tkrtmy / fastapi-limiter

A request rate limiter for fastapi

fastapi-limiter

Introduction

FastAPI-Limiter is a rate limiting tool for fastapi routes with lua script.

Requirements

• redis

Install

Just install from pypi

> pip install fastapi-limiter

Quick Start

FastAPI-Limiter is simple to use, which just provide a dependency RateLimiter, the following example allow 2 times request per 5 seconds in route /.

import redis.asyncio as redis
import uvicorn
from contextlib import asynccontextmanager
from fastapi import Depends, FastAPI

from fastapi_limiter import FastAPILimiter
from fastapi_limiter.depends import RateLimiter

@asynccontextmanager
async def lifespan(_: FastAPI):
    redis_connection = redis.from_url("redis://localhost:6379", encoding="utf8")
    await FastAPILimiter.init(redis_connection)
    yield
    await FastAPILimiter.close()

app = FastAPI(lifespan=lifespan)

@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)

Usage

There are some config in FastAPILimiter.init.

redis

The redis instance of aioredis.

prefix

Prefix of redis key.

identifier

Identifier of route limit, default is ip, you can override it such as userid and so on.

async def default_identifier(request: Request):
    forwarded = request.headers.get("X-Forwarded-For")
    if forwarded:
        return forwarded.split(",")[0]
    return request.client.host + ":" + request.scope["path"]

callback

Callback when access is forbidden, default is raise HTTPException with 429 status code.

async def default_callback(request: Request, response: Response, pexpire: int):
    """
    default callback when too many requests
    :param request:
    :param pexpire: The remaining milliseconds
    :param response:
    :return:
    """
    expire = ceil(pexpire / 1000)

    raise HTTPException(
        HTTP_429_TOO_MANY_REQUESTS, "Too Many Requests", headers={"Retry-After": str(expire)}
    )

Multiple limiters

You can use multiple limiters in one route.

@app.get(
    "/multiple",
    dependencies=[
        Depends(RateLimiter(times=1, seconds=5)),
        Depends(RateLimiter(times=2, seconds=15)),
    ],
)
async def multiple():
    return {"msg": "Hello World"}

Not that you should note the dependencies orders, keep lower of result of seconds/times at the first.

Rate limiting within a websocket.

While the above examples work with rest requests, FastAPI also allows easy usage of websockets, which require a slightly different approach.

Because websockets are likely to be long lived, you may want to rate limit in response to data sent over the socket.

You can do this by rate limiting within the body of the websocket handler:

@app.websocket("/ws")
async def websocket_endpoint(websocket: WebSocket):
    await websocket.accept()
    ratelimit = WebSocketRateLimiter(times=1, seconds=5)
    while True:
        try:
            data = await websocket.receive_text()
            await ratelimit(websocket, context_key=data)  # NB: context_key is optional
            await websocket.send_text(f"Hello, world")
        except WebSocketRateLimitException:  # Thrown when rate limit exceeded.
            await websocket.send_text(f"Hello again")

Lua script

The lua script used.

local key = KEYS[1]
local limit = tonumber(ARGV[1])
local expire_time = ARGV[2]

local current = tonumber(redis.call('get', key) or "0")
if current > 0 then
    if current + 1 > limit then
        return redis.call("PTTL", key)
    else
        redis.call("INCR", key)
        return 0
    end
else
    redis.call("SET", key, 1, "px", expire_time)
    return 0
end

License

This project is licensed under the Apache-2.0 License.