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.

collector/fixtures/e2e-output.txt

@@ -457,8 +457,6 @@ node_edac_uncorrectable_errors_total{controller="0"} 5
 node_entropy_available_bits 1337
 # HELP node_exporter_build_info A metric with a constant '1' value labeled by version, revision, branch, and goversion from which node_exporter was built.
 # TYPE node_exporter_build_info gauge
-# HELP node_exporter_scrape_duration_seconds node_exporter: Duration of a scrape job.
-# TYPE node_exporter_scrape_duration_seconds summary
 # HELP node_filefd_allocated File descriptor statistics: allocated.
 # TYPE node_filefd_allocated gauge
 node_filefd_allocated 1024
@@ -2072,6 +2070,35 @@ node_procs_blocked 0
 # HELP node_procs_running Number of processes in runnable state.
 # TYPE node_procs_running gauge
 node_procs_running 2
+# HELP node_scrape_collector_duration_seconds node_exporter: Duration of a collector scrape.
+# TYPE node_scrape_collector_duration_seconds gauge
+# HELP node_scrape_collector_success node_exporter: Whether a collector succeeded.
+# TYPE node_scrape_collector_success gauge
+node_scrape_collector_success{collector="bonding"} 1
+node_scrape_collector_success{collector="buddyinfo"} 1
+node_scrape_collector_success{collector="conntrack"} 1
+node_scrape_collector_success{collector="diskstats"} 1
+node_scrape_collector_success{collector="drbd"} 1
+node_scrape_collector_success{collector="edac"} 1
+node_scrape_collector_success{collector="entropy"} 1
+node_scrape_collector_success{collector="filefd"} 1
+node_scrape_collector_success{collector="hwmon"} 1
+node_scrape_collector_success{collector="infiniband"} 1
+node_scrape_collector_success{collector="ksmd"} 1
+node_scrape_collector_success{collector="loadavg"} 1
+node_scrape_collector_success{collector="mdadm"} 1
+node_scrape_collector_success{collector="megacli"} 1
+node_scrape_collector_success{collector="meminfo"} 1
+node_scrape_collector_success{collector="meminfo_numa"} 1
+node_scrape_collector_success{collector="mountstats"} 1
+node_scrape_collector_success{collector="netdev"} 1
+node_scrape_collector_success{collector="netstat"} 1
+node_scrape_collector_success{collector="nfs"} 1
+node_scrape_collector_success{collector="sockstat"} 1
+node_scrape_collector_success{collector="stat"} 1
+node_scrape_collector_success{collector="textfile"} 1
+node_scrape_collector_success{collector="wifi"} 1
+node_scrape_collector_success{collector="zfs"} 1
 # HELP node_sockstat_FRAG_inuse Number of FRAG sockets in state inuse.
 # TYPE node_sockstat_FRAG_inuse gauge
 node_sockstat_FRAG_inuse 0

end-to-end-test.sh

@@ -35,7 +35,7 @@ cd "$(dirname $0)"
 port="$((10000 + (RANDOM % 10000)))"
 tmpdir=$(mktemp -d /tmp/node_exporter_e2e_test.XXXXXX)
 
-skip_re="^(go_|node_exporter_|process_|node_textfile_mtime)"
+skip_re="^(go_|node_exporter_build_info|node_scrape_collector_duration_seconds|process_|node_textfile_mtime)"
 
 keep=0; update=0; verbose=0
 while getopts 'hkuv' opt

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) {