NETOBSERV-765 Restore metrics (#315)

* NETOBSERV-765 Restore metrics

* Use dedicated port for metrics

cmd/plugin-backend.go

@@ -21,6 +21,7 @@ var (
 	buildDate    = "unknown"
 	app          = "netobserv-console-plugin"
 	port         = flag.Int("port", 9001, "server port to listen on (default: 9001)")
+	metricsPort  = flag.Int("metrics-port", 9002, "Metrics (prometheus) server port to listen on (default: 9002)")
 	cert         = flag.String("cert", "", "cert file path to enable TLS (disabled by default)")
 	key          = flag.String("key", "", "private key file path to enable TLS (disabled by default)")
 	corsOrigin   = flag.String("cors-origin", "*", "CORS allowed origin (default: *)")
@@ -111,6 +112,12 @@ func main() {
 		log.WithError(err).Fatal("auth checker error")
 	}
 
+	go server.StartMetrics(&server.MetricsConfig{
+		Port:           *metricsPort,
+		CertFile:       *cert,
+		PrivateKeyFile: *key,
+	})
+
 	server.Start(&server.Config{
 		Port:             *port,
 		CertFile:         *cert,

pkg/server/metrics_server.go

@@ -0,0 +1,40 @@
+package server
+
+import (
+	"crypto/tls"
+	"fmt"
+	"net/http"
+
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+	"github.com/sirupsen/logrus"
+)
+
+var mlog = logrus.WithField("module", "metrics-server")
+
+type MetricsConfig struct {
+	Port           int
+	CertFile       string
+	PrivateKeyFile string
+}
+
+func StartMetrics(cfg *MetricsConfig) {
+	promServer := &http.Server{
+		Addr: fmt.Sprintf(":%d", cfg.Port),
+		// TLS clients must use TLS 1.2 or higher
+		TLSConfig: &tls.Config{
+			MinVersion: tls.VersionTLS12,
+		},
+	}
+
+	// The Handler function provides a default handler to expose metrics
+	// via an HTTP server. "/metrics" is the usual endpoint for that.
+	http.Handle("/metrics", promhttp.Handler())
+
+	if cfg.CertFile != "" && cfg.PrivateKeyFile != "" {
+		mlog.Infof("listening on https://:%d", cfg.Port)
+		panic(promServer.ListenAndServeTLS(cfg.CertFile, cfg.PrivateKeyFile))
+	} else {
+		mlog.Infof("listening on http://:%d", cfg.Port)
+		panic(promServer.ListenAndServe())
+	}
+}

pkg/server/routes.go

@@ -41,8 +41,6 @@ func setupRoutes(cfg *Config, authChecker auth.Checker) *mux.Router {
 	api.HandleFunc("/resources/kind/{kind}/names", handler.GetNames(&cfg.Loki))
 	api.HandleFunc("/frontend-config", handler.GetConfig(cfg.FrontendConfig))
 
-	// Temporary removal of metrics
-	//	r.Handle("/metrics", promhttp.Handler())
 	r.PathPrefix("/").Handler(http.FileServer(http.Dir("./web/dist/")))
 	return r
 }