I think this explains what is going on:
I had a Genie-related issue for weeks now - and I wasn’t able to track it down until yesterday when I tried to help solving this issue. I assumed that the complexity of my project and the difficulty to write proper tests to catch the responsivity issue was on me - and I was in the process of refactoring stuff.
~10 hours later - trying to invalidate my conclusions (I initially assumed that it is just about communication between tasks - so I did invalidate some) I arrived at an even more upsetting conclusion: you cannot do proper (or predictible/interactive) multithreading in Julia if your project involves medium-heavy work on main and your tasks are somehow using libuv. Just run my HTTP.jl MWE from an above post.
So - there is hard to say how many Julia packages are poisoned in this way:
- It is not straightforward what tests should be run to determine if there is an issue.
- If you want to go into source code for anything you use, it is pretty time-consuming (the language users should not need to do such things).
- Many toy examples from documentation will not reveal the issue.
For me, it is just incredible that this is happening. Imagine not being able to properly run a server on a different thread because its responsivity will be conditioned on not doing anything significant on the main thread.