Add collector for hostname information

This can be useful for building grafana dashboards with dropdowns for multiple hosts
Or for managed instances of Prometheus where the user is not able to add labels via config

collector/cs.go

@@ -18,6 +18,7 @@ func init() {
 type CSCollector struct {
 	PhysicalMemoryBytes *prometheus.Desc
 	LogicalProcessors   *prometheus.Desc
+	Hostname            *prometheus.Desc
 }
 
 // NewCSCollector ...
@@ -37,6 +38,15 @@ func NewCSCollector() (Collector, error) {
 			nil,
 			nil,
 		),
+		Hostname: prometheus.NewDesc(
+			prometheus.BuildFQName(Namespace, subsystem, "hostname"),
+			"Labeled system hostname information as provided by ComputerSystem.DNSHostName and ComputerSystem.Domain",
+			[]string{
+				"hostname",
+				"domain",
+				"fqdn"},
+			nil,
+		),
 	}, nil
 }
 
@@ -55,6 +65,9 @@ func (c *CSCollector) Collect(ctx *ScrapeContext, ch chan<- prometheus.Metric) e
 type Win32_ComputerSystem struct {
 	NumberOfLogicalProcessors uint32
 	TotalPhysicalMemory       uint64
+	DNSHostname               string
+	Domain                    string
+	Workgroup                 string
 }
 
 func (c *CSCollector) collect(ch chan<- prometheus.Metric) (*prometheus.Desc, error) {
@@ -79,5 +92,21 @@ func (c *CSCollector) collect(ch chan<- prometheus.Metric) (*prometheus.Desc, er
 		float64(dst[0].TotalPhysicalMemory),
 	)
 
+	var fqdn string
+	if dst[0].Domain != dst[0].Workgroup {
+		fqdn = dst[0].DNSHostname + "." + dst[0].Domain
+	} else {
+		fqdn = dst[0].DNSHostname
+	}
+
+	ch <- prometheus.MustNewConstMetric(
+		c.Hostname,
+		prometheus.GaugeValue,
+		1.0,
+		dst[0].DNSHostname,
+		dst[0].Domain,
+		fqdn,
+	)
+
 	return nil, nil
 }