GCache

Cache library for golang. It supports expirable Cache, LFU, LRU and ARC.

Features

Supports expirable Cache, LFU, LRU and ARC.
Goroutine safe.
Supports event handlers which evict and add entry. (Optional)
Automatically load cache if it doesn't exists. (Optional)

Install

$ go get github.com/bluele/gcache

Example

Manually set a key-value pair.

package main

import (
  "github.com/bluele/gcache"
  "fmt"
)

func main() {
  gc := gcache.New(20).
    LRU().
    Build()
  gc.Set("key", "ok")
  value, err := gc.Get("key")
  if err != nil {
    panic(err)
  }
  fmt.Println("Get:", value)
}

Get: ok

Automatically load value

package main

import (
  "github.com/bluele/gcache"
  "fmt"
)

func main() {
  gc := gcache.New(20).
    LRU().
    LoaderFunc(func(key interface{}) (interface{}, error) {
      return "ok", nil
    }).
    Build()
  value, err := gc.Get("key")
  if err != nil {
    panic(err)
  }
  fmt.Println("Get:", value)
}

Get: ok

Cache Algorithm

Least-Frequently Used (LFU)

Discards the least frequently used items first.

func main() {
  // size: 10
  gc := gcache.New(10).
    LFU().
    Build()
  gc.Set("key", "value")
}

Least Recently Used (LRU)

Discards the least recently used items first.

func main() {
  // size: 10
  gc := gcache.New(10).
    LRU().
    Build()
  gc.Set("key", "value")
}

Adaptive Replacement Cache (ARC)

Constantly balances between LRU and LFU, to improve the combined result.

detail: http://en.wikipedia.org/wiki/Adaptive_replacement_cache

func main() {
  // size: 10
  gc := gcache.New(10).
    ARC().
    Build()
  gc.Set("key", "value")
}

SimpleCache (Default)

SimpleCache has no clear priority for evict cache. It depends on key-value map order.

func main() {
  // size: 10
  gc := gcache.New(10).Build()
  gc.Set("key", "value")
  v, err := gc.Get("key")
  if err != nil {
    panic(err)
  }
}

Loading Cache

If specified LoaderFunc, values are automatically loaded by the cache, and are stored in the cache until either evicted or manually invalidated.

func main() {
  gc := gcache.New(10).
    LRU().
    LoaderFunc(func(key interface{}) (interface{}, error) {
      return "value", nil
    }).
    Build()
  v, _ := gc.Get("key")
  // output: "value"
  fmt.Println(v)
}

GCache coordinates cache fills such that only one load in one process of an entire replicated set of processes populates the cache, then multiplexes the loaded value to all callers.

Expirable cache

func main() {
  // LRU cache, size: 10, expiration: after a hour
  gc := gcache.New(10).
    LRU().
    Expiration(time.Hour).
    Build()
}

Event handlers

Evicted handler

Event handler for evict the entry.

func main() {
  gc := gcache.New(2).
    EvictedFunc(func(key, value interface{}) {
      fmt.Println("evicted key:", key)
    }).
    Build()
  for i := 0; i < 3; i++ {
    gc.Set(i, i*i)
  }
}

evicted key: 0

Added handler

Event handler for add the entry.

func main() {
  gc := gcache.New(2).
    AddedFunc(func(key, value interface{}) {
      fmt.Println("added key:", key)
    }).
    Build()
  for i := 0; i < 3; i++ {
    gc.Set(i, i*i)
  }
}

added key: 0
added key: 1
added key: 2

Author

Jun Kimura

tysyzp / gcache