Code review comment for lp://staging/~mkanat/loggerhead/synchronize-lru_cache

> Well done on tracking down the problem and thanks for the patch. Aren't
> threading problems fun? :-)

  Fun indeed. :-)

> What do you think
> about having a decorator class that provides the synchronized access? E.g.
> changing the cache creation line to be something like ...
>
> graph_cache = ThreadSafeCache(bzrlib.lru_cache.LRUCache(10))
>
> and introducing ThreadSafeCache() as the layer with the RLock?

  I thought about that, and the problem is that it would depend to some degree on implementation details of lru_cache--if the client started using it in different ways, or if the lru_cache implementation changed in some ways, we'd have to start adding locks in different places.

  John has already said that he's not going to make the LRUCache itself thread-safe (see the bug), and the only accesses we make into to it are via this interface, so I think the simplest and most forward-compatible solution is to put the locking in our client code.