[BUG] "startup" and "shutdown" events not triggered for mounted APIs

Describe the bug

“startup” and “shutdown” events not triggered for mounted APIs

To Reproduce

from fastapi import FastAPI
from fastapi.testclient import TestClient

app = FastAPI()
subapp = FastAPI()
app.mount("/prefix", subapp)

@app.on_event("startup")
async def startup_event_1() -> None:
    print("startup for", app)

@app.on_event("shutdown")
async def shutdown_event_1() -> None:
    print("shutdown for", app)

@subapp.on_event("startup")
async def startup_event_2() -> None:
    print("startup for", subapp)

@subapp.on_event("shutdown")
async def shutdown_event_2() -> None:
    print("shutdown for", subapp)

with TestClient(app):
    pass

startup/shutdown is triggered for app but not subapp

Expected behavior

Events are emitted in both cases

[leonh]

on_startup and on_shutdown only triggered for the the top level app object. That is the expected behaviour in FastAPI. These hooks are implementation of the ASGI spec provided by Starlette and not strictly part of FastAPI. https://asgi.readthedocs.io/en/latest/specs/lifespan.html

[tiangolo]

Thanks for coming back to close this one! ☕

Sorry for the long delay! 🙈 I wanted to personally address each issue/PR and they piled up through time, but now I’m checking each one in order.