LimitCacheTags.php

<?php

namespace Drupal\your_module\StackMiddleware;

use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\HttpKernel\HttpKernelInterface;

/**
 * Reduces the number of cache tags in the response.
 */
class CacheTagsControlMiddleware implements HttpKernelInterface {

  /**
   * The wrapped HTTP kernel.
   *
   * @var \Symfony\Component\HttpKernel\HttpKernelInterface
   */
  protected $httpKernel;

  /**
   * Constructs a new CacheTagsControlMiddleware object.
   *
   * @param \Symfony\Component\HttpKernel\HttpKernelInterface $http_kernel
   *   The HTTP kernel.
   */
  public function __construct(HttpKernelInterface $http_kernel) {
    $this->httpKernel = $http_kernel;
  }

  /**
   * {@inheritdoc}
   */
  public function handle(Request $request, $type = self::MASTER_REQUEST, $catch = TRUE) {
    $response = $this->httpKernel->handle($request, $type, $catch);

    // This could be replaced by config and cached...which I think config is cached by default.
    // Or some other way of filtering requests can be used.
    $path = $request->getPathInfo();
    $paths_to_control = [
      '/a/path',
    ];
    
    $max_tags = 625;

    if (in_array($path, $paths_to_control)) {
      $edge_cache_tags = $response->headers->get('edge-cache-tag');
      if ($edge_cache_tags) {
        $tags_array = explode(',', $edge_cache_tags);
        if (count($tags_array) > $max_tags) {
          $tags_array = array_slice($tags_array, 0, $max_tags);
          $response->headers->set('edge-cache-tag', implode(',', $tags_array));
        }
      }

      $purge_cache_tags = $response->headers->get('x-acquia-purge-tags');
      if ($purge_cache_tags) {
        $tags_array = explode(' ', $purge_cache_tags);
        if (count($tags_array) > $max_tags) {
          $tags_array = array_slice($tags_array, 0, $max_tags);
          $response->headers->set('x-acquia-purge-tags', implode(' ', $tags_array));
        }
      }
    }
    return $response;
  }

}