code: public V fetch(K key, Callable<V> callable) throws Exception {
          return locate(key).get(callable);
      }
docs: Fetches an object from the cache. Synchronization at cache level is kept to minimum. The provider is called upon cache miss.
  
  @param key the identity of the object
  @param callable a callable to provide the object upon cache miss
  @return the object requested
  @throws Exception if the provider fails to create a new object