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, purge, 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
Manually set a key-value pair, with an expiration time.
package main
import (
"github.com/bluele/gcache"
"fmt"
"time"
)
func main() {
gc := gcache.New(20).
LRU().
Build()
gc.SetWithExpire("key", "ok", time.Second*10)
value, _ := gc.Get("key")
fmt.Println("Get:", value)
// Wait for value to expire
time.Sleep(time.Second*10)
value, err = gc.Get("key")
if err != nil {
panic(err)
}
fmt.Println("Get:", value)
}
Get: ok
// 10 seconds later, new attempt:
panic: ErrKeyNotFound
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
Automatically load value with expiration
package main
import (
"fmt"
"time"
"github.com/bluele/gcache"
)
func main() {
var evictCounter, loaderCounter, purgeCounter int
gc := gcache.New(20).
LRU().
LoaderExpireFunc(func(key interface{}) (interface{}, *time.Duration, error) {
loaderCounter++
expire := 1 * time.Second
return "ok", &expire, nil
}).
EvictedFunc(func(key, value interface{}) {
evictCounter++
fmt.Println("evicted key:", key)
}).
PurgeVisitorFunc(func(key, value interface{}) {
purgeCounter++
fmt.Println("purged key:", key)
}).
Build()
value, err := gc.Get("key")
if err != nil {
panic(err)
}
fmt.Println("Get:", value)
time.Sleep(1 * time.Second)
value, err = gc.Get("key")
if err != nil {
panic(err)
}
fmt.Println("Get:", value)
gc.Purge()
if loaderCounter != evictCounter+purgeCounter {
panic("bad")
}
}
Get: ok
evicted key: key
Get: ok
purged key: key
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