chore(exporter): rework exporter to fix wrong histogram usage and cache metric data

main.go

@@ -6,6 +6,7 @@ import (
 	"os"
 	"os/signal"
 	"syscall"
+	"time"
 
 	apiv1 "git.ar21.de/yolokube/country-geo-locations/api/v1"
 	"git.ar21.de/yolokube/country-geo-locations/internal/cache"
@@ -17,29 +18,24 @@ import (
 	"github.com/go-chi/chi/v5"
 	"github.com/go-chi/chi/v5/middleware"
 	"github.com/go-chi/render"
-	"github.com/prometheus/client_golang/prometheus"
-	"github.com/prometheus/client_golang/prometheus/promhttp"
 )
 
 func main() {
 	cli := cmd.CLI{}
-	queue := exporter.NewRequestDataQueue()
-	appSettings, err := cli.Parse()
+	config, err := cli.Parse()
 	if err != nil {
 		log.Fatal(err)
 	}
 
 	handleGracefulShutdown()
 
-	exporterMiddleware := exporter.NewMiddleware(queue)
 	r := chi.NewRouter()
 	r.Use(middleware.RequestID)
 	r.Use(middleware.Logger)
 	r.Use(middleware.Recoverer)
-	r.Use(exporterMiddleware)
 	r.Use(render.SetContentType(render.ContentTypeJSON))
 
-	ctx := downloader.NewContext(appSettings.DataFile, appSettings.DataURL)
+	ctx := downloader.NewContext(config.DataFile, config.DataURL)
 	if !ctx.FileExists() {
 		if downloadErr := ctx.Download(); downloadErr != nil {
 			log.Fatal(downloadErr)
@@ -47,24 +43,42 @@ func main() {
 		log.Printf("saved file to %s\n", ctx.Filename)
 	}
 
-	cache := cache.NewCache(appSettings.CacheTTL)
-	db, err := database.NewDatabase(appSettings)
+	cache := cache.NewCache(config.CacheTTL)
+	db, err := database.NewDatabase(config)
 	if err != nil {
 		log.Fatal("database creation failed", err)
 	}
 
-	if appSettings.EnableExporter {
+	if config.EnableExporter {
+		exporter := exporter.NewExporter(config, cache, db)
+		r.Use(exporter.Middleware())
+
+		ticker := time.NewTicker(config.ExporterInterval)
+		exit := make(chan struct{})
 		go func() {
-			err = enableExporter(appSettings, cache, db, queue)
+			for {
+				select {
+				case <-ticker.C:
+					exporter.Collect()
+				case <-exit:
+					ticker.Stop()
+					return
+				}
+			}
+		}()
+		log.Println("prometheus exporter refreshes metric data every", config.ExporterInterval)
+
+		go func() {
+			err = exporter.Start()
 			if err != nil {
 				log.Panic(err)
 			}
 		}()
-		log.Println("prometheus exporter started at", appSettings.ExporterAddress)
+		log.Println("prometheus exporter started at", config.ExporterAddress)
 	}
 
-	log.Println("importing data from file", appSettings.DataFile)
-	err = csvimporter.ImportCSV(appSettings.DataFile, db)
+	log.Println("importing data from file", config.DataFile)
+	err = csvimporter.ImportCSV(config.DataFile, db)
 	if err != nil {
 		log.Fatal("data Import from file failed", err)
 	}
@@ -74,9 +88,9 @@ func main() {
 	r.Mount("/api/v1", apiv1.NewRouter(lh))
 
 	server := &http.Server{
-		Addr:              appSettings.ServerAddress,
+		Addr:              config.ServerAddress,
 		Handler:           r,
-		ReadHeaderTimeout: appSettings.ReadHeaderTimeout,
+		ReadHeaderTimeout: config.ReadHeaderTimeout,
 	}
 
 	log.Println("starting server at", server.Addr)
@@ -85,23 +99,6 @@ func main() {
 	}
 }
 
-func enableExporter(
-	settings *cmd.AppSettings,
-	cache *cache.Cache,
-	db *database.Database,
-	queue *exporter.RequestDataQueue,
-) error {
-	prometheus.MustRegister(exporter.NewCollector(settings, cache, db, queue))
-
-	metricsServer := &http.Server{
-		Addr:              settings.ExporterAddress,
-		Handler:           promhttp.Handler(),
-		ReadHeaderTimeout: settings.ReadHeaderTimeout,
-	}
-
-	return metricsServer.ListenAndServe()
-}
-
 func handleGracefulShutdown() {
 	var signals = make(chan os.Signal, 1)