func (s *Service) BlockDelay(epochSlot uint, delay time.Duration) {
	s.blockReceiptDelay.WithLabelValues(fmt.Sprintf("%d", epochSlot)).Observe(delay.Seconds())
}
BlockDelay provides the delay between the start of a slot and vouch receiving its block.
package prometheus
import (
	"fmt"
	"time"
	"github.com/prometheus/client_golang/prometheus"
)
func (s *Service) setupControllerMetrics() error {
	s.epochsProcessed = prometheus.NewCounter(prometheus.CounterOpts{
		Namespace: "vouch",
		Name:      "epochs_processed_total",
		Help:      "The number of epochs vouch has processed.",
	})
	if err := prometheus.Register(s.epochsProcessed); err != nil {
		return err
	}
	s.blockReceiptDelay =
		prometheus.NewHistogramVec(prometheus.HistogramOpts{
			Namespace: "vouch",
			Name:      "block_receipt_delay_seconds",
			Help:      "The delay between the start of a slot and the time vouch receives it.",
			Buckets: []float64{
				0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0,
				1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0,
				2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0,
				3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0,
				4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0,
				5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6.0,
				6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, 7.0,
				7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, 8.0,
				8.1, 8.2, 8.3, 8.4, 8.5, 8.6, 8.7, 8.8, 8.9, 9.0,
				9.1, 9.2, 9.3, 9.4, 9.5, 9.6, 9.7, 9.8, 9.9, 10.0,
				10.1, 10.2, 10.3, 10.4, 10.5, 10.6, 10.7, 10.8, 10.9, 11.0,
				11.1, 11.2, 11.3, 11.4, 11.5, 11.6, 11.7, 11.8, 11.9, 12.0,
			},
		}, []string{"epoch_slot"})
	return prometheus.Register(s.blockReceiptDelay)
}
func (s *Service) NewEpoch() {
	s.epochsProcessed.Inc()
}