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LRUCache

A map + linked-list backed LRU cache. Cached items belong to a primary and secondary cache key. This allows you to generate multiple versions of the same object yet purge all variations. For example:

// 100MB
cache := lrucache.New(lrucache.Configure())
cache.Set("video/43", ".json", video1)
cache.Set("video/43", ".xml", video2)

// will remove both entries from the cache
cache.Remove("video/43")

The cache takes some liberties. For example, a delay prevents recently promoted items from being re-promoted (thus minimizing the occurrences of a global write lock on the linked list). Furthermore, the garbage collection keeps some artifacts around. We've found these compromises suitable for caching HTTP responses.

There are now a number of respectable caching libraries for Go, such as GroupCache and Vitess.

The cache is thread-safe.

Usage

Start by creating an instance of the cache:

cache := lrucache.New(lrucache.Configure())

The cache size, itemsToPrune and callback can be specific via the configuration object:

cache := lrucache.New(
      lrucache.Configure()
        .Size(1 * 1024 * 1024 * 1024)  //1GB
        .ItemsToPrune(5000)            //# of items to prune when a GC runs
        .Callback(func(){ atomic.AddUint64(&gcs, 1) }) //called whenever a GC runs
    )

After creating an instance, you can Get, Set or Remove. Items added to the cache must implement the lrucache.CacheItem interface, which simply defines Debug() []byte and Expiry() time.Time:

type Response struct {
  body []byte
  statusCode int
}
func (r *Response) Debug() []byte {
  // Adds arbitrary data to the output of cache.Debug() for this line item.
  // In this case, returning len(body) might be useful, or just do nothing
  // if you aren't using Debug
  return []byte{}
}
func (r *Response) Expires() time.Time {
  return time.Now().Add(time.Hour)
}

Installation

Install using the "go get" command:

go get github.com/viki-org/lrucache

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