Add systemd uptime metric collection (#952)

* Add systemd uptime metric collection

Signed-off-by: Sven Lange <tdl@hadiko.de>

2 files changed, 28 insertions, 0 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 85a0485..2cb808d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,7 @@
 * [FEATURE] Collect NRefused property for systemd socket units (available as of systemd v239)
 * [FEATURE] Collect NRestarts property for systemd service units
 * [FEATURE] Add socket unit stats to systemd collector #968
+* [FEATURE] Collect start time for systemd units
 * [ENHANCEMENT]
 * [BUGFIX]
 
diff --git a/collector/systemd_linux.go b/collector/systemd_linux.go
index 3e16c45..99a10de 100644
--- a/collector/systemd_linux.go
+++ b/collector/systemd_linux.go
@@ -34,6 +34,7 @@ var (
 
 type systemdCollector struct {
         unitDesc                      *prometheus.Desc
+        unitStartTimeDesc             *prometheus.Desc
         systemRunningDesc             *prometheus.Desc
         summaryDesc                   *prometheus.Desc
         nRestartsDesc                 *prometheus.Desc
@@ -59,6 +60,10 @@ func NewSystemdCollector() (Collector, error) {
                 prometheus.BuildFQName(namespace, subsystem, "unit_state"),
                 "Systemd unit", []string{"name", "state"}, nil,
         )
+        unitStartTimeDesc := prometheus.NewDesc(
+                prometheus.BuildFQName(namespace, subsystem, "unit_start_time_seconds"),
+                "Start time of the unit since unix epoch in seconds.", []string{"name"}, nil,
+        )
         systemRunningDesc := prometheus.NewDesc(
                 prometheus.BuildFQName(namespace, subsystem, "system_running"),
                 "Whether the system is operational (see 'systemctl is-system-running')",
@@ -87,6 +92,7 @@ func NewSystemdCollector() (Collector, error) {
 
         return &systemdCollector{
                 unitDesc:                      unitDesc,
+                unitStartTimeDesc:             unitStartTimeDesc,
                 systemRunningDesc:             systemRunningDesc,
                 summaryDesc:                   summaryDesc,
                 nRestartsDesc:                 nRestartsDesc,
@@ -110,6 +116,7 @@ func (c *systemdCollector) Update(ch chan<- prometheus.Metric) error {
 
         units := filterUnits(allUnits, c.unitWhitelistPattern, c.unitBlacklistPattern)
         c.collectUnitStatusMetrics(ch, units)
+        c.collectUnitStartTimeMetrics(ch, units)
         c.collectTimers(ch, units)
         c.collectSockets(ch, units)
 
@@ -160,6 +167,14 @@ func (c *systemdCollector) collectSockets(ch chan<- prometheus.Metric, units []u
         return nil
 }
 
+func (c *systemdCollector) collectUnitStartTimeMetrics(ch chan<- prometheus.Metric, units []unit) {
+        for _, unit := range units {
+                ch <- prometheus.MustNewConstMetric(
+                        c.unitStartTimeDesc, prometheus.GaugeValue,
+                        float64(unit.startTimeUsec)/1e6, unit.Name)
+        }
+}
+
 func (c *systemdCollector) collectTimers(ch chan<- prometheus.Metric, units []unit) error {
         for _, unit := range units {
                 if !strings.HasSuffix(unit.Name, ".timer") {
@@ -198,6 +213,7 @@ func (c *systemdCollector) newDbus() (*dbus.Conn, error) {
 type unit struct {
         dbus.UnitStatus
         lastTriggerUsec     uint64
+        startTimeUsec       uint64
         nRestarts           uint32
         acceptedConnections uint32
         currentConnections  uint32
@@ -261,6 +277,17 @@ func (c *systemdCollector) getAllUnits() ([]unit, error) {
                         unit.refusedConnections = refusedConnectionCount.Value.Value().(uint32)
                 }
 
+                if unit.ActiveState != "active" {
+                        unit.startTimeUsec = 0
+                } else {
+                        timestampValue, err := conn.GetUnitProperty(unit.Name, "ActiveEnterTimestamp")
+                        if err != nil {
+                                return nil, fmt.Errorf("couldn't get unit '%s' StartTimeUsec: %s", unit.Name, err)
+                        }
+
+                        unit.startTimeUsec = timestampValue.Value.Value().(uint64)
+                }
+
                 result = append(result, unit)
         }