feat: improve prometheus variable naming

This commit enhances Prometheus variable naming by adding the device as
a label instead of including it in the variable name. This change is made
to accommodate the dynamic nature of UNIX devices that may change with
reboots.

liquidctl-exporter.go

@@ -25,7 +25,7 @@ const (
 )
 
 var (
-	defaultPort      = "9530"
+	defaultPort      = "9531"
 	defaultInterval  = "10"
 	defaultLiquidCMD = "/usr/local/bin/liquidctl"
 )
@@ -46,7 +46,7 @@ type status struct {
 }
 
 // Metrics store per device ({deviceID: {metricID: prom.Gauge}})
-var devices = map[string]map[string]prometheus.Gauge{}
+var devices = map[string]map[string]*prometheus.GaugeVec{}
 
 // path to liquidctl executable
 var path string
@@ -63,19 +63,20 @@ func init() {
 	// Register metrics available for each liquidctl device
 	for _, d := range liquidctl_stats() {
 		dname := deviceName(d.Address)
-		devices[dname] = map[string]prometheus.Gauge{}
+		devices[dname] = map[string]*prometheus.GaugeVec{}
 		for _, m := range d.Status {
 			name := metricName(m.Key, dname)
 
 			// Register metrics based on type.
 			switch t := m.Value.(type) {
 			case float64:
 				log.Infof("Registering metric '%s' for '%s' device", name, dname)
-				devices[dname][name] = prometheus.NewGauge(
+				devices[dname][name] = prometheus.NewGaugeVec(
 					prometheus.GaugeOpts{
 						Name: name,
 						Help: fmt.Sprintf("%s %s (%s).", d.Description, m.Key, m.Unit),
 					},
+					[]string{"device"},
 				)
 				prometheus.MustRegister(devices[dname][name])
 			default: // Currently only float64 are implemented
@@ -122,7 +123,7 @@ func main() {
 				// Push metric to db if it was registered
 				_, ok := devices[dname][name]
 				if ok {
-					devices[dname][name].Set(m.Value.(float64))
+					devices[dname][name].WithLabelValues(dname).Set(m.Value.(float64))
 				}
 			}
 		}
@@ -154,7 +155,7 @@ func metricName(n, device string) string {
 	// trim + signes
 	name = strings.Trim(strings.ToLower(name), "+")
 	// Append common prefix for all metrics
-	name = fmt.Sprintf("%s_%s_%s", metricPrefix, device, name)
+	name = fmt.Sprintf("%s_%s", metricPrefix, name)
 	// trimming dots by split+join
 	return strings.Join(strings.Split(name, "."), "")
 }