add more metrics

grain-pool.go

@@ -5,6 +5,20 @@ import (
 	"fmt"
 	"log"
 	"time"
+
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promauto"
+)
+
+var (
+	poolGrains = promauto.NewGauge(prometheus.GaugeOpts{
+		Name: "cart_grains_in_pool",
+		Help: "The total number of grains in the pool",
+	})
+	poolSize = promauto.NewGauge(prometheus.GaugeOpts{
+		Name: "cart_pool_size",
+		Help: "The total number of mutations",
+	})
 )
 
 type GrainPool interface {
@@ -18,6 +32,7 @@ type Ttl struct {
 }
 
 type GrainLocalPool struct {
+	gauage   prometheus.Gauge
 	grains   map[CartId]*CartGrain
 	expiry   []Ttl
 	spawn    func(id CartId) (*CartGrain, error)
@@ -26,13 +41,19 @@ type GrainLocalPool struct {
 }
 
 func NewGrainLocalPool(size int, ttl time.Duration, spawn func(id CartId) (*CartGrain, error)) *GrainLocalPool {
+	gauage := promauto.NewGauge(prometheus.GaugeOpts{
+		Name: "cart_grain_pool_usage",
+		Help: "The current usage of the grain pool",
+	})
 	ret := &GrainLocalPool{
+		gauage:   gauage,
 		spawn:    spawn,
 		grains:   make(map[CartId]*CartGrain),
 		expiry:   make([]Ttl, 0),
 		Ttl:      ttl,
 		PoolSize: size,
 	}
+
 	cartPurge := time.NewTicker(time.Minute)
 	go func() {
 		<-cartPurge.C
@@ -95,6 +116,11 @@ func (p *GrainLocalPool) GetGrain(id CartId) (*CartGrain, error) {
 
 		p.grains[id] = grain
 	}
+	l := float64(len(p.grains))
+	ps := float64(p.PoolSize)
+	p.gauage.Set(l / ps)
+	poolGrains.Set(l)
+	poolSize.Set(ps)
 	return grain, err
 }