ModuleNotFoundError when simultaneously running deployed flows using custom image

The problem

Reported in Prefect: ModuleNotFoundError when simultaneously running deployed flows using custom image.

The fix

ModuleNotFoundError when deployed Prefect flows run concurrently from a custom image: root cause was that loadscriptasmodule was not thread-safe (shared 'prefectloader__' module name, sys.path modified without locking, modules evicted from sys.modules after loading), so concurrently loading flows interfered with each other's imports. Fixed in Prefect 3.x: PR #16458 (v3.1.9) added a threading lock and unique module names; PR #17524 (v3.2.14) uses real script filenames as module names and keeps modules in sys.modules. Upgrade to Prefect >= 3.2.14.

In gh:PrefectHQ/prefect#8337 (https://github.com/PrefectHQ/prefect/issues/8337), the reporter ran into this: Reported in Prefect: ModuleNotFoundError when simultaneously running deployed flows using custom image. The verified resolution: ModuleNotFoundError when deployed Prefect flows run concurrently from a custom image: root cause was that loadscriptasmodule was not thread-safe (shared 'prefectloader__' module name, sys.path modified without locking, modules evicted from sys.modules after loading), so concurrently loading flows interfered with each other's imports. Fixed in Prefect 3.x: PR #16458 (v3.1.9) added a threading lock and unique module names; PR #17524 (v3.2.14) uses real script filenames as module names and keeps modules in sys.modules. Upgrade to Prefect >= 3.2.14.