metrics

type Counter interface {
	Inc()
	Add(float64) // Only positive
}

type CounterVec interface {
	WithLabelValues(lvs ...string) Counter
}

type Creator interface {
	Counter() Counter
	CounterVec(labelNames []string) CounterVec
	Gauge() Gauge
	Histogram(buckets []float64) Histogram

	// opts cannot be nil, use empty summary instance
	Summary(opts SummaryOpts) Summary
}

type Gauge interface {
	Set(float64) // Introduced discontinuity
	Inc()
	Dec()
	Add(float64)
	Sub(float64)
}

type Histogram interface {
	Observe(float64) // Adds observation to Histogram
}

type InternalNew func(string, string) Creator

type Summary interface {
	Observe(float64) // Adds observation to Summary
}

type SummaryOpts struct {
	Objectives map[float64]float64
	MaxAge     time.Duration
	AgeBuckets uint32
	BufCap     uint32
}