egress_selector.go: Add a dial starts metric.

Emit this metric before any potentially blocking dial work.

staging/src/k8s.io/apiserver/pkg/server/egressselector/egress_selector.go

@@ -243,6 +243,7 @@ func (d *dialerCreator) createDialer() utilnet.DialFunc {
 		ctx, span := tracing.Start(ctx, fmt.Sprintf("Proxy via %s protocol over %s", d.options.protocol, d.options.transport), attribute.String("address", addr))
 		defer span.End(500 * time.Millisecond)
 		start := egressmetrics.Metrics.Clock().Now()
+		egressmetrics.Metrics.ObserveDialStart(d.options.protocol, d.options.transport)
 		proxier, err := d.connector.connect(ctx)
 		if err != nil {
 			egressmetrics.Metrics.ObserveDialFailure(d.options.protocol, d.options.transport, egressmetrics.StageConnect)

staging/src/k8s.io/apiserver/pkg/server/egressselector/egress_selector_test.go

@@ -201,6 +201,16 @@ func TestMetrics(t *testing.T) {
 		metrics      []string
 		want         string
 	}{
+		"connect to proxy server start": {
+			connectorErr: true,
+			proxierErr:   true,
+			metrics:      []string{"apiserver_egress_dialer_dial_start_total"},
+			want: `
+	# HELP apiserver_egress_dialer_dial_start_total [ALPHA] Dial starts, labeled by the protocol (http-connect or grpc) and transport (tcp or uds).
+	# TYPE apiserver_egress_dialer_dial_start_total counter
+	apiserver_egress_dialer_dial_start_total{protocol="fake_protocol",transport="fake_transport"} 1
+`,
+		},
 		"connect to proxy server error": {
 			connectorErr: true,
 			proxierErr:   false,

staging/src/k8s.io/apiserver/pkg/server/egressselector/metrics/metrics.go

@@ -53,12 +53,24 @@ var (
 // DialMetrics instruments dials to proxy server with prometheus metrics.
 type DialMetrics struct {
 	clock     clock.Clock
+	starts    *metrics.CounterVec
 	latencies *metrics.HistogramVec
 	failures  *metrics.CounterVec
 }
 
 // newDialMetrics create a new DialMetrics, configured with default metric names.
 func newDialMetrics() *DialMetrics {
+	starts := metrics.NewCounterVec(
+		&metrics.CounterOpts{
+			Namespace:      namespace,
+			Subsystem:      subsystem,
+			Name:           "dial_start_total",
+			Help:           "Dial starts, labeled by the protocol (http-connect or grpc) and transport (tcp or uds).",
+			StabilityLevel: metrics.ALPHA,
+		},
+		[]string{"protocol", "transport"},
+	)
+
 	latencies := metrics.NewHistogramVec(
 		&metrics.HistogramOpts{
 			Namespace:      namespace,
@@ -82,9 +94,10 @@ func newDialMetrics() *DialMetrics {
 		[]string{"protocol", "transport", "stage"},
 	)
 
+	legacyregistry.MustRegister(starts)
 	legacyregistry.MustRegister(latencies)
 	legacyregistry.MustRegister(failures)
-	return &DialMetrics{latencies: latencies, failures: failures, clock: clock.RealClock{}}
+	return &DialMetrics{starts: starts, latencies: latencies, failures: failures, clock: clock.RealClock{}}
 }
 
 // Clock returns the clock.
@@ -99,10 +112,16 @@ func (m *DialMetrics) SetClock(c clock.Clock) {
 
 // Reset resets the metrics.
 func (m *DialMetrics) Reset() {
+	m.starts.Reset()
 	m.latencies.Reset()
 	m.failures.Reset()
 }
 
+// ObserveDialStart records the start of a dial attempt, labeled by protocol, transport.
+func (m *DialMetrics) ObserveDialStart(protocol, transport string) {
+	m.starts.WithLabelValues(protocol, transport).Inc()
+}
+
 // ObserveDialLatency records the latency of a dial, labeled by protocol, transport.
 func (m *DialMetrics) ObserveDialLatency(elapsed time.Duration, protocol, transport string) {
 	m.latencies.WithLabelValues(protocol, transport).Observe(elapsed.Seconds())