sync: create a snapshot after some limit no matter what (no debouncing)

[williamstein]

If there are sustained patches being made then we can get in a situation where no snapshot ever gets made, which breaks things.

[williamstein]

I.e., have a limit of at most 2 patches per second.

Here is an example to illustrate the problem:

import sys, time
for i in range(100):
    sys.stdout.write("%s"%i)
    sys.stdout.flush()
    time.sleep(0.1)

Yes, this will make output like this much less smooth. But that's fine and what something ipywidgets addresses properly.

[williamstein]

Probably a better fix would be enforcing some backend hard limits to never get in this situation?

[williamstein]

I'm going to close this -- the right fix is to make all clients not create too many patches, then make the backend hub reject excess patches anyways (to avoid issues with malicious clients).