greenlet local storage on greenlet 0.4.0

Greenlet 0.4.0 brought an interesting new feature: an instance dictionary on each greenlet object, which makes it a lot simpler to implement greenlet local storage. Here is how greenlet local storage is currently implemented in Eventlet and in Gevent.

As it can be seen, the implementation is not particularly straightforward, mainly due to the fact that the actual information needs to be stored in a separate entity and mapped to each greenlet.

Thanks to the instance dictionary added in 0.4.0, we can use some attribute in it to keep the locally stored objects. The plan is to use a dictionary called __local_dict__ and store the greenlet local attributes there. Here is how it looks like:

Hope it’s of use.