megacli: prevent crash when drive temperature is N/A

Intel SSD do not report their temperature in MegaCLI output
Drive Temperature : N/A

collector/fixtures/megacli

@@ -0,0 +1,3 @@
+#!/usr/bin/env bash
+
+cat fixtures/megacli_disks.txt

collector/fixtures/megacli_disks.txt

@@ -83,7 +83,7 @@ Foreign State: None
 Device Speed: Unknown 
 Link Speed: Unknown 
 Media Type: Hard Disk Device
-Drive Temperature :37C (98.60 F)
+Drive Temperature : N/A
 PI Eligibility:  No 
 Drive is formatted for PI information:  No
 PI: No PI

collector/megacli.go

@@ -196,17 +196,18 @@ func (c *megaCliCollector) updateDisks() error {
 
 	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 err
-			}
-
 			encStr := strconv.Itoa(enc)
 			slotStr := strconv.Itoa(slot)
 
-			c.driveTemperature.WithLabelValues(encStr, slotStr).Set(t)
+			tStr := slotStats["Drive Temperature"]
+			if strings.Index(tStr, "C") > 0 {
+				tStr = tStr[:strings.Index(tStr, "C")]
+				t, err := strconv.ParseFloat(tStr, 64)
+				if err != nil {
+					return err
+				}
+				c.driveTemperature.WithLabelValues(encStr, slotStr).Set(t)
+			}
 
 			for _, i := range counters {
 				counter, err := strconv.ParseFloat(slotStats[i], 64)

collector/megacli_test.go

@@ -3,8 +3,11 @@
 package collector
 
 import (
+	"flag"
 	"os"
 	"testing"
+
+	"github.com/prometheus/client_golang/prometheus"
 )
 
 const (
@@ -48,7 +51,32 @@ func TestMegaCliDisks(t *testing.T) {
 		t.Fatalf("Unexpected drive temperature: %s", stats[32][0]["Drive Temperature"])
 	}
 
+	if stats[32][1]["Drive Temperature"] != "N/A" {
+		t.Fatalf("Unexpected drive temperature: %s", stats[32][2]["Drive Temperature"])
+	}
+
 	if stats[32][3]["Predictive Failure Count"] != "23" {
 		t.Fatal()
 	}
 }
+
+func TestMegaCliCollectorDoesntCrash(t *testing.T) {
+	if err := flag.Set("collector.megacli.command", "./fixtures/megacli"); err != nil {
+		t.Fatal(err)
+	}
+	collector, err := NewMegaCliCollector()
+	if err != nil {
+		t.Fatal(err)
+	}
+	sink := make(chan prometheus.Metric)
+	go func() {
+		for {
+			<-sink
+		}
+	}()
+
+	err = collector.Update(sink)
+	if err != nil {
+		t.Fatal(err)
+	}
+}