How to build a Rate Limiter using Redis

Ajeet Raina
Ajeet Raina, Former Developer Growth Manager at Redis

Rate limiting is a mechanism that many developers may have to deal with at some point in their life. It’s useful for a variety of purposes like sharing access to limited resources or limiting the number of requests made to an API endpoint and responding with a 429 status code.

In this tutorial, we will see how to implement Rate Limiting using various programming languages:

Step 1. Pre-requisite#

  • Python
  • Docker
  • Docker Compose

Step 2. Clone the repository#

git clone https://github.com/redis-developer/basic-rate-limiting-demo-python

Step 3. Run docker compose or install redis manually#

docker network create global
docker-compose up -d --build

If you install redis manually open django-backend/configuration folder and copy .env.example to create .env. And provide the values for environment variables - REDIS_HOST: Redis server host - REDIS_PORT: Redis server port - REDIS_DB: Redis server db index - REDIS_PASSWORD: Redis server password

Step 4. Setup and run#

Install python, pip and venv (on mac: https://installpython3.com/mac/)

Use python version: 3.8

python3 -m venv venv
source ./venv/bin/activate
pip3 install -r requirements.txt
python3 manage.py collectstatic
python3 manage.py runserver

Step 5. Accessing the rate limiting app

How it works?#

How the data is stored:#

This app will block connections from a client after surpassing certain amount of requests (default: 10) per time (default: 10 sec) The application will return after each request the following headers. That will let the user know how many requests they have remaining before the run over the limit. On the 10th run server should return an HTTP status code of 429 Too Many Requests

SETNX is short for "SET if Not eXists". It basically sets key to hold string value if key does not exist. In that case, it is equal to SET. When key already holds a value, no operation is performed. New responses are added key-ip as shown below:

 SETNX your_ip:PING limit_amount
 Example: SETNX 10

More information

Set a timeout on key:

 EXPIRE your_ip:PING timeout
 Example: EXPIRE 1000

How the data is accessed:#

Next responses are get bucket:

 GET your_ip:PING
 Example: GET

More information

Next responses are changed bucket:

 DECRBY your_ip:PING amount
 Example: DECRBY 1