Act-Ratelimit

Introduction

Act-Ratelimit is a rate limiting tool for fastapi.
It is a fork of fastapi-limiter with support for multiple Datastores and different Ratelimit strategies.

Requirements

• fastapi

Additional Requirements

• redis if you want to use the redis-backend
• valkey if you want to use the valkey-backend

Install

Just install from pypi

pip install act-ratelimit

You can also install the additional requirements

pip install act-ratelimit[redis]
pip install act-ratelimit[valkey]

Quick Start

Act-Ratelimit is simple to use, you need to initialize it with your preferred backend and then use the RateLimiter dependency in your routes.

import redis.asyncio as redis
from contextlib import asynccontextmanager

from act_ratelimit import ACTRatelimit
from act_ratelimit.depends import RateLimiter
from act_ratelimit.backends import RedisBackend


@asynccontextmanager
async def lifespan(_: FastAPI):
    redis_backend = RedisBackend(
        redis.from_url("redis://localhost:6379", encoding="utf8"), prefix="act-ratelimit-example"
    )
    await ACTRatelimit.init(redis_backend)
    yield
    await ACTRatelimit.close()


app = FastAPI(lifespan=lifespan)


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

[!NOTE] For people coming from fastapi-limiter, the FastAPILimiter.init method has changed. It now takes a backend instance instead of a redis instance.

Usage

You will first need to initialize the ACTRatelimit with a backend instance.

Other possible parameters are:

• identifier - The identifier of the rate limit, default is ip.
• callback - The callback when the rate limit is exceeded.
• strategy - The strategy to use for the rate limit, default is FIXED_WINDOW.

Backend

There are currently two backends pre-implemented, RedisBackend and ValkeyBackend.

RedisBackend uses the redis library to interact with a redis instance.
ValkeyBackend uses the valkey library to interact with a valkey instance.

You can also implement your own backend by inheriting from the BaseBackend class.

from act_ratelimit.backends import BaseBackend
from act_ratelimit.constants import RateLimitStrategy

class MyBackend(BaseBackend):
    
    async def check(self, key: str, times: int, limit: int, strategy: RateLimitStrategy) -> int:
        """Check if a key has hit the rate limit.
    
        This method should return the time in milliseconds until the rate limit resets.
        If the rate limit has not been hit, it should return 0.
    
        Args:
            key: The key to check.
            times: The number of times the key has to be hit to trigger the rate limit.
            limit: How long the rate limit should last in milliseconds.
        """
        raise NotImplementedError

    async def close(self) -> None:
        """Close the connection to the backend."""
        raise NotImplementedError

Strategies

There are currently three strategies available, FIXED_WINDOW, SLIDING_WINDOW and FIXED_WINDOW_ELASTIC.

[!NOTE] These Strategies need to be implemented in the backend. If you are using a custom backend, you will need to implement these strategies.

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:
    """

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

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")

License

This fork contains modifications by Act-App licensed under MIT License. The original project remains under the Apache-2.0 License.