Revamp the netdev collector to use throw-away ConstMetrics.

collector/netdev_linux.go

@@ -17,19 +17,20 @@ import (
 )
 
 const (
-	procNetDev      = "/proc/net/dev"
-	netDevSubsystem = "network"
+	procNetDev = "/proc/net/dev"
+	subsystem  = "network"
 )
 
 var (
-	fieldSep             = regexp.MustCompile("[ :] *")
-	netdevIgnoredDevices = flag.String("collector.netdev.ignored-devices", "^$", "Regexp of net devices to ignore for netdev collector.")
+	fieldSep	     = regexp.MustCompile("[ :] *")
+	netdevIgnoredDevices = flag.String(
+		"collector.netdev.ignored-devices", "^$",
+		"Regexp of net devices to ignore for netdev collector.")
 )
 
 type netDevCollector struct {
 	ignoredDevicesPattern *regexp.Regexp
-
-	metrics map[string]*prometheus.GaugeVec
+	metricDescs map[string]*prometheus.Desc
 }
 
 func init() {
@@ -39,9 +40,10 @@ func init() {
 // Takes a prometheus registry and returns a new Collector exposing
 // network device stats.
 func NewNetDevCollector() (Collector, error) {
+	pattern := regexp.MustCompile(*netdevIgnoredDevices)
 	return &netDevCollector{
-		ignoredDevicesPattern: regexp.MustCompile(*netdevIgnoredDevices),
-		metrics:               map[string]*prometheus.GaugeVec{},
+		ignoredDevicesPattern: pattern,
+		metricDescs:	       map[string]*prometheus.Desc{},
 	}, nil
 }
 
@@ -50,36 +52,34 @@ func (c *netDevCollector) Update(ch chan<- prometheus.Metric) (err error) {
 	if err != nil {
 		return fmt.Errorf("Couldn't get netstats: %s", err)
 	}
-	for direction, devStats := range netDev {
-		for dev, stats := range devStats {
-			for t, value := range stats {
-				key := direction + "_" + t
-				if _, ok := c.metrics[key]; !ok {
-					c.metrics[key] = prometheus.NewGaugeVec(
-						prometheus.GaugeOpts{
-							Namespace: Namespace,
-							Subsystem: netDevSubsystem,
-							Name:      key,
-							Help:      fmt.Sprintf("%s %s from /proc/net/dev.", t, direction),
-						},
-						[]string{"device"},
-					)
-				}
-				v, err := strconv.ParseFloat(value, 64)
-				if err != nil {
-					return fmt.Errorf("Invalid value %s in netstats: %s", value, err)
-				}
-				c.metrics[key].WithLabelValues(dev).Set(v)
+	for dev, devStats := range netDev {
+		for key, value := range devStats {
+                        desc, ok := c.metricDescs[key]
+                        if !ok {
+                                desc = prometheus.NewDesc(
+                                        prometheus.BuildFQName(
+                                                Namespace, subsystem, key),
+                                        fmt.Sprintf(
+                                                "%s from /proc/net/dev.", key),
+                                        []string{"device"},
+                                        nil,
+                                )
+                                c.metricDescs[key] = desc
+                        }
+			v, err := strconv.ParseFloat(value, 64)
+			if err != nil {
+				return fmt.Errorf(
+					"Invalid value %s in netstats: %s",
+					value, err)
 			}
+			ch <- prometheus.MustNewConstMetric(
+				desc, prometheus.GaugeValue, v, dev)
 		}
 	}
-	for _, m := range c.metrics {
-		m.Collect(ch)
-	}
-	return err
+	return nil
 }
 
-func getNetDevStats(ignore *regexp.Regexp) (map[string]map[string]map[string]string, error) {
+func getNetDevStats(ignore *regexp.Regexp) (map[string]map[string]string, error) {
 	file, err := os.Open(procNetDev)
 	if err != nil {
 		return nil, err
@@ -89,11 +89,7 @@ func getNetDevStats(ignore *regexp.Regexp) (map[string]map[string]map[string]str
 	return parseNetDevStats(file, ignore)
 }
 
-func parseNetDevStats(r io.Reader, ignore *regexp.Regexp) (map[string]map[string]map[string]string, error) {
-	netDev := map[string]map[string]map[string]string{}
-	netDev["transmit"] = map[string]map[string]string{}
-	netDev["receive"] = map[string]map[string]string{}
-
+func parseNetDevStats(r io.Reader, ignore *regexp.Regexp) (map[string]map[string]string, error) {
 	scanner := bufio.NewScanner(r)
 	scanner.Scan() // skip first header
 	scanner.Scan()
@@ -102,7 +98,9 @@ func parseNetDevStats(r io.Reader, ignore *regexp.Regexp) (map[string]map[string
 		return nil, fmt.Errorf("Invalid header line in %s: %s",
 			procNetDev, scanner.Text())
 	}
+
 	header := strings.Fields(parts[1])
+	netDev := map[string]map[string]string{}
 	for scanner.Scan() {
 		line := strings.TrimLeft(string(scanner.Text()), " ")
 		parts := fieldSep.Split(line, -1)
@@ -112,30 +110,15 @@ func parseNetDevStats(r io.Reader, ignore *regexp.Regexp) (map[string]map[string
 		}
 
 		dev := parts[0][:len(parts[0])]
-		receive, err := parseNetDevLine(parts[1:len(header)+1], header)
-		if err != nil {
-			return nil, err
-		}
-
-		transmit, err := parseNetDevLine(parts[len(header)+1:], header)
-		if err != nil {
-			return nil, err
-		}
-
 		if ignore.MatchString(dev) {
 			log.Debugf("Ignoring device: %s", dev)
 			continue
 		}
-		netDev["transmit"][dev] = transmit
-		netDev["receive"][dev] = receive
+		netDev[dev] = map[string]string{}
+		for i, v := range header {
+			netDev[dev]["receive_" + v] = parts[i+1]
+			netDev[dev]["transmit_" + v] = parts[i+1+len(header)]
+		}
 	}
 	return netDev, nil
 }
-
-func parseNetDevLine(parts []string, header []string) (map[string]string, error) {
-	devStats := map[string]string{}
-	for i, v := range parts {
-		devStats[header[i]] = v
-	}
-	return devStats, nil
-}