feat: improve logging on startup

Update the exporter logging on startup to include the exporter version,
the path to the fail2ban socket, and whether basic-auth is enabled or not.
Fix code printing error messages on invalid CLI parameters to correct line
breaks and correctly print the "usage" information.

src/cfg/cfg.go

@@ -1,7 +1,6 @@
 package cfg
 
 import (
-	"flag"
 	"fmt"
 	"gopkg.in/alecthomas/kingpin.v2"
 	"os"
@@ -100,25 +99,25 @@ func (settings *AppSettings) validateFlags() {
 	var flagsValid = true
 	if !settings.VersionMode {
 		if settings.Fail2BanSocketPath == "" {
-			fmt.Println("fail2ban socket path must not be blank")
+			fmt.Println("error: fail2ban socket path must not be blank")
 			flagsValid = false
 		}
 		if settings.MetricsPort < minServerPort || settings.MetricsPort > maxServerPort {
-			fmt.Printf("invalid server port, must be within %d and %d (found %d)\n",
+			fmt.Printf("error: invalid server port, must be within %d and %d (found %d)\n",
 				minServerPort, maxServerPort, settings.MetricsPort)
 			flagsValid = false
 		}
 		if settings.FileCollectorEnabled && settings.FileCollectorPath == "" {
-			fmt.Printf("file collector directory path must not be empty if collector enabled\n")
+			fmt.Println("error: file collector directory path must not be empty if collector enabled")
 			flagsValid = false
 		}
 		if (len(settings.BasicAuthProvider.username) > 0) != (len(settings.BasicAuthProvider.password) > 0) {
-			fmt.Printf("to enable basic auth both the username and the password must be provided")
+			fmt.Println("error: to enable basic auth both the username and the password must be provided")
 			flagsValid = false
 		}
 	}
 	if !flagsValid {
-		flag.Usage()
+		kingpin.Usage()
 		os.Exit(1)
 	}
 }

src/collector/f2b/collector.go

@@ -16,6 +16,7 @@ type Collector struct {
 }
 
 func NewExporter(appSettings *cfg.AppSettings, exporterVersion string) *Collector {
+	log.Printf("reading metrics from fail2ban socket: %s", appSettings.Fail2BanSocketPath)
 	return &Collector{
 		socketPath:                 appSettings.Fail2BanSocketPath,
 		exporterVersion:            exporterVersion,

src/collector/textfile/collector.go

@@ -25,7 +25,7 @@ func NewCollector(appSettings *cfg.AppSettings) *Collector {
 		fileMap:    make(map[string]*fileData),
 	}
 	if collector.enabled {
-		log.Printf("collector.textfile directory: %s", collector.folderPath)
+		log.Printf("reading textfile metrics from: %s", collector.folderPath)
 	}
 	return collector
 }

src/exporter.go

@@ -55,8 +55,8 @@ func main() {
 		printAppVersion()
 	} else {
 		addr := fmt.Sprintf("%s:%d", appSettings.MetricsAddress, appSettings.MetricsPort)
-
-		log.Printf("starting fail2ban exporter at %s", addr)
+		log.Printf("fail2ban exporter version %s", version)
+		log.Printf("starting server at %s", addr)
 
 		f2bCollector := f2b.NewExporter(appSettings, version)
 		prometheus.MustRegister(f2bCollector)
@@ -72,6 +72,9 @@ func main() {
 			appSettings.BasicAuthProvider,
 		))
 		log.Printf("metrics available at '%s'", metricsPath)
+		if appSettings.BasicAuthProvider.Enabled() {
+			log.Printf("basic auth enabled")
+		}
 
 		svrErr := make(chan error)
 		go func() {