Merge metrics (#8594) (#8637)

Author: zarvd

cmd/cloud-controller-manager/app/controllermanager.go

@@ -325,7 +325,10 @@ func StartHTTPServer(c *cloudcontrollerconfig.CompletedConfig, traceProvider *tr
 	if c.SecureServing != nil {
 		unsecuredMux := genericcontrollermanager.NewBaseHandler(&c.ComponentConfig.Generic.Debugging, healthzHandler)
 
-		unsecuredMux.Handle("/metrics/v2", traceProvider.MetricsHTTPHandler()) // Add metricsv2 endpoint
+		const MetricsPath = "/metrics"
+		unsecuredMux.Unregister(MetricsPath) // Unregisterer handler of legacy registerer
+		unsecuredMux.Handle(MetricsPath, traceProvider.MetricsHTTPHandler())
+		unsecuredMux.Handle("/metrics/v2", traceProvider.MetricsHTTPHandler()) // Will remove in the future after migration
 
 		handler := genericcontrollermanager.BuildHandlerChain(unsecuredMux, &c.Authorization, &c.Authentication)
 		// TODO: handle stoppedCh returned by c.SecureServing.Serve

pkg/trace/provider.go

@@ -31,6 +31,7 @@ import (
 	sdktrace "go.opentelemetry.io/otel/sdk/trace"
 	apitrace "go.opentelemetry.io/otel/trace"
 	tracenoop "go.opentelemetry.io/otel/trace/noop"
+	"k8s.io/component-base/metrics/legacyregistry"
 )
 
 const (
@@ -122,7 +123,10 @@ func (p *Provider) DefaultMeter() apimetric.Meter {
 func (p *Provider) MetricsHTTPHandler() http.Handler {
 	return promhttp.InstrumentMetricHandler(
 		p.prometheusRegistry,
-		promhttp.HandlerFor(p.prometheusRegistry, promhttp.HandlerOpts{}),
+		promhttp.HandlerFor(prometheus.Gatherers{
+			p.prometheusRegistry,
+			legacyregistry.DefaultGatherer, // Merge with the metrics from legacy registerer
+		}, promhttp.HandlerOpts{}),
 	)
 }