Ratelimit in Fastapi

Question

How to ratelimit API endpoint request in Fastapi application ? I need to ratelimit API call 5 request per second per user and exceeding that limit blocks that particular user for 60 seconds.

In main.py

def get_application() -> FastAPI:
     application = FastAPI(title=PROJECT_NAME, debug=DEBUG, version=VERSION)
     application.add_event_handler(
        "startup", create_start_app_handler(application))
     application.add_event_handler(
        "shutdown", create_stop_app_handler(application))
     return application
app = get_application()

In events.py

def create_start_app_handler(app: FastAPI) -> Callable:  
    async def start_app() -> None:           

        redis = await aioredis.create_redis_pool("redis://localhost:8080")
        FastAPILimiter.init(redis)
    return start_app

In endpoint

@router.post('/user',
             tags=["user"],
             name="user:user", dependencies=[Depends(RateLimiter(times=5, seconds=60))])
***code****

Run from this file test.py.

import uvicorn

from app.main import app

if __name__ == "__main__":
    uvicorn.run("test:app", host="0.0.0.0", port=8000, reload=True)

I edited as above but got following error.

File "****ite-packages\starlette\routing.py", line 526, in lifespan
    async for item in self.lifespan_context(app):
  File "****site-packages\starlette\routing.py", line 467, in default_lifespan
    await self.startup()
  File "****site-packages\starlette\routing.py", line 502, in startup
    await handler()
  File "****app\core\services\events.py", line 15, in start_app
    redis = await aioredis.create_redis_pool("redis://localhost:8080")
  File "****\site-packages\aioredis\commands\__init__.py", line 188, in create_redis_pool
    pool = await create_pool(address, db=db,
  File "****site-packages\aioredis\pool.py", line 58, in create_pool
    await pool._fill_free(override_min=False)
  File "C****\site-packages\aioredis\pool.py", line 383, in _fill_free
    conn = await self._create_new_connection(self._address)
  File "****site-packages\aioredis\connection.py", line 111, in create_connection
    reader, writer = await asyncio.wait_for(open_connection(
  File "****\asyncio\tasks.py", line 455, in wait_for
    return await fut
  File "****\site-packages\aioredis\stream.py", line 23, in open_connection
    transport, _ = await get_event_loop().create_connection(
  File "****\asyncio\base_events.py", line 1033, in create_connection
    raise OSError('Multiple exceptions: {}'.format(
OSError: Multiple exceptions: [Errno 10061] Connect call failed ('::1', 8080, 0, 0), [Errno 10061] Connect call failed ('127.0.0.1', 8080)

Answer 1

Best option is using a library since FastAPI does not provide this functionality out-of-box.

slowapi is great, and easy to use.

You can use ut like this.

from fastapi import FastAPI, Request
from slowapi.errors import RateLimitExceeded
from slowapi import Limiter, _rate_limit_exceeded_handler
from slowapi.util import get_remote_address


limiter = Limiter(key_func=get_remote_address)
app = FastAPI()
app.state.limiter = limiter
app.add_exception_handler(RateLimitExceeded, _rate_limit_exceeded_handler)

@app.get("/home")
@limiter.limit("5/minute")
async def homepage(request: Request):
    return PlainTextResponse("test")

@app.get("/mars")
@limiter.limit("5/minute")
async def homepage(request: Request, response: Response):
    return {"key": "value"}

Answer 2

FastAPI doesn't natively support this, but it's possible with a few libraries such the ones below, but will usually require some sort of database backing(redis, memcached, etc), although slowapi has a memory fallback in case of no database.

• https://pypi.org/project/fastapi-limiter/
• https://pypi.org/project/slowapi/

In order to use fastapi-limiter, as seen in their documentation:

Note: You will need a running Redis for this to work.

import aioredis
import uvicorn
from fastapi import Depends, FastAPI

from fastapi_limiter import FastAPILimiter
from fastapi_limiter.depends import RateLimiter

app = FastAPI()


@app.on_event("startup")
async def startup():
    redis = await aioredis.create_redis_pool("redis://localhost")
    FastAPILimiter.init(redis)


@app.get("/", dependencies=[Depends(RateLimiter(times=2, seconds=5))])
async def index():
    return {"msg": "Hello World"}


if __name__ == "__main__":
    uvicorn.run("main:app", debug=True, reload=True)