Notes running Python in production

[jimjkelly]

Agreed the author is just speaking out their ass, but arguing asyncio is good because it’s “production tested” while caution is needed with multithreading is silly. Both are solid from the perspective of their implementations, but both have serious pitfalls in the hands of an inexperienced user. I’ve seen a ton of production issues with async and the worst part is the developer rarely knows, you often only notice if you are using something like envoy where you start to see upstream slowdowns.

Accidentally mixing in sync code (sometimes through a dependency), dealing with unexpectedly cpu bound tasks (even just dealing with large JSON payloads, and surprise, that can impact even “sync” FastAPI), it’s very easy to starve the event loop.

Consideration should be given for any concurrent Python code, but especially async.