Experiment rate limit in nginx suggested by Claude AI

gistfile1.txt

# Define a shared memory zone to store rate limit state
limit_req_zone $binary_remote_addr zone=req_limit_per_ip:10m rate=10r/s;

# Define a map to store the last failed attempt timestamp
map $remote_addr $last_failed_time {
    volatile;
    default 0;
}

# Define a map to store the retry count
map $remote_addr $retry_count {
    volatile;
    default 0;
}

# Calculate delay based on retry count (2^retry_count - 1)
map $retry_count $delay {
    default 0;
    "0" 0;
    "1" 1;
    "2" 3;
    "3" 7;
    "4" 15;
    "5" 31;
}

server {
    listen 80;
    server_name example.com;

    location / {
        # Check if we need to delay based on previous 429
        if ($last_failed_time) {
            set $wait_time 0;

            # If Retry-After header was present in last response
            if ($http_retry_after) {
                set $wait_time $http_retry_after;
            }
            # Else use exponential backoff
            if ($wait_time = 0) {
                set $wait_time $delay;
            }

            # Calculate if enough time has passed
            set $current_time $time_iso8601;
            if ($current_time - $last_failed_time < $wait_time) {
                return 429 'Too Many Requests\n';
            }
        }

        # Apply rate limiting
        limit_req zone=req_limit_per_ip burst=5 nodelay;

        # Track failed attempts
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header Host $http_host;

        # If request is rate limited (429)
        error_page 429 = @handle_429;

        # Proxy to backend
        proxy_pass http://backend;
    }

    location @handle_429 {
        # Increment retry count
        set $retry_count_new $retry_count;
        if ($retry_count_new != "") {
            set $retry_count_new $retry_count;
            add_header X-Retry-Count $retry_count_new;
        }

        # Store timestamp of this failure
        set $last_failed_time $time_iso8601;

        # Return 429 with appropriate headers
        add_header Retry-After $delay;
        return 429 'Too Many Requests\n';
    }
}