hit/miss stats for matchcache

mdata/init.go

@@ -91,6 +91,6 @@ func ConfigProcess() {
 }
 
 func Cache(cleanInterval, expireAfter time.Duration) {
-	schemasCache = matchcache.New(cleanInterval, expireAfter)
-	aggsCache = matchcache.New(cleanInterval, expireAfter)
+	schemasCache = matchcache.New("schemas", cleanInterval, expireAfter)
+	aggsCache = matchcache.New("aggs", cleanInterval, expireAfter)
 }

mdata/matchcache/matchcache.go

@@ -1,8 +1,11 @@
 package matchcache
 
 import (
+	"fmt"
 	"sync"
 	"time"
+
+	"github.com/raintank/metrictank/stats"
 )
 
 // Cache caches key to uint16 lookups (for schemas and aggregations)
@@ -15,18 +18,22 @@ type Cache struct {
 
 	cleanInterval time.Duration
 	expireAfter   time.Duration
+	hits          *stats.Counter32
+	miss          *stats.Counter32
 }
 
 type Item struct {
 	val  uint16
 	seen int64
 }
 
-func New(cleanInterval, expireAfter time.Duration) *Cache {
+func New(name string, cleanInterval, expireAfter time.Duration) *Cache {
 	m := &Cache{
 		data:          make(map[string]Item),
 		cleanInterval: cleanInterval,
 		expireAfter:   expireAfter,
+		hits:          stats.NewCounter32(fmt.Sprintf("idx.matchcache.%s.ops.hit", name)),
+		miss:          stats.NewCounter32(fmt.Sprintf("idx.matchcache.%s.ops.miss", name)),
 	}
 	go m.maintain()
 	return m
@@ -38,7 +45,10 @@ type AddFunc func(key string) uint16
 func (m *Cache) Get(key string, fn AddFunc) uint16 {
 	m.Lock()
 	item, ok := m.data[key]
-	if !ok {
+	if ok {
+		m.hits.Inc()
+	} else {
+		m.miss.Inc()
 		item.val = fn(key)
 	}
 	item.seen = time.Now().Unix()