Move source-tag to toplevel maglev.source-tag config, defaulting to short hostname, v1.1.2

internal/metrics/metrics.go

@@ -21,10 +21,9 @@ import (
 
 // BackendInfo holds the health and config state needed by the collector.
 type BackendInfo struct {
-	Health    *health.Backend
-	Enabled   bool
-	HCName    string // healthcheck name from config
-	SourceTag string // nginx source tag; equals backend name when unset in config
+	Health  *health.Backend
+	Enabled bool
+	HCName  string // healthcheck name from config
 }
 
 // StateSource provides read-only access to the running checker state.
@@ -132,10 +131,11 @@ var (
 // on each scrape. This avoids stale label sets when backends are added or
 // removed by a config reload.
 type Collector struct {
-	src StateSource
-	vpp VPPSource // optional; nil when VPP integration is disabled
+	src       StateSource
+	vpp       VPPSource // optional; nil when VPP integration is disabled
+	sourceTag string
 
-	backendInfo    *prometheus.Desc
+	maglevInfo     *prometheus.Desc
 	backendState   *prometheus.Desc
 	backendHealth  *prometheus.Desc
 	backendEnabled *prometheus.Desc
@@ -154,14 +154,15 @@ type Collector struct {
 // NewCollector creates a Collector backed by the given StateSource. vpp may
 // be nil when VPP integration is disabled; in that case vpp_* metrics are
 // simply not emitted.
-func NewCollector(src StateSource, vpp VPPSource) *Collector {
+func NewCollector(src StateSource, vpp VPPSource, sourceTag string) *Collector {
 	return &Collector{
-		src: src,
-		vpp: vpp,
-		backendInfo: prometheus.NewDesc(
-			"maglev_backend_info",
-			"Static backend metadata. Always 1; metadata is conveyed via labels.",
-			[]string{"backend", "address", "healthcheck", "source_tag"}, nil,
+		src:       src,
+		vpp:       vpp,
+		sourceTag: sourceTag,
+		maglevInfo: prometheus.NewDesc(
+			"maglev_info",
+			"Static maglevd instance metadata. Always 1; metadata is conveyed via labels.",
+			[]string{"source_tag"}, nil,
 		),
 		backendState: prometheus.NewDesc(
 			"maglev_backend_state",
@@ -223,7 +224,7 @@ func NewCollector(src StateSource, vpp VPPSource) *Collector {
 
 // Describe implements prometheus.Collector.
 func (c *Collector) Describe(ch chan<- *prometheus.Desc) {
-	ch <- c.backendInfo
+	ch <- c.maglevInfo
 	ch <- c.backendState
 	ch <- c.backendHealth
 	ch <- c.backendEnabled
@@ -239,6 +240,8 @@ func (c *Collector) Describe(ch chan<- *prometheus.Desc) {
 
 // Collect implements prometheus.Collector.
 func (c *Collector) Collect(ch chan<- prometheus.Metric) {
+	ch <- prometheus.MustNewConstMetric(c.maglevInfo, prometheus.GaugeValue, 1.0, c.sourceTag)
+
 	states := []health.State{
 		health.StateUnknown,
 		health.StateUp,
@@ -255,11 +258,6 @@ func (c *Collector) Collect(ch chan<- prometheus.Metric) {
 		}
 		addr := info.Health.Address.String()
 
-		ch <- prometheus.MustNewConstMetric(
-			c.backendInfo, prometheus.GaugeValue, 1.0,
-			name, addr, info.HCName, info.SourceTag,
-		)
-
 		// One time-series per possible state; the current state is 1, rest 0.
 		for _, s := range states {
 			val := 0.0
@@ -356,8 +354,8 @@ func (c *Collector) Collect(ch chan<- prometheus.Metric) {
 
 // Register registers all metrics with the given registry. vpp may be nil
 // to disable VPP-related metrics.
-func Register(reg prometheus.Registerer, src StateSource, vpp VPPSource) *Collector {
-	coll := NewCollector(src, vpp)
+func Register(reg prometheus.Registerer, src StateSource, vpp VPPSource, sourceTag string) *Collector {
+	coll := NewCollector(src, vpp, sourceTag)
 	reg.MustRegister(coll)
 	reg.MustRegister(ProbeTotal)
 	reg.MustRegister(ProbeDuration)