expirable-cache¶
Package cache implements expirable cache.
- Support LRC, LRU and TTL-based eviction.
- Package is thread-safe and doesn’t spawn any goroutines.
- On every Set() call, cache deletes single oldest entry in case it’s expired.
- In case MaxSize is set, cache deletes the oldest entry disregarding its expiration date to maintain the size, either using LRC or LRU eviction.
- In case of default TTL (10 years) and default MaxSize (0, unlimited) the cache will be truly unlimited and will never delete entries from itself automatically.
Important: only reliable way of not having expired entries stuck in a cache is to run cache.DeleteExpired periodically using time.Ticker, advisable period is ½ of TTL.
This cache is heavily inspired by hashicorp/golang-lru simplelru implementation. v3 implements simplelru.LRUCache interface, so if you use a subset of functions, so you can switch from github.com/hashicorp/golang-lru/v2/simplelru or github.com/hashicorp/golang-lru/v2/expirable without any changes in your code except for cache creation. Key differences are:
- Support LRC (Least Recently Created) in addition to LRU and TTL-based eviction
- Supports per-key TTL setting
- Doesn’t spawn any goroutines, whereas
hashicorp/golang-lru/v2/expirablespawns goroutine which is never killed (as of now) - Provides stats about hits and misses, added and evicted entries
Usage example¶
package main
import (
"fmt"
"time"
"github.com/go-pkgz/expirable-cache/v3"
)
func main() {
// make cache with short TTL and 3 max keys
c := cache.NewCache[string, string]().WithMaxKeys(3).WithTTL(time.Millisecond * 10)
// set value under key1.
// with 0 ttl (last parameter) will use cache-wide setting instead (10ms).
c.Set("key1", "val1", 0)
// get value under key1
r, ok := c.Get("key1")
// check for OK value, because otherwise return would be nil and
// type conversion will panic
if ok {
rstr := r.(string) // convert cached value from interface{} to real type
fmt.Printf("value before expiration is found: %v, value: %v\n", ok, rstr)
}
time.Sleep(time.Millisecond * 11)
// get value under key1 after key expiration
r, ok = c.Get("key1")
// don't convert to string as with ok == false value would be nil
fmt.Printf("value after expiration is found: %v, value: %v\n", ok, r)
// set value under key2, would evict old entry because it is already expired.
// ttl (last parameter) overrides cache-wide ttl.
c.Set("key2", "val2", time.Minute*5)
fmt.Printf("%+v\n", c)
// Output:
// value before expiration is found: true, value: val1
// value after expiration is found: false, value: <nil>
// Size: 1, Stats: {Hits:1 Misses:1 Added:2 Evicted:1} (50.0%)
}
v3 performance improvements¶
v3 (and v2) are done using generics and 38-42% faster than v1 without them according to benchmarks.
v1
~/expirable-cache ❯ go test -bench=.
goos: darwin
goarch: arm64
pkg: github.com/go-pkgz/expirable-cache
BenchmarkLRU_Rand_NoExpire-8 4494738 272.4 ns/op
--- BENCH: BenchmarkLRU_Rand_NoExpire-8
cache_test.go:46: hit: 0 miss: 1 ratio: 0.000000
cache_test.go:46: hit: 1 miss: 99 ratio: 0.010000
cache_test.go:46: hit: 1352 miss: 8648 ratio: 0.135200
cache_test.go:46: hit: 248678 miss: 751322 ratio: 0.248678
cache_test.go:46: hit: 1121791 miss: 3372947 ratio: 0.249579
BenchmarkLRU_Freq_NoExpire-8 4612648 261.6 ns/op
--- BENCH: BenchmarkLRU_Freq_NoExpire-8
cache_test.go:74: hit: 1 miss: 0 ratio: 1.000000
cache_test.go:74: hit: 100 miss: 0 ratio: 1.000000
cache_test.go:74: hit: 9825 miss: 175 ratio: 0.982500
cache_test.go:74: hit: 312345 miss: 687655 ratio: 0.312345
cache_test.go:74: hit: 1414620 miss: 3198028 ratio: 0.306683
BenchmarkLRU_Rand_WithExpire-8 4109704 286.5 ns/op
--- BENCH: BenchmarkLRU_Rand_WithExpire-8
cache_test.go:99: hit: 0 miss: 1 ratio: 0.000000
cache_test.go:99: hit: 0 miss: 100 ratio: 0.000000
cache_test.go:99: hit: 1304 miss: 8696 ratio: 0.130400
cache_test.go:99: hit: 248310 miss: 751690 ratio: 0.248310
cache_test.go:99: hit: 1027317 miss: 3082387 ratio: 0.249973
BenchmarkLRU_Freq_WithExpire-8 4341217 279.6 ns/op
--- BENCH: BenchmarkLRU_Freq_WithExpire-8
cache_test.go:127: hit: 1 miss: 0 ratio: 1.000000
cache_test.go:127: hit: 100 miss: 0 ratio: 1.000000
cache_test.go:127: hit: 9868 miss: 132 ratio: 0.986800
cache_test.go:127: hit: 38221 miss: 961779 ratio: 0.038221
cache_test.go:127: hit: 37296 miss: 4303921 ratio: 0.008591
PASS
ok github.com/go-pkgz/expirable-cache 18.307s
v3
~/Desktop/expirable-cache/v3 master !2 ❯ go test -bench=.
goos: darwin
goarch: arm64
pkg: github.com/go-pkgz/expirable-cache/v3
BenchmarkLRU_Rand_NoExpire-8 7556680 158.1 ns/op
--- BENCH: BenchmarkLRU_Rand_NoExpire-8
cache_test.go:47: hit: 0 miss: 1 ratio: 0.000000
cache_test.go:47: hit: 0 miss: 100 ratio: 0.000000
cache_test.go:47: hit: 1409 miss: 8591 ratio: 0.140900
cache_test.go:47: hit: 249063 miss: 750937 ratio: 0.249063
cache_test.go:47: hit: 1887563 miss: 5669117 ratio: 0.249787
BenchmarkLRU_Freq_NoExpire-8 7876738 150.9 ns/op
--- BENCH: BenchmarkLRU_Freq_NoExpire-8
cache_test.go:75: hit: 1 miss: 0 ratio: 1.000000
cache_test.go:75: hit: 100 miss: 0 ratio: 1.000000
cache_test.go:75: hit: 9850 miss: 150 ratio: 0.985000
cache_test.go:75: hit: 310888 miss: 689112 ratio: 0.310888
cache_test.go:75: hit: 2413312 miss: 5463426 ratio: 0.306385
BenchmarkLRU_Rand_WithExpire-8 6822362 175.3 ns/op
--- BENCH: BenchmarkLRU_Rand_WithExpire-8
cache_test.go:100: hit: 0 miss: 1 ratio: 0.000000
cache_test.go:100: hit: 0 miss: 100 ratio: 0.000000
cache_test.go:100: hit: 1326 miss: 8674 ratio: 0.132600
cache_test.go:100: hit: 248508 miss: 751492 ratio: 0.248508
cache_test.go:100: hit: 1704172 miss: 5118190 ratio: 0.249792
BenchmarkLRU_Freq_WithExpire-8 7098261 168.1 ns/op
--- BENCH: BenchmarkLRU_Freq_WithExpire-8
cache_test.go:128: hit: 1 miss: 0 ratio: 1.000000
cache_test.go:128: hit: 100 miss: 0 ratio: 1.000000
cache_test.go:128: hit: 9842 miss: 158 ratio: 0.984200
cache_test.go:128: hit: 90167 miss: 909833 ratio: 0.090167
cache_test.go:128: hit: 90421 miss: 7007840 ratio: 0.012738
PASS
ok github.com/go-pkgz/expirable-cache/v3 24.315s