new metric for response of server ping

Add a new metric to report back the response of the `ping` command.

src/exporter.go

@@ -3,15 +3,20 @@ package main
 import (
 	"fail2ban-prometheus-exporter/cfg"
 	fail2banDb "fail2ban-prometheus-exporter/db"
+	"fail2ban-prometheus-exporter/socket"
 	"fmt"
+	"log"
+	"net/http"
+
 	_ "github.com/mattn/go-sqlite3"
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/promhttp"
-	"log"
-	"net/http"
 )
 
-const namespace = "fail2ban"
+const (
+	namespace     = "fail2ban"
+	sockNamespace = "f2b"
+)
 
 var (
 	version = "dev"
@@ -44,10 +49,16 @@ var (
 		"Number of errors found since startup.",
 		[]string{"type"}, nil,
 	)
+	metricServerPing = prometheus.NewDesc(
+		prometheus.BuildFQName(sockNamespace, "", "up"),
+		"Check if the fail2ban server is up",
+		nil, nil,
+	)
 )
 
 type Exporter struct {
 	db           *fail2banDb.Fail2BanDB
+	socket       *socket.Fail2BanSocket
 	lastError    error
 	dbErrorCount int
 }
@@ -58,6 +69,7 @@ func (e *Exporter) Describe(ch chan<- *prometheus.Desc) {
 	ch <- metricBannedIpsPerJail
 	ch <- metricEnabledJails
 	ch <- metricErrorCount
+	ch <- metricServerPing
 }
 
 func (e *Exporter) Collect(ch chan<- prometheus.Metric) {
@@ -66,6 +78,7 @@ func (e *Exporter) Collect(ch chan<- prometheus.Metric) {
 	e.collectEnabledJailMetrics(ch)
 	e.collectUpMetric(ch)
 	e.collectErrorCountMetric(ch)
+	e.collectServerPingMetric(ch)
 }
 
 func (e *Exporter) collectUpMetric(ch chan<- prometheus.Metric) {
@@ -132,6 +145,17 @@ func (e *Exporter) collectEnabledJailMetrics(ch chan<- prometheus.Metric) {
 	}
 }
 
+func (e *Exporter) collectServerPingMetric(ch chan<- prometheus.Metric) {
+	pingSuccess := e.socket.Ping()
+	var pingSuccessInt float64 = 1
+	if !pingSuccess {
+		pingSuccessInt = 0
+	}
+	ch <- prometheus.MustNewConstMetric(
+		metricServerPing, prometheus.GaugeValue, pingSuccessInt,
+	)
+}
+
 func printAppVersion() {
 	fmt.Println(version)
 	fmt.Printf("    build date:  %s\r\n    commit hash: %s\r\n    built by:    %s\r\n", date, commit, builtBy)
@@ -146,6 +170,7 @@ func main() {
 
 		exporter := &Exporter{
 			db: fail2banDb.MustConnectToDb(appSettings.Fail2BanDbPath),
+			socket: socket.MustConnectToSocket(appSettings.Fail2BanSocketPath),
 		}
 		prometheus.MustRegister(exporter)