Use groupcache for LRU cache

Signed-off-by: Brian Akins <205350+bakins@users.noreply.github.com>

go.mod

@@ -2,7 +2,7 @@ module github.com/prometheus/statsd_exporter
 
 require (
 	github.com/go-kit/kit v0.10.0
-	github.com/hashicorp/golang-lru v0.5.4
+	github.com/golang/groupcache v0.0.0-20210331224755-41bb18bfe9da
 	github.com/prometheus/client_golang v1.9.0
 	github.com/prometheus/client_model v0.2.0
 	github.com/prometheus/common v0.19.0

go.sum

@@ -76,6 +76,8 @@ github.com/gogo/protobuf v1.2.1/go.mod h1:hp+jE20tsWTFYpLwKvXlhS1hjn+gTNwPg2I6zV
 github.com/golang/glog v0.0.0-20160126235308-23def4e6c14b/go.mod h1:SBH7ygxi8pfUlaOkMMuAQtPIUF8ecWP5IEl/CR7VP2Q=
 github.com/golang/groupcache v0.0.0-20160516000752-02826c3e7903/go.mod h1:cIg4eruTrX1D+g88fzRXU5OdNfaM+9IcxsU14FzY7Hc=
 github.com/golang/groupcache v0.0.0-20190702054246-869f871628b6/go.mod h1:cIg4eruTrX1D+g88fzRXU5OdNfaM+9IcxsU14FzY7Hc=
+github.com/golang/groupcache v0.0.0-20210331224755-41bb18bfe9da h1:oI5xCqsCo564l8iNU+DwB5epxmsaqB+rhGL0m5jtYqE=
+github.com/golang/groupcache v0.0.0-20210331224755-41bb18bfe9da/go.mod h1:cIg4eruTrX1D+g88fzRXU5OdNfaM+9IcxsU14FzY7Hc=
 github.com/golang/mock v1.1.1/go.mod h1:oTYuIxOrZwtPieC+H1uAHpcLFnEyAGVDL/k47Jfbm0A=
 github.com/golang/protobuf v1.2.0/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
 github.com/golang/protobuf v1.3.1/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
@@ -123,8 +125,6 @@ github.com/hashicorp/go-version v1.2.0/go.mod h1:fltr4n8CU8Ke44wwGCBoEymUuxUHl09
 github.com/hashicorp/go.net v0.0.1/go.mod h1:hjKkEWcCURg++eb33jQU7oqQcI9XDCnUzHA0oac0k90=
 github.com/hashicorp/golang-lru v0.5.0/go.mod h1:/m3WP610KZHVQ1SGc6re/UDhFvYD7pJ4Ao+sR/qLZy8=
 github.com/hashicorp/golang-lru v0.5.1/go.mod h1:/m3WP610KZHVQ1SGc6re/UDhFvYD7pJ4Ao+sR/qLZy8=
-github.com/hashicorp/golang-lru v0.5.4 h1:YDjusn29QI/Das2iO9M0BHnIbxPeyuCHsjMW+lJfyTc=
-github.com/hashicorp/golang-lru v0.5.4/go.mod h1:iADmTwqILo4mZ8BN3D2Q6+9jd8WM5uGBxy+E8yxSoD4=
 github.com/hashicorp/logutils v1.0.0/go.mod h1:QIAnNjmIWmVIIkWDTG1z5v++HQmx9WQRO+LraFDTW64=
 github.com/hashicorp/mdns v1.0.0/go.mod h1:tL+uN++7HEJ6SQLQ2/p+z2pH24WQKWjBPkE0mNTz8vQ=
 github.com/hashicorp/memberlist v0.1.3/go.mod h1:ajVTdAv/9Im8oMAAj5G31PhhMCZJV2pPBoIllUwCN7I=

pkg/mappercache/lru/lru.go

@@ -14,15 +14,17 @@
 package lru
 
 import (
+	"sync"
+
 	"github.com/prometheus/client_golang/prometheus"
 
-	lru2 "github.com/hashicorp/golang-lru"
+	"github.com/golang/groupcache/lru"
 
 	"github.com/prometheus/statsd_exporter/pkg/mappercache"
 )
 
 type metricMapperLRUCache struct {
-	cache   *lru2.Cache
+	cache   *lruCache
 	metrics *mappercache.CacheMetrics
 }
 
@@ -32,10 +34,7 @@ func NewMetricMapperLRUCache(reg prometheus.Registerer, size int) (*metricMapper
 	}
 
 	metrics := mappercache.NewCacheMetrics(reg)
-	cache, err := lru2.New(size)
+	cache := newLruCache(size)
-	if err != nil {
-		return &metricMapperLRUCache{}, err
-	}
 
 	return &metricMapperLRUCache{metrics: metrics, cache: cache}, nil
 }
@@ -60,6 +59,45 @@ func (m *metricMapperLRUCache) trackCacheLength() {
 }
 
 func (m *metricMapperLRUCache) Reset() {
-	m.cache.Purge()
+	m.cache.Clear()
 	m.metrics.CacheLength.Set(0)
 }
+
+type lruCache struct {
+	cache *lru.Cache
+	lock  sync.RWMutex
+}
+
+func newLruCache(maxEntries int) *lruCache {
+	return &lruCache{
+		cache: lru.New(maxEntries),
+	}
+}
+
+func (l *lruCache) Get(key string) (interface{}, bool) {
+	l.lock.RLock()
+	defer l.lock.RUnlock()
+
+	return l.cache.Get(key)
+}
+
+func (l *lruCache) Add(key string, value interface{}) {
+	l.lock.Lock()
+	defer l.lock.Unlock()
+
+	l.cache.Add(key, value)
+}
+
+func (l *lruCache) Len() int {
+	l.lock.RLock()
+	defer l.lock.RUnlock()
+
+	return l.cache.Len()
+}
+
+func (l *lruCache) Clear() {
+	l.lock.Lock()
+	defer l.lock.Unlock()
+
+	l.cache.Clear()
+}