Bokeh server: Is it possible to push updates to JS in the middle of a python callback?

[Bryan]

@bjarthur70 You should use a next_tick_callback as described here:

Show loading sign during calculations

I’m not sure the behavior here has ever been defined clearly. It probably should be, and then maintained under test, some day. But as you mention, currently Bokeh state only synchronizes with the browser when the callback ends . If you want to do some update, then alot of blocking work, then another update, you will need to split things up so the first callback completes immediately then schedules the rest of the work to happen after the return. The simplest way is with add_next_tick_callback …

Although there was some question previously, I would say now that the expected behavior is firmly established that changes are only ever synchronized at the end of the function. Now that Bokeh 2.0 will soon be python >= 3.6 only, would like to explore the possibility of allowing await statements in the middle of calbacks for situations like this. But for now, next_tick_callback is the answer.