FastAPI+Uvicorn Startup Event Handling Long-Running Functions

[Well2333]

I'm using FastAPI with Uvicorn, and I'm encountering an issue with long-running asynchronous functions in the startup event (@app.on_event("startup")). These functions prevent the program from being interrupted gracefully (e.g., via Ctrl+C), which is critical for my use case where the startup phase includes potentially lengthy operations like setting up database connections or external API calls. This behavior might be related to FastAPI's underlying framework, starlette.

import asyncio
from fastapi import FastAPI
import uvicorn

app = FastAPI()

@app.on_event("startup")
async def startup_event():
    print("startup")
    await asyncio.sleep(5)  # Simulating a long-running task
    print("startup complete")

if __name__ == "__main__":
    uvicorn.run(app, host="127.0.0.1", port=8000)

I would like the application to remain responsive to interrupt signals even during the execution of long-running startup tasks. Ideally, it should be possible to stop the server gracefully at any point, including during the startup phase.

I am looking for suggestions or solutions that could help in making the startup_event in FastAPI (possibly influenced by starlette) interruptible. This might include insights into starlette's handling of asynchronous tasks, custom signal handling, event loop management, or any architectural changes that can improve responsiveness to interrupts during startup.