rules/manager.go
func (g *Group) setEvaluationDuration(dur time.Duration) {
	g.metrics.groupLastDuration.WithLabelValues(groupKey(g.file, g.name)).Set(dur.Seconds())

	g.mtx.Lock()
	defer g.mtx.Unlock()
	g.evaluationDuration = dur
}
func (g *Group) setEvaluationDuration(dur time.Duration) {
	g.metrics.groupLastDuration.WithLabelValues(groupKey(g.file, g.name)).Set(dur.Seconds())

	g.mtx.Lock()
	defer g.mtx.Unlock()
	g.evaluationDuration = dur
}
// setEvaluationDuration sets the time in seconds the last evaluation took.