Examples

Simple example

from fastapi import FastAPI
from limits.aio.storage import MemoryStorage
from limits.aio.strategies import FixedWindowRateLimiter

from fastlimits import RateLimitingMiddleware, limit

app = FastAPI()

limiter = FixedWindowRateLimiter(storage=MemoryStorage())

app.add_middleware(
    RateLimitingMiddleware,
    strategy=limiter,
)


@limit(app, "5/minute")
@app.get("/")
async def root():
    return {"message": "Hello World"}

Apply limits to all routes (Default limit)

from fastapi import FastAPI
from limits.aio.storage import MemoryStorage
from limits.aio.strategies import FixedWindowRateLimiter

from fastlimits import RateLimitingMiddleware, limit

app = FastAPI()

limiter = FixedWindowRateLimiter(storage=MemoryStorage())

app.add_middleware(
    RateLimitingMiddleware,
    strategy=limiter,
)


@app.get("/")
async def root():
    return {"message": "Hello World"}


limit(app, "5/minute")

Limits on router object

from fastapi import APIRouter, FastAPI
from limits.aio.storage import MemoryStorage
from limits.aio.strategies import FixedWindowRateLimiter

from fastlimits import RateLimitingMiddleware, limit

app = FastAPI()

limiter = FixedWindowRateLimiter(storage=MemoryStorage())

app.add_middleware(
    RateLimitingMiddleware,
    strategy=limiter,
)


@app.get("/")
async def root():
    return {"message": "Hello World"}


router = APIRouter(prefix="/user")


@limit(router, "10/hour")
@router.get("/")
async def get_user(user: User = ...):
    return {"user": ...}


@limit(router, "1/minute")
@router.post("/")
async def create_user(create_user: UserCreateSchema):
    return {"user": create_user}


app.include_router(router)

Limit based on dependencies

examples taken from FastAPI documentation.

from datetime import datetime, timedelta, timezone
from typing import Annotated

import jwt
from fastapi import Depends, FastAPI, HTTPException, status
from fastapi.security import OAuth2PasswordBearer, OAuth2PasswordRequestForm
from jwt.exceptions import InvalidTokenError
from limits.aio.storage import MemoryStorage
from limits.aio.strategies import FixedWindowRateLimiter
from passlib.context import CryptContext
from pydantic import BaseModel

from fastlimits import RateLimitingMiddleware, limit

# to get a string like this run:
# openssl rand -hex 32
SECRET_KEY = "09d25e094faa6ca2556c818166b7a9563b93f7099f6f0f4caa6cf63b88e8d3e7"
ALGORITHM = "HS256"
ACCESS_TOKEN_EXPIRE_MINUTES = 30


fake_users_db = {
    "johndoe": {
        "username": "johndoe",
        "full_name": "John Doe",
        "email": "johndoe@example.com",
        "hashed_password": "$2b$12$EixZaYVK1fsbw1ZfbX3OXePaWxn96p36WQoeG6Lruj3vjPGga31lW",
        "disabled": False,
    }
}


class Token(BaseModel):
    access_token: str
    token_type: str


class TokenData(BaseModel):
    username: str | None = None


class User(BaseModel):
    username: str
    email: str | None = None
    full_name: str | None = None
    disabled: bool | None = None


class UserInDB(User):
    hashed_password: str


pwd_context = CryptContext(schemes=["bcrypt"], deprecated="auto")

oauth2_scheme = OAuth2PasswordBearer(tokenUrl="token")

app = FastAPI()

limiter = FixedWindowRateLimiter(storage=MemoryStorage())

app.add_middleware(
    RateLimitingMiddleware,
    strategy=limiter,
)


def verify_password(plain_password, hashed_password):
    return pwd_context.verify(plain_password, hashed_password)


def get_password_hash(password):
    return pwd_context.hash(password)


def get_user(db, username: str):
    if username in db:
        user_dict = db[username]
        return UserInDB(**user_dict)


def authenticate_user(fake_db, username: str, password: str):
    user = get_user(fake_db, username)
    if not user:
        return False
    if not verify_password(password, user.hashed_password):
        return False
    return user


def create_access_token(data: dict, expires_delta: timedelta | None = None):
    to_encode = data.copy()
    if expires_delta:
        expire = datetime.now(timezone.utc) + expires_delta
    else:
        expire = datetime.now(timezone.utc) + timedelta(minutes=15)
    to_encode.update({"exp": expire})
    encoded_jwt = jwt.encode(to_encode, SECRET_KEY, algorithm=ALGORITHM)
    return encoded_jwt


async def get_current_user(token: Annotated[str, Depends(oauth2_scheme)]):
    credentials_exception = HTTPException(
        status_code=status.HTTP_401_UNAUTHORIZED,
        detail="Could not validate credentials",
        headers={"WWW-Authenticate": "Bearer"},
    )
    try:
        payload = jwt.decode(token, SECRET_KEY, algorithms=[ALGORITHM])
        username: str = payload.get("sub")
        if username is None:
            raise credentials_exception
        token_data = TokenData(username=username)
    except InvalidTokenError:
        raise credentials_exception
    user = get_user(fake_users_db, username=token_data.username)
    if user is None:
        raise credentials_exception
    return user


async def get_current_active_user(
    current_user: Annotated[User, Depends(get_current_user)],
):
    if current_user.disabled:
        raise HTTPException(status_code=400, detail="Inactive user")
    return current_user


async def current_user_key(
    current_user: Annotated[User, Depends(get_current_active_user)],
) -> str:
    return current_user.username


@limit(app, "5/hour")
@app.post("/token")
async def login_for_access_token(
    form_data: Annotated[OAuth2PasswordRequestForm, Depends()],
) -> Token:
    user = authenticate_user(fake_users_db, form_data.username, form_data.password)
    if not user:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="Incorrect username or password",
            headers={"WWW-Authenticate": "Bearer"},
        )
    access_token_expires = timedelta(minutes=ACCESS_TOKEN_EXPIRE_MINUTES)
    access_token = create_access_token(
        data={"sub": user.username}, expires_delta=access_token_expires
    )
    return Token(access_token=access_token, token_type="bearer")


@limit(app, "5/minute", keys=current_user_key)
@app.get("/users/me/", response_model=User)
async def read_users_me(
    current_user: Annotated[User, Depends(get_current_active_user)],
):
    return current_user


@limit(app, "5/minute", keys=current_user_key)
@app.get("/users/me/items/")
async def read_own_items(
    current_user: Annotated[User, Depends(get_current_active_user)],
):
    return [{"item_id": "Foo", "owner": current_user.username}]