How to run a func only once at a server shutdown？

[mattholy]

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Example Code

@app.on_event()

Description

When use '@app.on_event()' on a multiple-worker server, I find that this handler will be called many times.
I wonder if there is any thing be called only once at a server shutdown?

Operating System

Windows

Operating System Details

Windows 11

FastAPI Version

0.70.0

Python Version

3.9

Additional Context

No response

[insomnes]

I bet, in this situation you should use some external locking mechanism or consider usage shutdown hooks of your web-server process manager. Like on_exit in Gunicorn

[panla]

try using the thread level singleton mode

[flapili]

are you sure it's the scope of fastapi / uvicorn or even gunicorn to do that ? sound like an XY problem to me

[raphaelauv]

@insomnes is right, this is not a fastAPI question.

The answer is going to depend how you run fastAPI

import time
import uvicorn
async def app(scope, receive, send):
    pass
if __name__ == "__main__":
    uvicorn.run("toto:app", host="127.0.0.1", port=5000, log_level="info", workers=2)
    time.sleep(2)
    print("LAST STEP")

INFO:     Uvicorn running on http://127.0.0.1:5000 (Press CTRL+C to quit)
INFO:     Started parent process [1566165]
INFO:     Started server process [1566169]
INFO:     Waiting for application startup.
INFO:     Application startup complete.
INFO:     Started server process [1566168]
INFO:     Waiting for application startup.
INFO:     Application startup complete.
INFO:     Shutting down
INFO:     Shutting down
INFO:     Waiting for application shutdown.
INFO:     Application shutdown complete.
INFO:     Finished server process [1566169]
INFO:     Finished server process [1566168]
INFO:     Stopping parent process [1566165]
LAST STEP

Process finished with exit code 0

I think you can close this issue @mattholy , thank you