go.d/prometheus: add label_prefix config option (netdata#18559)

src/go/plugin/go.d/modules/prometheus/charts.go

@@ -41,7 +41,7 @@ func (p *Prometheus) addGaugeChart(id, name, help string, labels labels.Labels)
 	for _, lbl := range labels {
 		chart.Labels = append(chart.Labels,
 			module.Label{
-				Key:   lbl.Name,
+				Key:   p.labelName(lbl.Name),
 				Value: apostropheReplacer.Replace(lbl.Value),
 			},
 		)
@@ -84,7 +84,7 @@ func (p *Prometheus) addCounterChart(id, name, help string, labels labels.Labels
 	for _, lbl := range labels {
 		chart.Labels = append(chart.Labels,
 			module.Label{
-				Key:   lbl.Name,
+				Key:   p.labelName(lbl.Name),
 				Value: apostropheReplacer.Replace(lbl.Value),
 			},
 		)
@@ -154,7 +154,7 @@ func (p *Prometheus) addSummaryCharts(id, name, help string, labels labels.Label
 	for _, chart := range charts {
 		for _, lbl := range labels {
 			chart.Labels = append(chart.Labels, module.Label{
-				Key:   lbl.Name,
+				Key:   p.labelName(lbl.Name),
 				Value: apostropheReplacer.Replace(lbl.Value),
 			})
 		}
@@ -222,7 +222,7 @@ func (p *Prometheus) addHistogramCharts(id, name, help string, labels labels.Lab
 	for _, chart := range charts {
 		for _, lbl := range labels {
 			chart.Labels = append(chart.Labels, module.Label{
-				Key:   lbl.Name,
+				Key:   p.labelName(lbl.Name),
 				Value: apostropheReplacer.Replace(lbl.Value),
 			})
 		}
@@ -241,6 +241,13 @@ func (p *Prometheus) application() string {
 	return p.Name
 }
 
+func (p *Prometheus) labelName(lblName string) string {
+	if p.LabelPrefix == "" {
+		return lblName
+	}
+	return p.LabelPrefix + "_" + lblName
+}
+
 func getChartTitle(name, help string) string {
 	if help == "" {
 		return fmt.Sprintf("Metric \"%s\"", name)

src/go/plugin/go.d/modules/prometheus/config_schema.json

@@ -34,6 +34,11 @@
         "description": "If an endpoint does not return at least one metric with the specified prefix, the data is not processed.",
         "type": "string"
       },
+      "label_prefix": {
+        "title": "Label prefix",
+        "description": "An optional prefix that will be added to all labels of all charts. If set, the label names will be automatically formatted as `prefix_name` (the prefix followed by an underscore and the original name).",
+        "type": "string"
+      },
       "app": {
         "title": "Application",
         "description": "If set, this value will be used in the chart context as 'prometheus.{app}.{metric_name}'.",

src/go/plugin/go.d/modules/prometheus/metadata.yaml

@@ -113,6 +113,10 @@ modules:
               description: Time series per metric (metric name) limit. Metrics with number of time series > limit are skipped.
               default_value: 200
               required: false
+            - name: label_prefix
+              description: "An optional prefix that will be added to all labels of all charts. If set, the label names will be automatically formatted as `prefix_name` (the prefix followed by an underscore and the original name)."
+              default_value: ""
+              required: false
             - name: timeout
               description: HTTP request timeout.
               default_value: 10

src/go/plugin/go.d/modules/prometheus/prometheus.go

@@ -50,6 +50,7 @@ type Config struct {
 	web.HTTPConfig  `yaml:",inline" json:""`
 	Name            string        `yaml:"name,omitempty" json:"name"`
 	Application     string        `yaml:"app,omitempty" json:"app"`
+	LabelPrefix     string        `yaml:"label_prefix,omitempty" json:"label_prefix"`
 	BearerTokenFile string        `yaml:"bearer_token_file,omitempty" json:"bearer_token_file"`
 	Selector        selector.Expr `yaml:"selector,omitempty" json:"selector"`
 	ExpectedPrefix  string        `yaml:"expected_prefix,omitempty" json:"expected_prefix"`

src/go/plugin/go.d/modules/prometheus/testdata/config.json

@@ -19,6 +19,7 @@
   "tls_skip_verify": true,
   "name": "ok",
   "app": "ok",
+  "label_prefix": "ok",
   "bearer_token_file": "ok",
   "selector": {
     "allow": [

src/go/plugin/go.d/modules/prometheus/testdata/config.yaml

@@ -17,6 +17,7 @@ tls_key: "ok"
 tls_skip_verify: yes
 name: "ok"
 app: "ok"
+label_prefix: "ok"
 bearer_token_file: "ok"
 selector:
   allow: