metrics

type Counter interface {
	Inc()
	Add(float64)
}

type Gauge interface {
	Inc()
	Dec()
}

type Histogram interface {
	Observe(float64)
}

type HistogramVec interface {
	WithLabelValues(lvs ...string) prometheus.Observer
	Collect(chan<- prometheus.Metric)
	Describe(chan<- *prometheus.Desc)
}