Report collector success/failure and duration per scrape. (#516)

This is in line with best practices, and also saves us
63 timeseries on a default Linux setup.

1 files changed, 18 insertions, 14 deletions

diff --git a/node_exporter.go b/node_exporter.go
index 1028ed8..4a7f88a 100644
--- a/node_exporter.go
+++ b/node_exporter.go
@@ -36,14 +36,17 @@ const (
 )
 
 var (
-        scrapeDurations = prometheus.NewSummaryVec(
-                prometheus.SummaryOpts{
-                        Namespace: collector.Namespace,
-                        Subsystem: "exporter",
-                        Name:      "scrape_duration_seconds",
-                        Help:      "node_exporter: Duration of a scrape job.",
-                },
-                []string{"collector", "result"},
+        scrapeDurationDesc = prometheus.NewDesc(
+                prometheus.BuildFQName(collector.Namespace, "scrape", "collector_duration_seconds"),
+                "node_exporter: Duration of a collector scrape.",
+                []string{"collector"},
+                nil,
+        )
+        scrapeSuccessDesc = prometheus.NewDesc(
+                prometheus.BuildFQName(collector.Namespace, "scrape", "collector_success"),
+                "node_exporter: Whether a collector succeeded.",
+                []string{"collector"},
+                nil,
         )
 )
 
@@ -54,7 +57,8 @@ type NodeCollector struct {
 
 // Describe implements the prometheus.Collector interface.
 func (n NodeCollector) Describe(ch chan<- *prometheus.Desc) {
-        scrapeDurations.Describe(ch)
+        ch <- scrapeDurationDesc
+        ch <- scrapeSuccessDesc
 }
 
 // Collect implements the prometheus.Collector interface.
@@ -68,7 +72,6 @@ func (n NodeCollector) Collect(ch chan<- prometheus.Metric) {
                 }(name, c)
         }
         wg.Wait()
-        scrapeDurations.Collect(ch)
 }
 
 func filterAvailableCollectors(collectors string) string {
@@ -86,16 +89,17 @@ func execute(name string, c collector.Collector, ch chan<- prometheus.Metric) {
         begin := time.Now()
         err := c.Update(ch)
         duration := time.Since(begin)
-        var result string
+        var success float64
 
         if err != nil {
                 log.Errorf("ERROR: %s collector failed after %fs: %s", name, duration.Seconds(), err)
-                result = "error"
+                success = 0
         } else {
                 log.Debugf("OK: %s collector succeeded after %fs.", name, duration.Seconds())
-                result = "success"
+                success = 1
         }
-        scrapeDurations.WithLabelValues(name, result).Observe(duration.Seconds())
+        ch <- prometheus.MustNewConstMetric(scrapeDurationDesc, prometheus.GaugeValue, duration.Seconds(), name)
+        ch <- prometheus.MustNewConstMetric(scrapeSuccessDesc, prometheus.GaugeValue, success, name)
 }
 
 func loadCollectors(list string) (map[string]collector.Collector, error) {