- async tests are placed in test_pregel_async, not in test_pregel
- to avoid tests placed in wrong file being accidentally skipped i've added the auto-async mark to sync test file
- When using an async entrypoint you can now freely mix and match sync and async tasks with a uniform api (ie all tasks return a sync or async future depending on context)
- Fix issues with scheduling deeply nested tasks (use threadsafe methods to schedule coroutines and create futures)
- both issues are related to the fact that waiters for futures are notified of completion before "done" callbacks are called
- 1st issue manifested as interrupt stream event being emitted before the result of a task that logically finished first (it's in the line above in body of the entrypoint function) -> this is solved by always returning to use code a fresh future chained on the original future, because chaining is done via done callbacks (therefore the chained future will only resolve after done callbacks of the original feature are called)
- 2nd issue mainfested as sometimes (very rarely) the last stream event not being printed before stream() finishes. this is solved by ensuring we only return out of PregelRunner.tick() once all "done" callbacks are called, previously we were approximating this through use of asyncio.sleep(0) / time.sleep(0). The new solution instead waits on a threading/asyncio.Event which will only be set by the last "done" callback to fire
Nuno Campos