refactor: Review metrics endpoints (#1770)

Signed-off-by: Alexei Dodon <adodon@cisco.com>

pkg/extensions/extension_metrics.go

@@ -8,12 +8,12 @@ import (
 	"github.com/prometheus/client_golang/prometheus/promhttp"
 
 	"zotregistry.io/zot/pkg/api/config"
+	"zotregistry.io/zot/pkg/extensions/monitoring"
 	"zotregistry.io/zot/pkg/log"
 )
 
 func EnableMetricsExtension(config *config.Config, log log.Logger, rootDir string) {
-	if config.Extensions.Metrics != nil &&
-		*config.Extensions.Metrics.Enable &&
+	if config.IsMetricsEnabled() &&
 		config.Extensions.Metrics.Prometheus != nil {
 		if config.Extensions.Metrics.Prometheus.Path == "" {
 			config.Extensions.Metrics.Prometheus.Path = "/metrics"
@@ -26,11 +26,11 @@ func EnableMetricsExtension(config *config.Config, log log.Logger, rootDir strin
 }
 
 func SetupMetricsRoutes(config *config.Config, router *mux.Router,
-	authFunc mux.MiddlewareFunc, log log.Logger,
+	authFunc mux.MiddlewareFunc, log log.Logger, metrics monitoring.MetricServer,
 ) {
 	log.Info().Msg("setting up metrics routes")
 
-	if config.Extensions.Metrics != nil && *config.Extensions.Metrics.Enable {
+	if config.IsMetricsEnabled() {
 		extRouter := router.PathPrefix(config.Extensions.Metrics.Prometheus.Path).Subrouter()
 		extRouter.Use(authFunc)
 		extRouter.Methods("GET").Handler(promhttp.Handler())

pkg/extensions/extension_metrics_disabled.go

@@ -4,9 +4,13 @@
 package extensions
 
 import (
+	"net/http"
+
 	"github.com/gorilla/mux"
 
 	"zotregistry.io/zot/pkg/api/config"
+	zcommon "zotregistry.io/zot/pkg/common"
+	"zotregistry.io/zot/pkg/extensions/monitoring"
 	"zotregistry.io/zot/pkg/log"
 )
 
@@ -18,8 +22,12 @@ func EnableMetricsExtension(config *config.Config, log log.Logger, rootDir strin
 
 // SetupMetricsRoutes ...
 func SetupMetricsRoutes(conf *config.Config, router *mux.Router,
-	authFunc mux.MiddlewareFunc, log log.Logger,
+	authFunc mux.MiddlewareFunc, log log.Logger, metrics monitoring.MetricServer,
 ) {
-	log.Warn().Msg("skipping setting up metrics routes because given zot binary doesn't include this feature," +
-		"please build a binary that does so")
+	getMetrics := func(w http.ResponseWriter, r *http.Request) {
+		m := metrics.ReceiveMetrics()
+		zcommon.WriteJSON(w, http.StatusOK, m)
+	}
+
+	router.HandleFunc("/metrics", getMetrics).Methods("GET")
 }

pkg/extensions/monitoring/minimal_client.go

@@ -60,7 +60,7 @@ func NewMetricsClient(config *MetricsConfig, logger log.Logger) *MetricsClient {
 
 func (mc *MetricsClient) GetMetrics() (*MetricsInfo, error) {
 	metrics := &MetricsInfo{}
-	if _, err := mc.makeGETRequest(mc.config.Address+"/v2/metrics", metrics); err != nil {
+	if _, err := mc.makeGETRequest(mc.config.Address+"/metrics", metrics); err != nil {
 		return nil, err
 	}