func NewLogCache(capacity int, store LogStore) (*LogCache, error) {
	if capacity <= 0 {
		return nil, fmt.Errorf("capacity must be positive")
	}
	c := &LogCache{
		store: store,
		cache: make([]*Log, capacity),
	}
	return c, nil
}
func NewLogCache(capacity int, store LogStore) (*LogCache, error) {
	if capacity <= 0 {
		return nil, fmt.Errorf("capacity must be positive")
	}
	c := &LogCache{
		store: store,
		cache: make([]*Log, capacity),
	}
	return c, nil
}
// NewLogCache is used to create a new LogCache with the
// given capacity and backend store.