/**
  * Flush all existing items at the server
  *
  * CacheMemcache::truncate() immediately invalidates all existing items.
  * CacheMemcache::truncate() doesn't actually free any resources, it only marks all the items as expired,
  * so occupied memory will be overwitten by new items.
  *
  * @return bool Returns true on success or false on failure.
  */
 function truncate()
 {
     return $this->Memcache->flush();
 }