Step 1: Install and Configure Nginx

Before configuring rate limiting, make sure Nginx is installed on your system. You can install Nginx on most Linux distributions with the following command:

sudo apt install nginx -y

Start and enable Nginx to run at boot:

sudo systemctl start nginx
sudo systemctl enable nginx

Step 2: Understand Nginx Rate Limiting Directives

Nginx provides two key directives for rate limiting:

• limit_req_zone: Defines the rate-limiting zone and request rate.
• limit_req: Applies rate limiting to a specific location or server block.

These directives are used in combination to specify the rate of requests that a client can send.

Step 3: Define a Rate-Limiting Zone

First, you need to define a shared memory zone that will track the number of requests made by each IP address. Open the Nginx configuration file:

sudo nano /etc/nginx/nginx.conf

Add the following configuration to define a rate-limiting zone:

http {
    limit_req_zone $binary_remote_addr zone=myzone:10m rate=5r/s;
    
    ...
}

In this example, we create a zone called "myzone" with 10MB of memory, and limit the rate to 5 requests per second (5r/s) for each IP address.

Step 4: Apply Rate Limiting to a Specific Location

After defining the rate-limiting zone, you can apply it to specific locations or server blocks. For example, to limit requests to the entire website, modify the server block:

server {
    listen 80;
    server_name yourdomain.com;

    location / {
        limit_req zone=myzone burst=10 nodelay;
        ...
    }

    ...
}

The burst parameter allows a client to exceed the rate limit by 10 requests in a burst. The nodelay option ensures that requests exceeding the rate limit are dropped immediately, rather than being queued.

Step 5: Test the Rate Limiting Configuration

After configuring rate limiting, reload the Nginx configuration to apply the changes:

sudo nginx -t
sudo systemctl reload nginx

You can test the rate-limiting setup using tools like curl or Apache Benchmark (ab). For example, use the following command to send multiple requests and observe the rate limiting in action:

ab -n 50 -c 10 http://yourdomain.com/

Step 6: Logging Rate-Limited Requests (Optional)

Nginx allows you to log rate-limited requests for monitoring purposes. You can include this configuration in your nginx.conf file:

log_format rate_limited '$remote_addr - $server_name - $request_uri - $status - $body_bytes_sent - $request_time';
access_log /var/log/nginx/rate_limited.log rate_limited;

This will create a custom log format for tracking rate-limited requests.