fastapi_rlr 0.1.0

FastAPI middleware for IP-based rate limiting using Redis, with configurable request limits and time windows.

FastAPI Rate Limiter Middleware

Project Description

This project implements a Rate Limiting Middleware for a FastAPI application. The middleware restricts how many requests a client (identified by IP address) can make within a defined time window. It helps protect your API from abuse, excessive traffic, and denial-of-service (DoS) attacks by throttling requests at the middleware level before they reach the main application logic.

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Key Features

• 🔒 Per-IP Rate Limiting: Limits each unique IP address to a fixed number of requests within a given time window.
• ⏱️ Configurable Limits: Easily set the number of allowed requests and time window (e.g., 5 requests per 60 seconds).
• 🧠 Smart Storage with Redis: Uses Redis to efficiently store and manage request counters with TTL (time-to-live).
• 📉 Fail-Open Strategy: If Redis is unavailable, the middleware gracefully lets requests through to avoid blocking legitimate users.
• 🔄 Auto Reset: Counters reset automatically after the time window expires.
• 📦 Reusable Component: Designed as a plug-and-play middleware class for any FastAPI project.

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How It Works

1. When a request comes in, the middleware checks the client’s IP address.
2. It creates or updates a Redis key that tracks the number of requests from that IP.
3. If the request count exceeds the allowed limit:
   • The request is rejected with HTTP 429 Too Many Requests.
   • A message is returned including the retry_after_seconds field indicating how long to wait before retrying.
4. If under the limit, the request proceeds normally to the API endpoint.

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Tech Stack

Technology	Purpose
FastAPI	Web framework for building APIs
Redis	In-memory data store for counters
Uvicorn	ASGI server to run the FastAPI app
Starlette	Base for FastAPI and middleware

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Example

# main.py
from fastapi import FastAPI
from fastapi_rlr import RateLimiterMiddleware

app = FastAPI()

# Add middleware with Redis URL
app.add_middleware(
    RateLimiterMiddleware,
    redis_url="redis://localhost:6379",  # Adjust to your Redis config
    max_requests=5,
    window_seconds=60
)

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