FrontendMetrics: Adds new backend api that frontend can use to push frontend measurements and counters to prometheus (#32593)

* FrontendMetrics: Adds new backend api that frontend can use to push frontend measurements and counters to prometheus

* FrontendMetrics: Adds new backend api that frontend can use to push frontend measurements and counters to prometheus

* Fix naming

* change to histogram

* Fixed go lint

pkg/infra/metrics/frontendmetrics.go

@@ -0,0 +1,43 @@
+package metrics
+
+import "github.com/prometheus/client_golang/prometheus"
+
+// PostPostFrontendMetricsCommand sent by frontend to record frontend metrics
+type PostFrontendMetricsCommand struct {
+	Events []FrontendMetricEvent `json:"events"`
+}
+
+// FrontendMetricEvent a single metric measurement event
+type FrontendMetricEvent struct {
+	Name  string  `json:"name"`
+	Value float64 `json:"value"`
+}
+
+// FrontendMetricsRecorder handles the recording of the event, ie passes it to a prometheus metric
+type FrontendMetricsRecorder func(event FrontendMetricEvent)
+
+// FrontendMetrics contains all the valid frontend metrics and a handler function for recording events
+var FrontendMetrics map[string]FrontendMetricsRecorder = map[string]FrontendMetricsRecorder{}
+
+func registerFrontendHistogram(name string, help string) {
+	defBuckets := []float64{.1, .25, .5, 1, 1.5, 2, 5, 10, 20, 40}
+
+	histogram := prometheus.NewHistogram(prometheus.HistogramOpts{
+		Name:      name,
+		Help:      help,
+		Buckets:   defBuckets,
+		Namespace: ExporterName,
+	})
+
+	FrontendMetrics[name] = func(event FrontendMetricEvent) {
+		histogram.Observe(event.Value)
+	}
+
+	prometheus.MustRegister(histogram)
+}
+
+func initFrontendMetrics() {
+	registerFrontendHistogram("frontend_boot_load_time_seconds", "Frontend boot time measurement")
+	registerFrontendHistogram("frontend_boot_first_paint_time_seconds", "Frontend boot first paint")
+	registerFrontendHistogram("frontend_boot_js_done_time_seconds", "Frontend boot initial js load")
+}

pkg/infra/metrics/service.go

@@ -22,6 +22,7 @@ func (lw *logWrapper) Println(v ...interface{}) {
 func init() {
 	registry.RegisterService(&InternalMetricsService{})
 	initMetricVars()
+	initFrontendMetrics()
 }
 
 type InternalMetricsService struct {