FastAPI Others

Logging

Since the app is executed by uvicorn, use its logger.

logger = logging.getLogger('uvicorn')

Middleware

Register middleware to app. Middleware is called by uvicorn.

@app.middleware('http')
async def middleware_example(request: Request, call_next: Callable[[Request], Response]) -> Response: ...

Cross-Origin Resource Sharing (CORS)

CORS middleware is a good example.

origins = [
    'http://localhost:8080',
    'http://localhost',
    'http://localhost-b'
]

app.add_middleware(
    CORSMiddleware,
    allow_origins=origins,  # Allows requests from specific origins
    allow_credentials=True, # Allows credentials in requests (Auth headers, cookies, etc.)
    allow_methods=['*'],    # Allows requests with specific methods
    allow_headers=['*'],    # Allows specific headers in requests
)

There are other fancy middlewares such as uvicorn.ProxyHeadersMiddleware, fastapi.GZipMiddleware, fastapi.TrustedHostMiddleware, fastapi.HTTPSRedirectMiddleware

Background Tasks

You can define background tasks to be run after returning a response. Background Tasks are run by FastAPI. Therefore it can be easily inferred that rules for task functions are identical to path operation or dependency functions. A good example is email notification.

def write_notification(email: str, message=''): ...

@app.post('/users/{user_id}/notification')
async def send_notification(user: Annotated[User, Depends(get_me)], background_tasks: BackgroundTasks):
    background_tasks.add_task(write_notification, user.email, message='Hello world!')

Static Files

You can serve static files from a directory using StaticFiles.

app.mount('/pages', StaticFiles(directory='pages'), name='pages')  # name is FastAPI internal.
app.mount('/scripts', StaticFiles(directory='scripts'), name='scripts')

Lifespan

You can attach async context manager as lifespan event (startup & shutdown). Note that you must attach a function that takes FastAPI as parameter and returns async context manager.

@asynccontextmanager
async def lifespan(app: FastAPI):
    print('start')
    yield
    print('end')

app = FastAPI(lifespan=lifespan)

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