Metaclass to make all methods of a class thread-safe

[Michele Simionato]

Irmen de Jong <irmen at -nospam-remove-this-xs4all.nl> wrote in message news:<415728eb$0$78753$e4fe514c at news.xs4all.nl>...
> Hi,
> I've developed the Metaclass below, because I needed a way
> to make a bunch of classes thread-safe.
> I didn't want to change every method of the class by adding
> lock.aqcuire()..lock.release() around the existing code.
> So I made a metaclass that essentially replaces every method
> of a class with a 'wrapper' method, that does the locking,
> invocation, unlocking.
> 
> Is this the right approach? It seems to work fine. But I have
> very little experience with metaclass programming, so I'd like
> to hear some feedback.
> 
> Thanks !!
> 
> --Irmen de Jong.

Well, it looks okay, but consider the following:

1. you have a (metaclass) static method and a (metaclass) classmethod
   which could be replaced by simple functions external to the metaclass;
   this would make the code much easier to read and to understand; I don't
   buy the argument that they should logically stay in the metaclass, it
   is enough if they stay in the same module of the metaclass, not inside it;

2. the metaclass will automagically wrap even methods of subclasses, without
   you knowing it; consider using a naming convention (es. only methods
   starting with "t_" are magically wrapped); if still
   you want the magic, consider defining a name convention such as methods
   starting with a given prefix are NOT magically wrapped; 

4. built-in methods and all the objects which are non instances of FunctionType
   will be not wrapped; you may want this or not;
    
5. consider using decorators to wrap the methods you want to be
   thread safe: they a more esplicit and easier to understand solution;
   also in this way you will avoid the (possible) issue of metaclass 
   conflicts.

6. However, if you want to enhance a code which is already written
   with a minimal change of the source code, the metaclass is the 
   simplest solution indeed.

Just my 0.02c,

           Michele Simionato