Add prometheus metrics

Signed-off-by: Sylvain Rabot <sylvain@abstraction.fr>

cache.go

@@ -8,8 +8,105 @@ import (
 	"runtime"
 	"sync"
 	"time"
+
+	"github.com/prometheus/client_golang/prometheus"
 )
 
+var (
+	cacheItem = prometheus.NewGauge(
+		prometheus.GaugeOpts{
+			Namespace: "go",
+			Subsystem: "cache",
+			Name:      "set",
+			Help:      "Current number of cached items",
+		},
+	)
+
+	cacheAddTotal = prometheus.NewCounter(
+		prometheus.CounterOpts{
+			Namespace: "go",
+			Subsystem: "cache",
+			Name:      "add_total",
+			Help:      "Total number of add operations",
+		},
+	)
+
+	cacheDecrementTotal = prometheus.NewCounter(
+		prometheus.CounterOpts{
+			Namespace: "go",
+			Subsystem: "cache",
+			Name:      "decrement_total",
+			Help:      "Total number of decrement operations",
+		},
+	)
+
+	cacheDeleteTotal = prometheus.NewCounter(
+		prometheus.CounterOpts{
+			Namespace: "go",
+			Subsystem: "cache",
+			Name:      "delete_total",
+			Help:      "Total number of delete operations",
+		},
+	)
+
+	cacheFlushTotal = prometheus.NewCounter(
+		prometheus.CounterOpts{
+			Namespace: "go",
+			Subsystem: "cache",
+			Name:      "flush_total",
+			Help:      "Total number of flush operations",
+		},
+	)
+
+	cacheIncrementTotal = prometheus.NewCounter(
+		prometheus.CounterOpts{
+			Namespace: "go",
+			Subsystem: "cache",
+			Name:      "increment_total",
+			Help:      "Total number of increment operations",
+		},
+	)
+
+	cacheReplaceTotal = prometheus.NewCounter(
+		prometheus.CounterOpts{
+			Namespace: "go",
+			Subsystem: "cache",
+			Name:      "replace_total",
+			Help:      "Total number of replace operations",
+		},
+	)
+
+	cacheSetTotal = prometheus.NewCounter(
+		prometheus.CounterOpts{
+			Namespace: "go",
+			Subsystem: "cache",
+			Name:      "set_total",
+			Help:      "Total number of set operations",
+		},
+	)
+
+	cacheJanitorLastRun = prometheus.NewGauge(
+		prometheus.GaugeOpts{
+			Namespace: "go",
+			Subsystem: "cache",
+			Name:      "janitor_last_run",
+			Help:      "Timestamp of last janitor run",
+		},
+	)
+)
+
+func init() {
+	prometheus.MustRegister(cacheItem)
+	prometheus.MustRegister(cacheAddTotal)
+	prometheus.MustRegister(cacheDecrementTotal)
+	prometheus.MustRegister(cacheDeleteTotal)
+	prometheus.MustRegister(cacheFlushTotal)
+	prometheus.MustRegister(cacheIncrementTotal)
+	prometheus.MustRegister(cacheReplaceTotal)
+	prometheus.MustRegister(cacheSetTotal)
+	prometheus.MustRegister(cacheJanitorLastRun)
+}
+
 type Item struct {
 	Object     interface{}
 	Expiration int64
@@ -65,6 +162,8 @@ func (c *cache) Set(k string, x interface{}, d time.Duration) {
 	// TODO: Calls to mu.Unlock are currently not deferred because defer
 	// adds ~200 ns (as of go1.)
 	c.mu.Unlock()
+	cacheItem.Inc()
+	cacheSetTotal.Inc()
 }
 
 func (c *cache) set(k string, x interface{}, d time.Duration) {
@@ -91,13 +190,17 @@ func (c *cache) SetDefault(k string, x interface{}) {
 // key, or if the existing item has expired. Returns an error otherwise.
 func (c *cache) Add(k string, x interface{}, d time.Duration) error {
 	c.mu.Lock()
-	_, found := c.get(k)
+	ov, found := c.get(k)
 	if found {
 		c.mu.Unlock()
 		return fmt.Errorf("Item %s already exists", k)
 	}
 	c.set(k, x, d)
 	c.mu.Unlock()
+	if ov == nil {
+		cacheItem.Inc()
+	}
+	cacheAddTotal.Inc()
 	return nil
 }
 
@@ -112,6 +215,7 @@ func (c *cache) Replace(k string, x interface{}, d time.Duration) error {
 	}
 	c.set(k, x, d)
 	c.mu.Unlock()
+	cacheReplaceTotal.Inc()
 	return nil
 }
 
@@ -228,6 +332,7 @@ func (c *cache) Increment(k string, n int64) error {
 	}
 	c.items[k] = v
 	c.mu.Unlock()
+	cacheIncrementTotal.Inc()
 	return nil
 }
 
@@ -254,6 +359,7 @@ func (c *cache) IncrementFloat(k string, n float64) error {
 	}
 	c.items[k] = v
 	c.mu.Unlock()
+	cacheIncrementTotal.Inc()
 	return nil
 }
 
@@ -276,6 +382,7 @@ func (c *cache) IncrementInt(k string, n int) (int, error) {
 	v.Object = nv
 	c.items[k] = v
 	c.mu.Unlock()
+	cacheIncrementTotal.Inc()
 	return nv, nil
 }
 
@@ -298,6 +405,7 @@ func (c *cache) IncrementInt8(k string, n int8) (int8, error) {
 	v.Object = nv
 	c.items[k] = v
 	c.mu.Unlock()
+	cacheIncrementTotal.Inc()
 	return nv, nil
 }
 
@@ -320,6 +428,7 @@ func (c *cache) IncrementInt16(k string, n int16) (int16, error) {
 	v.Object = nv
 	c.items[k] = v
 	c.mu.Unlock()
+	cacheIncrementTotal.Inc()
 	return nv, nil
 }
 
@@ -342,6 +451,7 @@ func (c *cache) IncrementInt32(k string, n int32) (int32, error) {
 	v.Object = nv
 	c.items[k] = v
 	c.mu.Unlock()
+	cacheIncrementTotal.Inc()
 	return nv, nil
 }
 
@@ -364,6 +474,7 @@ func (c *cache) IncrementInt64(k string, n int64) (int64, error) {
 	v.Object = nv
 	c.items[k] = v
 	c.mu.Unlock()
+	cacheIncrementTotal.Inc()
 	return nv, nil
 }
 
@@ -386,6 +497,7 @@ func (c *cache) IncrementUint(k string, n uint) (uint, error) {
 	v.Object = nv
 	c.items[k] = v
 	c.mu.Unlock()
+	cacheIncrementTotal.Inc()
 	return nv, nil
 }
 
@@ -408,6 +520,7 @@ func (c *cache) IncrementUintptr(k string, n uintptr) (uintptr, error) {
 	v.Object = nv
 	c.items[k] = v
 	c.mu.Unlock()
+	cacheIncrementTotal.Inc()
 	return nv, nil
 }
 
@@ -430,6 +543,7 @@ func (c *cache) IncrementUint8(k string, n uint8) (uint8, error) {
 	v.Object = nv
 	c.items[k] = v
 	c.mu.Unlock()
+	cacheIncrementTotal.Inc()
 	return nv, nil
 }
 
@@ -452,6 +566,7 @@ func (c *cache) IncrementUint16(k string, n uint16) (uint16, error) {
 	v.Object = nv
 	c.items[k] = v
 	c.mu.Unlock()
+	cacheIncrementTotal.Inc()
 	return nv, nil
 }
 
@@ -474,6 +589,7 @@ func (c *cache) IncrementUint32(k string, n uint32) (uint32, error) {
 	v.Object = nv
 	c.items[k] = v
 	c.mu.Unlock()
+	cacheIncrementTotal.Inc()
 	return nv, nil
 }
 
@@ -496,6 +612,7 @@ func (c *cache) IncrementUint64(k string, n uint64) (uint64, error) {
 	v.Object = nv
 	c.items[k] = v
 	c.mu.Unlock()
+	cacheIncrementTotal.Inc()
 	return nv, nil
 }
 
@@ -518,6 +635,7 @@ func (c *cache) IncrementFloat32(k string, n float32) (float32, error) {
 	v.Object = nv
 	c.items[k] = v
 	c.mu.Unlock()
+	cacheIncrementTotal.Inc()
 	return nv, nil
 }
 
@@ -540,6 +658,7 @@ func (c *cache) IncrementFloat64(k string, n float64) (float64, error) {
 	v.Object = nv
 	c.items[k] = v
 	c.mu.Unlock()
+	cacheIncrementTotal.Inc()
 	return nv, nil
 }
 
@@ -590,6 +709,7 @@ func (c *cache) Decrement(k string, n int64) error {
 	}
 	c.items[k] = v
 	c.mu.Unlock()
+	cacheDecrementTotal.Inc()
 	return nil
 }
 
@@ -616,6 +736,7 @@ func (c *cache) DecrementFloat(k string, n float64) error {
 	}
 	c.items[k] = v
 	c.mu.Unlock()
+	cacheDecrementTotal.Inc()
 	return nil
 }
 
@@ -638,6 +759,7 @@ func (c *cache) DecrementInt(k string, n int) (int, error) {
 	v.Object = nv
 	c.items[k] = v
 	c.mu.Unlock()
+	cacheDecrementTotal.Inc()
 	return nv, nil
 }
 
@@ -660,6 +782,7 @@ func (c *cache) DecrementInt8(k string, n int8) (int8, error) {
 	v.Object = nv
 	c.items[k] = v
 	c.mu.Unlock()
+	cacheDecrementTotal.Inc()
 	return nv, nil
 }
 
@@ -682,6 +805,7 @@ func (c *cache) DecrementInt16(k string, n int16) (int16, error) {
 	v.Object = nv
 	c.items[k] = v
 	c.mu.Unlock()
+	cacheDecrementTotal.Inc()
 	return nv, nil
 }
 
@@ -704,6 +828,7 @@ func (c *cache) DecrementInt32(k string, n int32) (int32, error) {
 	v.Object = nv
 	c.items[k] = v
 	c.mu.Unlock()
+	cacheDecrementTotal.Inc()
 	return nv, nil
 }
 
@@ -726,6 +851,7 @@ func (c *cache) DecrementInt64(k string, n int64) (int64, error) {
 	v.Object = nv
 	c.items[k] = v
 	c.mu.Unlock()
+	cacheDecrementTotal.Inc()
 	return nv, nil
 }
 
@@ -748,6 +874,7 @@ func (c *cache) DecrementUint(k string, n uint) (uint, error) {
 	v.Object = nv
 	c.items[k] = v
 	c.mu.Unlock()
+	cacheDecrementTotal.Inc()
 	return nv, nil
 }
 
@@ -770,6 +897,7 @@ func (c *cache) DecrementUintptr(k string, n uintptr) (uintptr, error) {
 	v.Object = nv
 	c.items[k] = v
 	c.mu.Unlock()
+	cacheDecrementTotal.Inc()
 	return nv, nil
 }
 
@@ -792,6 +920,7 @@ func (c *cache) DecrementUint8(k string, n uint8) (uint8, error) {
 	v.Object = nv
 	c.items[k] = v
 	c.mu.Unlock()
+	cacheDecrementTotal.Inc()
 	return nv, nil
 }
 
@@ -814,6 +943,7 @@ func (c *cache) DecrementUint16(k string, n uint16) (uint16, error) {
 	v.Object = nv
 	c.items[k] = v
 	c.mu.Unlock()
+	cacheDecrementTotal.Inc()
 	return nv, nil
 }
 
@@ -836,6 +966,7 @@ func (c *cache) DecrementUint32(k string, n uint32) (uint32, error) {
 	v.Object = nv
 	c.items[k] = v
 	c.mu.Unlock()
+	cacheDecrementTotal.Inc()
 	return nv, nil
 }
 
@@ -858,6 +989,7 @@ func (c *cache) DecrementUint64(k string, n uint64) (uint64, error) {
 	v.Object = nv
 	c.items[k] = v
 	c.mu.Unlock()
+	cacheDecrementTotal.Inc()
 	return nv, nil
 }
 
@@ -880,6 +1012,7 @@ func (c *cache) DecrementFloat32(k string, n float32) (float32, error) {
 	v.Object = nv
 	c.items[k] = v
 	c.mu.Unlock()
+	cacheDecrementTotal.Inc()
 	return nv, nil
 }
 
@@ -902,6 +1035,7 @@ func (c *cache) DecrementFloat64(k string, n float64) (float64, error) {
 	v.Object = nv
 	c.items[k] = v
 	c.mu.Unlock()
+	cacheDecrementTotal.Inc()
 	return nv, nil
 }
 
@@ -916,13 +1050,15 @@ func (c *cache) Delete(k string) {
 }
 
 func (c *cache) delete(k string) (interface{}, bool) {
-	var ret interface{} = nil
 	var found = false
+	var ret interface{}
 
 	if v, ok := c.items[k]; ok {
 		found = true
 		ret = v.Object
 		delete(c.items, k)
+		cacheItem.Dec()
+		cacheDeleteTotal.Inc()
 	}
 
 	return ret, found
@@ -1013,9 +1149,13 @@ func (c *cache) Load(r io.Reader) error {
 		c.mu.Lock()
 		defer c.mu.Unlock()
 		for k, v := range items {
-			ov, found := c.items[k]
-			if !found || ov.Expired() {
+			ov, found := c.get(k)
+			if !found {
 				c.items[k] = v
+
+				if ov == nil {
+					cacheItem.Inc()
+				}
 			}
 		}
 	}
@@ -1070,8 +1210,10 @@ func (c *cache) ItemCount() int {
 // Delete all items from the cache.
 func (c *cache) Flush() {
 	c.mu.Lock()
+	cacheItem.Sub(float64(len(c.items)))
 	c.items = map[string]Item{}
 	c.mu.Unlock()
+	cacheFlushTotal.Inc()
 }
 
 type janitor struct {
@@ -1084,6 +1226,7 @@ func (j *janitor) Run(c *cache) {
 	for {
 		select {
 		case <-ticker.C:
+			cacheJanitorLastRun.Set(float64(time.Now().Unix()))
 			c.DeleteExpired()
 		case <-j.stop:
 			ticker.Stop()
@@ -1113,6 +1256,7 @@ func newCache(de time.Duration, m map[string]Item) *cache {
 		defaultExpiration: de,
 		items:             m,
 	}
+	cacheItem.Add(float64(len(m)))
 	return c
 }
 

cache_test.go

@@ -3,13 +3,21 @@ package cache
 import (
 	"bytes"
 	"io/ioutil"
+	"net/http"
 	"runtime"
 	"strconv"
 	"sync"
 	"testing"
 	"time"
+
+	"github.com/prometheus/client_golang/prometheus/promhttp"
 )
 
+func init() {
+	http.Handle("/metrics", promhttp.Handler())
+	go http.ListenAndServe("localhost:9000", nil)
+}
+
 type TestStruct struct {
 	Num      int
 	Children []*TestStruct