Do some stuff on SIGTERM *before* the app shuts down

[Jakobhenningjensen]

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Example Code

from fastapi import FastAPI
import signal


app = FastAPI()
shutting_down = False

async def do_stuff_before_shutdown():
    shutting_down = True
    # wait 10 seconds before shutting the app down    
    # i.e allowing requests for 10 more seconds
     asyncio.sleep(10) 

@app.get("/health/ready", response_class=PlainTextResponse)
def health_ready():

    text = "OK"
    if shutting_down:
        return PlainTextResponse(text, 425)
    return PlainTextResponse(text, 200)

Description

My FastAPI is run (uvicorn) in a Kubernetes cluster.
I'm trying to gracefully shut it down when the cluster is scaling down.

What I want to do is when I get a sigterm

1. Change "health/ready" to return 425 (such that Kubernetes does not send any more requests to this pod)
2. Allow the app to run for max 30 seconds to finish current tasks before killing it

losely speaking - I want to run a function when SIGTERM is received without "messing" with the sigterm-handler

Step (1) can be done by creating a function and pass it to signal.signal(signal.SIGTERM, ...) but that is being called after the "shutdown" event in the lifespan. I have thought about setting it in the lifespan event, but as far as I understand that happens after the app is shut down - I want to do it before the app shuts down .

Operating System

Linux

Operating System Details

No response

FastAPI Version

0.111.0

Pydantic Version

2.7.4

Python Version

3.11.8

Additional Context