Memory Leak in Client

[garvenlee]

The implementation of Client.waiters is a defaultdict(set), each waiter will only be poped out from the set when it completes, while the underlying set will still occupy memory. Similarly, within the _listener task, after a frame is read, defaultdict creates a set internally when calling waiters[key] with the key not in waiters, which is useless but has not been cleaned up.

[garvenlee]

And why needs a set factory in defaultdict ?

[qweeze]

Thanks @garvenlee! Yep, that's a bug. Submitted a fix #129