Rate-Limiter Challenge

Prerequisites

• Docker
• Go

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General Description

This project implements a configurable Rate Limiter in Go, capable of limiting requests by IP or Access Token, using Redis as a persistence mechanism. It is configured via environment variables or a .env file.

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How It Works

Middleware

• The rate limiter is injected as middleware into the web server.
• It blocks excessive requests based on configured limits per IP or token.

Persistence

• Rate limiter control information is stored in Redis, with support for replacement by other storage strategies, following the Strategy pattern.

Configuration

• Maximum number of requests per second and block time are defined via environment variables.
• Redis is configured to be accessed externally and securely.

HTTP Responses

• When the limit is exceeded:
  • HTTP Status Code: 429
  • Message: You have reached the maximum number of requests or actions allowed within a certain time frame

Available Endpoints

After running the service, the following endpoints will be available:

• GET /: Welcome home page.
• GET /ip?ip=<IP>: Validates and applies limits based on the provided IP address.
• GET /token?token=<TOKEN>: Validates and applies limits based on the provided access token.
• GET /health: Checks the service's health.

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How to Configure

Create a .env file in the root directory of the project and add the following environment variables:

RATE_LIMITER_ADDR=rate-limiter:8080
REDIS_ADDR=redis:6379
REDIS_PASSWORD=
MAX_REQUESTS_PER_SECOND=5
TOKEN_MAX_REQUESTS=10
BLOCK_DURATION_SECONDS=5
TTL_EXPIRATION_SECONDS=5
USE_MEMORY_STORE=false

Variable Descriptions

• RATE_LIMITER_ADDR: Sets the address and port where the server will listen.
• REDIS_ADDR: Redis address to store and retrieve rate limit data.
• REDIS_PASSWORD: Password for Redis authentication, if required.
• MAX_REQUESTS_PER_SECOND: Maximum number of requests per IP per second.
• TOKEN_MAX_REQUESTS: Request limit per token, which overrides the IP limit.
• BLOCK_DURATION_SECONDS: Block time in seconds after exceeding the limit.
• TTL_EXPIRATION_SECONDS: Expiration time for counters in Redis.
• USE_MEMORY_STORE: Defines whether the system uses Redis (false) or in-memory storage (true).

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Running the Project with Docker Compose

Run the following command to start all services:

docker-compose up --build

This will start the following services:

• Redis
• Main application (Rate Limiter)
• Automated tests (unit, integration, and E2E)
• Redis TUI for terminal visualization

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Tests

View Results

• Unit Tests:

  docker logs unit-tests

• Integration Tests:

  docker logs integration-tests

• End-to-End Tests:

  docker logs redis-e2e-tests

Stress Tests

The test was performed using Apache Benchmark:

for i in {1..50}; do
  ab -n 500 -c 25 "http://localhost:8080/ip?ip=192.168.1.$i" >> ip_stress_test.txt 2>&1 &
  ab -n 500 -c 25 -H "API_KEY: token$i" "http://localhost:8080/token" >> token_stress_test.txt 2>&1 &
done

wait

Results are stored in the assets folder.

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TUI Test

After starting Docker Compose, use the command below to open the TUI:

docker attach redis-tui

Redis TUI Screenshot

The interface below displays real-time data: