Add metrics (#110)

* Add metrics

* Hide metric url

Co-authored-by: Emanuel Schütze <emanuel@intevation.de>

cmd/autoupdate/main.go

@@ -96,6 +96,10 @@ func run() error {
 	mux := http.NewServeMux()
 	autoupdatehttp.RegisterAll(mux, auth, a, n)
 
+	if err := initMeter(mux); err != nil {
+		log.Fatalf("Can not initialize meter: %v", err)
+	}
+
 	// Create http server.
 	listenAddr := getEnv("AUTOUPDATE_HOST", "") + ":" + getEnv("AUTOUPDATE_PORT", "8002")
 	srv := &http.Server{Addr: listenAddr, Handler: mux}

cmd/autoupdate/ot.go

@@ -0,0 +1,26 @@
+package main
+
+import (
+	"fmt"
+	"net/http"
+	"time"
+
+	"go.opentelemetry.io/contrib/instrumentation/runtime"
+	"go.opentelemetry.io/otel/exporters/metric/prometheus"
+)
+
+func initMeter(mux *http.ServeMux) error {
+	exporter, err := prometheus.InstallNewPipeline(prometheus.Config{})
+	if err != nil {
+		return fmt.Errorf("initialize prometheus pipeline: %w", err)
+	}
+
+	if err := runtime.Start(
+		runtime.WithMinimumReadMemStatsInterval(time.Second),
+	); err != nil {
+		return fmt.Errorf("initialize runtime metrics: %w", err)
+	}
+
+	mux.Handle("/metrics", exporter)
+	return nil
+}

go.mod

@@ -5,4 +5,7 @@ go 1.15
 require (
 	github.com/gomodule/redigo v1.8.3
 	github.com/ostcar/topic v0.3.4-0.20200624102036-bdbe6ddf5dcd
+	go.opentelemetry.io/contrib/instrumentation/runtime v0.16.0
+	go.opentelemetry.io/otel v0.16.0
+	go.opentelemetry.io/otel/exporters/metric/prometheus v0.16.0
 )