code: func (v *vserver) handleCheckNotification(n *checkNotification) {
  	if !v.enabled {
  		log.Infof("%v: ignoring healthcheck notification %s (vserver disabled)", v, n.description)
  		return
  	}
  
  	check := v.checks[n.key]
  	if check == nil {
  		log.Warningf("%v: unknown check key %v", v, n.key)
  		return
  	}
  
  	transition := (check.status.State != n.status.State)
  	check.description = n.description
  	check.status = n.status
  	if transition {
  		log.Infof("%v: healthcheck %s - %v (%s)", v, n.description, n.status.State, n.status.Message)
  		for _, d := range check.dests {
  			d.updateState()
  		}
  	}
  }
docs: // handleCheckNotification processes a checkNotification, bringing
  // destinations, services, and vservers up or down appropriately.