Prometheus metrics: allow custom channel, namespace and registry

lib/metrics/prometheus.go

@@ -3,45 +3,72 @@ package metrics
 import (
 	"github.com/eko/gocache/lib/v4/codec"
 	"github.com/prometheus/client_golang/prometheus"
-	"github.com/prometheus/client_golang/prometheus/promauto"
 )
 
 const (
-	namespaceCache = "cache"
+	defaultNamespace = "cache"
 )
 
-var cacheCollector *prometheus.GaugeVec = initCacheCollector(namespaceCache)
-
 // Prometheus represents the prometheus struct for collecting metrics
 type Prometheus struct {
 	service      string
+	namespace    string
 	collector    *prometheus.GaugeVec
+	registerer   prometheus.Registerer
 	codecChannel chan codec.CodecInterface
 }
 
-func initCacheCollector(namespace string) *prometheus.GaugeVec {
-	c := promauto.NewGaugeVec(
+// PrometheusOption is a type for defining Prometheus options
+type PrometheusOption func(*Prometheus)
+
+// WithCodecChannel sets the prometheus codec channel
+func WithCodecChannel(codecChannel chan codec.CodecInterface) PrometheusOption {
+	return func(m *Prometheus) {
+		m.codecChannel = codecChannel
+	}
+}
+
+// WithNamespace sets the prometheus namespace
+func WithNamespace(namespace string) PrometheusOption {
+	return func(m *Prometheus) {
+		m.namespace = namespace
+	}
+}
+
+// WithRegisterer sets the prometheus registerer
+func WithRegisterer(registerer prometheus.Registerer) PrometheusOption {
+	return func(m *Prometheus) {
+		m.registerer = registerer
+	}
+}
+
+// NewPrometheus initializes a new prometheus metric instance
+func NewPrometheus(service string, options ...PrometheusOption) *Prometheus {
+	instance := &Prometheus{
+		namespace:    defaultNamespace,
+		registerer:   prometheus.DefaultRegisterer,
+		service:      service,
+		codecChannel: make(chan codec.CodecInterface, 10000),
+	}
+
+	for _, option := range options {
+		option(instance)
+	}
+
+	instance.collector = prometheus.NewGaugeVec(
 		prometheus.GaugeOpts{
 			Name:      "collector",
-			Namespace: namespace,
+			Namespace: instance.namespace,
 			Help:      "This represent the number of items in cache",
 		},
 		[]string{"service", "store", "metric"},
 	)
-	return c
-}
 
-// NewPrometheus initializes a new prometheus metric instance
-func NewPrometheus(service string) *Prometheus {
-	prometheus := &Prometheus{
-		service:      service,
-		collector:    cacheCollector,
-		codecChannel: make(chan codec.CodecInterface, 10000),
-	}
+	instance.registerer.MustRegister(instance.collector)
 
-	go prometheus.recorder()
+	go instance.recorder()
 
-	return prometheus
+	return instance
 }
 
 // Record records a metric in prometheus by specifying the store name, metric name and value

lib/metrics/prometheus_test.go

@@ -23,12 +23,47 @@ func TestNewPrometheus(t *testing.T) {
 	assert.IsType(t, new(Prometheus), metrics)
 
 	assert.Equal(t, serviceName, metrics.service)
+	assert.Equal(t, defaultNamespace, metrics.namespace)
+	assert.Equal(t, prometheus.DefaultRegisterer, metrics.registerer)
+
+	assert.IsType(t, new(prometheus.GaugeVec), metrics.collector)
+}
+
+func TestNewPrometheus_WithOptions(t *testing.T) {
+	// Given
+	serviceName := "my-test-service-name"
+
+	customNamespace := "my_custom_namespace"
+	customRegistry := prometheus.NewRegistry()
+	customChannel := make(chan codec.CodecInterface, 100)
+
+	// When
+	metrics := NewPrometheus(
+		serviceName,
+		WithCodecChannel(customChannel),
+		WithNamespace(customNamespace),
+		WithRegisterer(customRegistry),
+	)
+
+	// Then
+	assert.IsType(t, new(Prometheus), metrics)
+
+	assert.Equal(t, serviceName, metrics.service)
+	assert.Equal(t, customChannel, metrics.codecChannel)
+	assert.Equal(t, customNamespace, metrics.namespace)
+	assert.Equal(t, customRegistry, metrics.registerer)
+
 	assert.IsType(t, new(prometheus.GaugeVec), metrics.collector)
 }
 
 func TestRecord(t *testing.T) {
 	// Given
-	metrics := NewPrometheus("my-test-service-name")
+	customRegistry := prometheus.NewRegistry()
+
+	metrics := NewPrometheus(
+		"my-test-service-name",
+		WithRegisterer(customRegistry),
+	)
 
 	// When
 	metrics.record("redis", "hit_count", 6)
@@ -65,7 +100,12 @@ func TestRecordFromCodec(t *testing.T) {
 	testCodec.EXPECT().GetStats().Return(stats)
 	testCodec.EXPECT().GetStore().Return(redisStore)
 
-	metrics := NewPrometheus("my-test-service-name")
+	customRegistry := prometheus.NewRegistry()
+
+	metrics := NewPrometheus(
+		"my-test-service-name",
+		WithRegisterer(customRegistry),
+	)
 
 	// When
 	metrics.RecordFromCodec(testCodec)