • func (l *Loader) Get(key interface{}) (interface{}, error)

Types

type Cache

type Cache interface {
	Add(key, value interface{})
	Get(key interface{}) (value interface{}, ok bool)
	Remove(key interface{})
}

Cache stores the items you can use ARCCache or TwoQueueCache from github.com/hashicorp/golang-lru

func InMemoryCache

func InMemoryCache() Cache

type LRUCache

type LRUCache struct {
	*lru.Cache
}

LRUCache wraps hashicorp's lru cache object, so it's compatible with loader cache

func (*LRUCache) Add

func (c *LRUCache) Add(key, value interface{})

Add item to cache

func (*LRUCache) Remove

func (c *LRUCache) Remove(key interface{})

Remove item from cache

type LoadFunc

type LoadFunc func(key interface{}) (interface{}, error)

LoadFunc loads the value based on key

type Loader

type Loader struct {
	// contains filtered or unexported fields
}

Loader manage items in cache and fetch them if not exist

func New

func New(fn LoadFunc, ttl time.Duration, cache Cache) *Loader

New creates new Loader

func NewLRU

func NewLRU(fn LoadFunc, ttl time.Duration, size int) *Loader

NewLRU creates Loader with lru based cache

func (*Loader) Get

func (l *Loader) Get(key interface{}) (interface{}, error)

Get the item. If it doesn't exist on cache, Loader will call LoadFunc once even when other go routine access the same key. If the item is expired, it will return old value while loading new one.