rules/alerting.go
func (r *AlertingRule) SetEvaluationDuration(dur time.Duration) {
	r.mtx.Lock()
	defer r.mtx.Unlock()
	r.evaluationDuration = dur
}
func (r *AlertingRule) SetEvaluationDuration(dur time.Duration) {
	r.mtx.Lock()
	defer r.mtx.Unlock()
	r.evaluationDuration = dur
}
// SetEvaluationDuration updates evaluationDuration to the duration it took to evaluate the rule on its last evaluation.