Nuitka+fastapi+uvicorn=«multiprocessing/resource_tracker.py:96: UserWarning: resource_tracker: process died unexpectedly, relaunching»

Consider following minimal sample project used FastAPI with uvicorn, based on pipenv for fast reproduceability. https://github.com/belonesox/fastapi-unicorn-nuitka-troubles

• Checkout it.

• test1.py demo service with 1 worker

• test2.py demo run service with 2 workers

• sh reproduce-me.sh — compile both of them

• pure_python_ok.sh — successfully run using raw python (both 1worker and 2worker versions).

INFO:     Uvicorn running on http://0.0.0.0:8040 (Press CTRL+C to quit)
INFO:     Started parent process [1138946]
INFO:     Started server process [1138961]
INFO:     Waiting for application startup.
INFO:     Application startup complete.
INFO:     Started server process [1138962]
INFO:     Waiting for application startup.
INFO:     Application startup complete.

To check that service is working, just open http://localhost:8040/docs

• compiled_1worker_ok.sh — run compiled nuitka version with 1 worker, OK INFO: Started server process [1139332] INFO: Waiting for application startup. INFO: Application startup complete. INFO: Uvicorn running on http://0.0.0.0:8040 (Press CTRL+C to quit)
• compiled_2worker_bad.sh — run compiled nuitka version with 2 worker, failed with test2.dist/multiprocessing/resource_tracker.py:96: UserWarning: resource_tracker: process died unexpectedly, relaunching. Some resources might leak.

[belonesox]

Confirm that. Works for me on

Fedora           34 
Nuitka            0.8.2
uvicorn           0.17.6

even with 100 workers.

[kayhayen]

This just worked for me with 2 workers. Probably a multiprocessing improvement fixed that some time ago.