new status command

Add support for running the `status` command and processing the server
response data.
Add new metric for the number of jails.

src/exporter.go

@@ -54,6 +54,11 @@ var (
 		"Check if the fail2ban server is up",
 		nil, nil,
 	)
+	metricJailCount = prometheus.NewDesc(
+		prometheus.BuildFQName(sockNamespace, "", "jail_count"),
+		"Number of defined jails",
+		nil, nil,
+	)
 )
 
 type Exporter struct {
@@ -73,6 +78,7 @@ func (e *Exporter) Describe(ch chan<- *prometheus.Desc) {
 	}
 	if e.socket != nil {
 		ch <- metricServerPing
+		ch <- metricJailCount
 	}
 }
 
@@ -86,6 +92,7 @@ func (e *Exporter) Collect(ch chan<- prometheus.Metric) {
 	}
 	if e.socket != nil {
 		e.collectServerPingMetric(ch)
+		e.collectJailCountMetric(ch)
 	}
 }
 
@@ -164,6 +171,17 @@ func (e *Exporter) collectServerPingMetric(ch chan<- prometheus.Metric) {
 	)
 }
 
+func (e *Exporter) collectJailCountMetric(ch chan<- prometheus.Metric) {
+	jails, err := e.socket.GetJails()
+	var count float64 = 0
+	if err == nil {
+		count = float64(len(jails))
+	}
+	ch <- prometheus.MustNewConstMetric(
+		metricJailCount, prometheus.GaugeValue, count,
+	)
+}
+
 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)

src/socket/fail2banSocket.go

@@ -3,7 +3,8 @@ package socket
 import (
 	"log"
 	"net"
-
+	"fmt"
+	"strings"
 	"github.com/kisielk/og-rek"
 	"github.com/nlpodyssey/gopickle/types"
 )
@@ -37,6 +38,36 @@ func (s *Fail2BanSocket) Ping() bool {
 		}
 		log.Printf("unexpected response data: %s", t)
 	}
-	log.Printf("unexpected response format - cannot parse: %v", response)
+	log.Printf("(%s) unexpected response format - cannot parse: %v", pingCommand, response)
 	return false
 }
+
+func (s *Fail2BanSocket) GetJails() ([]string, error) {
+	response, err := s.sendCommand([]string{statusCommand})
+	if err != nil {
+		return nil, err
+	}
+
+	if lvl1, ok := response.(*types.Tuple); ok {
+		if lvl2, ok := lvl1.Get(1).(*types.List); ok {
+			if lvl3, ok := lvl2.Get(1).(*types.Tuple); ok {
+				if lvl4, ok := lvl3.Get(1).(string); ok {
+					splitJails := strings.Split(lvl4, ",")
+					return trimSpaceForAll(splitJails), nil
+				}
+			}
+		}
+	}
+	return nil, newBadFormatError(statusCommand, response)
+}
+
+func newBadFormatError(command string, data interface{}) error {
+	return fmt.Errorf("(%s) unexpected response format - cannot parse: %v", command, data)
+}
+
+func trimSpaceForAll(slice []string) []string {
+	for i := range slice {
+		slice[i] = strings.TrimSpace(slice[i])
+	}
+	return slice
+}

src/socket/protocol.go

@@ -10,6 +10,7 @@ import (
 const (
 	commandTerminator    = "<F2B_END_COMMAND>"
 	pingCommand          = "ping"
+	statusCommand        = "status"
 	socketReadBufferSize = 1024
 )