How to use rate limiting with Symfony’s HTTP kernel?

Rate limiting in Symfony's HTTP kernel can be accomplished by using middleware to control the number of requests a user can send within a certain time period. Here is how you can implement rate limiting with Symfony's HTTP kernel:

Create a new middleware class that will handle rate limiting. This class can extend Symfony's AbstractMiddleware class to make it compatible with Symfony's middleware architecture.

namespace App\Middleware;

use Symfony\Component\HttpKernel\HttpKernelInterface;
use Symfony\Component\HttpKernel\Middleware\AbstractMiddleware;
use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\HttpFoundation\Response;

class RateLimitMiddleware extends AbstractMiddleware
{
    private $limit;
    private $interval;
    private $storage;

    public function __construct(int $limit, int $interval, $storage)
    {
        $this->limit = $limit;
        $this->interval = $interval;
        $this->storage = $storage;
    }

    public function handle(Request $request, $type = HttpKernelInterface::MASTER_REQUEST, $catch = true)
    {
        // Check if the user has exceeded the rate limit
        $key = 'rate_limit_' . $request->getClientIp();
        $requests = $this->storage->get($key, 0);

        if ($requests >= $this->limit) {
            return new Response('Rate limit exceeded', 429);
        }

        // Increment the number of requests for the user
        $this->storage->set($key, $requests + 1, $this->interval);

        // Continue with the request handling
        return $this->next->handle($request, $type, $catch);
    }
}

services:
    App\Middleware\RateLimitMiddleware:
        arguments:
            $limit: 100
            $interval: 60
            $storage: '@app.rate_limit_storage'

Create a rate limit storage class that will track the number of requests made by each user. This can be a simple PHP class that uses a key-value store (e.g., Redis, Memcached, or even a simple PHP array) to store the request counts.

namespace App\RateLimit;

class RateLimitStorage
{
    private $storage = [];

    public function get(string $key, int $default = 0)
    {
        return $this->storage[$key] ?? $default;
    }

    public function set(string $key, int $value, int $ttl)
    {
        $this->storage[$key] = $value;
        // You can implement expiration logic here if needed
    }
}

Configure the rate limit storage service in your services.yaml file.

services:
    app.rate_limit_storage:
        class: App\RateLimit\RateLimitStorage

Add the rate limit middleware to your Symfony application's middleware stack. You can do this in your kernel.php file.

use App\Middleware\RateLimitMiddleware;
use Symfony\Component\HttpKernel\Kernel;

class AppKernel extends Kernel
{
    protected function build()
    {
        $middleware = parent::build();
        $middleware->addMiddleware(new RateLimitMiddleware());
    }
}

With these steps, you have successfully implemented rate limiting in Symfony's HTTP kernel using middleware. This will help you control the number of requests made by each user within a specified time period.