Split native collector into it's component parts and make them enablable.

Last login is disabled by default as it's broken on ubuntu 12.04
Interrupts is disabled by default as it's very granular and we'll have total interrupts from /proc/stat

Allow ignoring devices from diskstats, ignore ram and loop devices by default.

Use glog for logging.

collector/lastlogin.go

@@ -0,0 +1,105 @@
+// +build !nolastLogin
+
+package collector
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"os/exec"
+	"strings"
+	"time"
+
+	"github.com/golang/glog"
+	"github.com/prometheus/client_golang/prometheus"
+)
+
+var (
+	lastSeen = prometheus.NewGauge()
+)
+
+type lastLoginCollector struct {
+	registry prometheus.Registry
+	config   Config
+}
+
+func init() {
+	Factories["lastlogin"] = NewLastLoginCollector
+}
+
+// Takes a config struct and prometheus registry and returns a new Collector exposing
+// load, seconds since last login and a list of tags as specified by config.
+func NewLastLoginCollector(config Config, registry prometheus.Registry) (Collector, error) {
+	c := lastLoginCollector{
+		config:   config,
+		registry: registry,
+	}
+	registry.Register(
+		"node_last_login_time",
+		"The time of the last login.",
+		prometheus.NilLabels,
+		lastSeen,
+	)
+	return &c, nil
+}
+
+func (c *lastLoginCollector) Update() (updates int, err error) {
+	last, err := getLastLoginTime()
+	if err != nil {
+		return updates, fmt.Errorf("Couldn't get last seen: %s", err)
+	}
+	updates++
+	glog.V(1).Infof("Set node_last_login_time: %f", last)
+	lastSeen.Set(nil, last)
+	return updates, err
+}
+
+func getLastLoginTime() (float64, error) {
+	who := exec.Command("who", "/var/log/wtmp", "-l", "-u", "-s")
+
+	output, err := who.StdoutPipe()
+	if err != nil {
+		return 0, err
+	}
+
+	err = who.Start()
+	if err != nil {
+		return 0, err
+	}
+
+	reader := bufio.NewReader(output)
+
+	var last time.Time
+	for {
+		line, isPrefix, err := reader.ReadLine()
+		if err == io.EOF {
+			break
+		}
+		if isPrefix {
+			return 0, fmt.Errorf("line to long: %s(...)", line)
+		}
+
+		fields := strings.Fields(string(line))
+		lastDate := fields[2]
+		lastTime := fields[3]
+
+		dateParts, err := splitToInts(lastDate, "-") // 2013-04-16
+		if err != nil {
+			return 0, fmt.Errorf("Couldn't parse date in line '%s': %s", fields, err)
+		}
+
+		timeParts, err := splitToInts(lastTime, ":") // 11:33
+		if err != nil {
+			return 0, fmt.Errorf("Couldn't parse time in line '%s': %s", fields, err)
+		}
+
+		last_t := time.Date(dateParts[0], time.Month(dateParts[1]), dateParts[2], timeParts[0], timeParts[1], 0, 0, time.UTC)
+		last = last_t
+	}
+	err = who.Wait()
+	if err != nil {
+		return 0, err
+	}
+
+	return float64(last.Unix()), nil
+}