update ping command to return error

Update the ping command to return errors instead of logging them.

src/exporter.go

@@ -196,8 +196,8 @@ func (e *Exporter) collectEnabledJailMetrics(ch chan<- prometheus.Metric) {
 func (e *Exporter) collectServerUpMetric(ch chan<- prometheus.Metric, s *socket.Fail2BanSocket) {
 	var serverUp float64 = 0
 	if s != nil {
-		pingSuccess := s.Ping()
-		if pingSuccess {
+		pingSuccess, err := s.Ping()
+		if err == nil && pingSuccess {
 			serverUp = 1
 		}
 	}

src/socket/fail2banSocket.go

@@ -36,21 +36,19 @@ func (s *Fail2BanSocket) Close() error {
 	return s.socket.Close()
 }
 
-func (s *Fail2BanSocket) Ping() bool {
+func (s *Fail2BanSocket) Ping() (bool, error) {
 	response, err := s.sendCommand([]string{pingCommand, "100"})
 	if err != nil {
-		log.Printf("server ping failed: %v", err)
-		return false
+		return false, newConnectionError(pingCommand, err)
 	}
 
 	if t, ok := response.(*types.Tuple); ok {
 		if (*t)[1] == "pong" {
-			return true
+			return true, nil
 		}
-		log.Printf("unexpected response data: %s", t)
+		return false, fmt.Errorf("unexpected response data (expecting 'pong'): %s", (*t)[1])
 	}
-	log.Printf("(%s) unexpected response format - cannot parse: %v", pingCommand, response)
-	return false
+	return false, newBadFormatError(pingCommand, response)
 }
 
 func (s *Fail2BanSocket) GetJails() ([]string, error) {
@@ -125,6 +123,10 @@ func newBadFormatError(command string, data interface{}) error {
 	return fmt.Errorf("(%s) unexpected response format - cannot parse: %v", command, data)
 }
 
+func newConnectionError(command string, err error) error {
+	return fmt.Errorf("(%s) failed to send command through socket: %v", err)
+}
+
 func trimSpaceForAll(slice []string) []string {
 	for i := range slice {
 		slice[i] = strings.TrimSpace(slice[i])