systemd: check version for availability of properties (#1413)

The dbus property 'SystemState' and the timer property 'LastTriggerUSec'
were added in version 212 of systemd.
Check that the version of systemd is higher than 212 before attempting
to query these properties

f755e3b74b
dedabea4b3

Resolves issue #291

Signed-off-by: Paul Gier <pgier@redhat.com>

CHANGELOG.md

@@ -20,6 +20,7 @@
 * [ENHANCEMENT] Include additional XFS runtime statistics. #1423
 * [ENHANCEMENT] Report non-fatal collection errors in the exporter metric. #1439
 * [ENHANCEMENT] Expose IPVS firewall mark as a label #1455
+* [ENHANCEMENT] Add check for systemd version before attempting to query certain metrics. #1413
 * [BUGFIX] Renamed label `state` to `name` on `node_systemd_service_restart_total`. #1393
 * [BUGFIX] Fix netdev nil reference on Darwin #1414
 * [BUGFIX] Strip path.rootfs from mountpoint labels #1421

collector/systemd_linux.go

@@ -19,6 +19,7 @@ import (
 	"fmt"
 	"math"
 	"regexp"
+	"strconv"
 	"strings"
 	"sync"
 	"time"
@@ -29,6 +30,13 @@ import (
 	kingpin "gopkg.in/alecthomas/kingpin.v2"
 )
 
+const (
+	// minSystemdVersionSystemState is the minimum SystemD version for availability of
+	// the 'SystemState' manager property and the timer property 'LastTriggerUSec'
+	// https://github.com/prometheus/node_exporter/issues/291
+	minSystemdVersionSystemState = 212
+)
+
 var (
 	unitWhitelist          = kingpin.Flag("collector.systemd.unit-whitelist", "Regexp of systemd units to whitelist. Units must both match whitelist and not match blacklist to be included.").Default(".+").String()
 	unitBlacklist          = kingpin.Flag("collector.systemd.unit-blacklist", "Regexp of systemd units to blacklist. Units must both match whitelist and not match blacklist to be included.").Default(".+\\.(automount|device|mount|scope|slice)").String()
@@ -50,6 +58,8 @@ type systemdCollector struct {
 	socketAcceptedConnectionsDesc *prometheus.Desc
 	socketCurrentConnectionsDesc  *prometheus.Desc
 	socketRefusedConnectionsDesc  *prometheus.Desc
+	systemdVersionDesc            *prometheus.Desc
+	systemdVersion                int
 	unitWhitelistPattern          *regexp.Regexp
 	unitBlacklistPattern          *regexp.Regexp
 }
@@ -103,9 +113,18 @@ func NewSystemdCollector() (Collector, error) {
 	socketRefusedConnectionsDesc := prometheus.NewDesc(
 		prometheus.BuildFQName(namespace, subsystem, "socket_refused_connections_total"),
 		"Total number of refused socket connections", []string{"name"}, nil)
+	systemdVersionDesc := prometheus.NewDesc(
+		prometheus.BuildFQName(namespace, subsystem, "version"),
+		"Detected systemd version", []string{}, nil)
 	unitWhitelistPattern := regexp.MustCompile(fmt.Sprintf("^(?:%s)$", *unitWhitelist))
 	unitBlacklistPattern := regexp.MustCompile(fmt.Sprintf("^(?:%s)$", *unitBlacklist))
 
+	systemdVersion := getSystemdVersion()
+	if systemdVersion < minSystemdVersionSystemState {
+		log.Warnf("Detected systemd version %v is lower than minimum %v", systemdVersion, minSystemdVersionSystemState)
+		log.Warn("Some systemd state and timer metrics will not be available")
+	}
+
 	return &systemdCollector{
 		unitDesc:                      unitDesc,
 		unitStartTimeDesc:             unitStartTimeDesc,
@@ -118,6 +137,8 @@ func NewSystemdCollector() (Collector, error) {
 		socketAcceptedConnectionsDesc: socketAcceptedConnectionsDesc,
 		socketCurrentConnectionsDesc:  socketCurrentConnectionsDesc,
 		socketRefusedConnectionsDesc:  socketRefusedConnectionsDesc,
+		systemdVersionDesc:            systemdVersionDesc,
+		systemdVersion:                systemdVersion,
 		unitWhitelistPattern:          unitWhitelistPattern,
 		unitBlacklistPattern:          unitBlacklistPattern,
 	}, nil
@@ -127,7 +148,7 @@ func NewSystemdCollector() (Collector, error) {
 // to reduce wait time for responses.
 func (c *systemdCollector) Update(ch chan<- prometheus.Metric) error {
 	begin := time.Now()
-	conn, err := c.newDbus()
+	conn, err := newSystemdDbusConn()
 	if err != nil {
 		return fmt.Errorf("couldn't get dbus connection: %s", err)
 	}
@@ -179,6 +200,7 @@ func (c *systemdCollector) Update(ch chan<- prometheus.Metric) error {
 		}()
 	}
 
+	if c.systemdVersion >= minSystemdVersionSystemState {
 		wg.Add(1)
 		go func() {
 			defer wg.Done()
@@ -186,6 +208,7 @@ func (c *systemdCollector) Update(ch chan<- prometheus.Metric) error {
 			c.collectTimers(conn, ch, units)
 			log.Debugf("systemd collectTimers took %f", time.Since(begin).Seconds())
 		}()
+	}
 
 	wg.Add(1)
 	go func() {
@@ -195,9 +218,15 @@ func (c *systemdCollector) Update(ch chan<- prometheus.Metric) error {
 		log.Debugf("systemd collectSockets took %f", time.Since(begin).Seconds())
 	}()
 
+	if c.systemdVersion >= minSystemdVersionSystemState {
 		begin = time.Now()
 		err = c.collectSystemState(conn, ch)
 		log.Debugf("systemd collectSystemState took %f", time.Since(begin).Seconds())
+	}
+
+	ch <- prometheus.MustNewConstMetric(
+		c.systemdVersionDesc, prometheus.GaugeValue, float64(c.systemdVersion))
+
 	return err
 }
 
@@ -369,7 +398,7 @@ func (c *systemdCollector) collectSystemState(conn *dbus.Conn, ch chan<- prometh
 	return nil
 }
 
-func (c *systemdCollector) newDbus() (*dbus.Conn, error) {
+func newSystemdDbusConn() (*dbus.Conn, error) {
 	if *systemdPrivate {
 		return dbus.NewSystemdConnection()
 	}
@@ -424,3 +453,24 @@ func filterUnits(units []unit, whitelistPattern, blacklistPattern *regexp.Regexp
 
 	return filtered
 }
+
+func getSystemdVersion() int {
+	conn, err := newSystemdDbusConn()
+	if err != nil {
+		log.Warnf("Unable to get systemd dbus connection, defaulting systemd version to 0: %s", err)
+		return 0
+	}
+	defer conn.Close()
+	version, err := conn.GetManagerProperty("Version")
+	if err != nil {
+		log.Warn("Unable to get systemd version property, defaulting to 0")
+		return 0
+	}
+	version = strings.Replace(version, "\"", "", 2)
+	v, err := strconv.Atoi(version)
+	if err != nil {
+		log.Warnf("Got invalid systemd version: %v", version)
+		return 0
+	}
+	return v
+}