Collect at every scrape, rather than at regular intervals.

Switch to Update using the Collecter Collect interface, due to not knowing all
metricnames in all modules beforehand we can't use Describe and thus the full
Collecter interface.

Remove 'updates', it's meaning varies by module and doesn't add much.

collector/megacli.go

@@ -130,104 +130,92 @@ func NewMegaCliCollector(config Config) (Collector, error) {
 		config: config,
 		cli:    cli,
 	}
-
-	if _, err := prometheus.RegisterOrGet(driveTemperature); err != nil {
-		return nil, err
-	}
-	if _, err := prometheus.RegisterOrGet(driveCounters); err != nil {
-		return nil, err
-	}
-	if _, err := prometheus.RegisterOrGet(drivePresence); err != nil {
-		return nil, err
-	}
 	return &c, nil
 }
 
-func (c *megaCliCollector) Update() (updates int, err error) {
-	au, err := c.updateAdapter()
+func (c *megaCliCollector) Update(ch chan<- prometheus.Metric) (err error) {
+	err = c.updateAdapter()
 	if err != nil {
-		return au, err
+		return err
 	}
-	du, err := c.updateDisks()
-	return au + du, err
+	err = c.updateDisks()
+	driveTemperature.Collect(ch)
+	driveCounters.Collect(ch)
+	drivePresence.Collect(ch)
+	return err
 }
 
-func (c *megaCliCollector) updateAdapter() (int, error) {
+func (c *megaCliCollector) updateAdapter() error {
 	cmd := exec.Command(c.cli, "-AdpAllInfo", "-aALL")
 	pipe, err := cmd.StdoutPipe()
 	if err != nil {
-		return 0, err
+		return err
 	}
 
 	if err := cmd.Start(); err != nil {
-		return 0, err
+		return err
 	}
 
 	stats, err := parseMegaCliAdapter(pipe)
 	if err != nil {
-		return 0, err
+		return err
 	}
 	if err := cmd.Wait(); err != nil {
-		return 0, err
+		return err
 	}
 
-	updates := 0
 	for k, v := range stats["Device Present"] {
 		value, err := strconv.ParseFloat(v, 64)
 		if err != nil {
-			return updates, err
+			return err
 		}
 		drivePresence.WithLabelValues(k).Set(value)
-		updates++
 	}
-	return updates, nil
+	return nil
 }
 
-func (c *megaCliCollector) updateDisks() (int, error) {
+func (c *megaCliCollector) updateDisks() error {
 	cmd := exec.Command(c.cli, "-PDList", "-aALL")
 	pipe, err := cmd.StdoutPipe()
 	if err != nil {
-		return 0, err
+		return err
 	}
 
 	if err := cmd.Start(); err != nil {
-		return 0, err
+		return err
 	}
 
 	stats, err := parseMegaCliDisks(pipe)
 	if err != nil {
-		return 0, err
+		return err
 	}
 	if err := cmd.Wait(); err != nil {
-		return 0, err
+		return err
 	}
 
-	updates := 0
 	for enc, encStats := range stats {
 		for slot, slotStats := range encStats {
 			tStr := slotStats["Drive Temperature"]
 			tStr = tStr[:strings.Index(tStr, "C")]
 			t, err := strconv.ParseFloat(tStr, 64)
 			if err != nil {
-				return updates, err
+				return err
 			}
 
 			encStr := strconv.Itoa(enc)
 			slotStr := strconv.Itoa(slot)
 
 			driveTemperature.WithLabelValues(encStr, slotStr).Set(t)
-			updates++
 
 			for _, c := range counters {
 				counter, err := strconv.ParseFloat(slotStats[c], 64)
 				if err != nil {
-					return updates, err
+					return err
 				}
 
 				driveCounters.WithLabelValues(encStr, slotStr, c).Set(counter)
-				updates++
 			}
 		}
 	}
-	return updates, nil
+	return nil
 }