Change to const metrics

Author: carlpett

exporter.go

@@ -33,31 +33,25 @@ const (
 )
 
 var (
-	scrapeDurations = prometheus.NewGaugeVec(
-		prometheus.GaugeOpts{
-			Namespace: collector.Namespace,
-			Subsystem: "exporter",
-			Name:      "collector_duration_seconds",
-			Help:      "wmi_exporter: Duration of a collection.",
-		},
+	scrapeDurationDesc = prometheus.NewDesc(
+		prometheus.BuildFQName(collector.Namespace, "exporter", "collector_duration_seconds"),
+		"wmi_exporter: Duration of a collection.",
 		[]string{"collector"},
+		nil,
 	)
-	scrapeSuccess = prometheus.NewGaugeVec(
-		prometheus.GaugeOpts{
-			Namespace: collector.Namespace,
-			Subsystem: "exporter",
-			Name:      "collector_success",
-			Help:      "wmi_exporter: Whether the collector was successful.",
-		},
+	scrapeSuccessDesc = prometheus.NewDesc(
+		prometheus.BuildFQName(collector.Namespace, "exporter", "collector_success"),
+		"wmi_exporter: Whether the collector was successful.",
 		[]string{"collector"},
+		nil,
 	)
 )
 
 // Describe sends all the descriptors of the collectors included to
 // the provided channel.
 func (coll WmiCollector) Describe(ch chan<- *prometheus.Desc) {
-	scrapeDurations.Describe(ch)
-	scrapeSuccess.Describe(ch)
+	ch <- scrapeDurationDesc
+	ch <- scrapeSuccessDesc
 }
 
 // Collect sends the collected metrics from each of the collectors to
@@ -73,8 +67,6 @@ func (coll WmiCollector) Collect(ch chan<- prometheus.Metric) {
 		}(name, c)
 	}
 	wg.Wait()
-	scrapeDurations.Collect(ch)
-	scrapeSuccess.Collect(ch)
 }
 
 func filterAvailableCollectors(collectors string) string {
@@ -92,15 +84,27 @@ func execute(name string, c collector.Collector, ch chan<- prometheus.Metric) {
 	begin := time.Now()
 	err := c.Collect(ch)
 	duration := time.Since(begin)
+	var success float64
 
 	if err != nil {
 		log.Errorf("ERROR: %s collector failed after %fs: %s", name, duration.Seconds(), err)
-		scrapeSuccess.WithLabelValues(name).Set(0)
+		success = 0
 	} else {
 		log.Debugf("OK: %s collector succeeded after %fs.", name, duration.Seconds())
-		scrapeSuccess.WithLabelValues(name).Set(1)
+		success = 1
 	}
-	scrapeDurations.WithLabelValues(name).Set(duration.Seconds())
+	ch <- prometheus.MustNewConstMetric(
+		scrapeDurationDesc,
+		prometheus.GaugeValue,
+		duration.Seconds(),
+		name,
+	)
+	ch <- prometheus.MustNewConstMetric(
+		scrapeSuccessDesc,
+		prometheus.GaugeValue,
+		success,
+		name,
+	)
 }
 
 func expandEnabledCollectors(enabled string) []string {