app/app.go
func (app *App) available() bool {
	units, err := app.Units()
	if err != nil {
		return false
	}
	for _, unit := range units {
		if unit.Available() {
			return true
		}
	}
	return false
}
func (app *App) available() bool {
	units, err := app.Units()
	if err != nil {
		return false
	}
	for _, unit := range units {
		if unit.Available() {
			return true
		}
	}
	return false
}
// available returns true if at least one of N units is started or unreachable.