Event Response not firing anonymous user

Question

I have a module in drupal8 which only job is on an event response is to redirect a URL. It works fine for everyone except anonymous users. How do I give the module privileges to fire on every user no matter if the are logged in or not.

This is the geographic_me_redirect.services.yml

services:
  me_redirect.process_me_request:
    class: Drupal\me_redirect\EventSubscriber\ResponseSubscriber
    arguments: []
    tags:
      - { name: event_subscriber }

This is the response

class ResponseSubscriber implements EventSubscriberInterface
{


    /**
     * Constructor.
     */
    public function __construct()
    {

    }

    /**
     * {@inheritdoc}
     */
    public static function getSubscribedEvents()
    {

        ///$events[KernelEvents::REQUEST][] = ['onRouteMatch', 27];
        //-- fires the event in the kernal early oo page load 20
        $events[KernelEvents::RESPONSE] = ['process_language_request',0];
        //-- For redirecting to another domain

        return $events;
    }



    public function process_language_request(FilterResponseEvent $event)
    {

    return my logic

    }
}

Answer 1

You can't do this when the redirect is already stored in the internal page cache. Because anonymous traffic is served from this cache before any event is fired.

You have to use this kill switch:

\Drupal::service('page_cache_kill_switch')->trigger();

If you put this in your event subscriber and clear the cache, then you prevent, that the response is cached in the internal page cache.

Answer 2

If you just want redirect to URL you can use class like this:

<?php

namespace Drupal\my_event\EventSubscriber;

use Drupal\Core\Cache\CacheableMetadata;
use Drupal\Core\Routing\TrustedRedirectResponse;
use Drupal\Core\Url;
use Symfony\Component\EventDispatcher\EventSubscriberInterface;
use Symfony\Component\HttpKernel\Event\GetResponseEvent;
use Symfony\Component\HttpKernel\KernelEvents;

/**
 * Class MyEventSubscriber.
 *
 * @package Drupal\my_event
 */
class MyEventSubscriber implements EventSubscriberInterface {


  /**
   * {@inheritdoc}
   */
  static function getSubscribedEvents() {
    $events[KernelEvents::REQUEST][] = ['processEvent', 0];
    return $events;
  }

  /**
   * Redirect and cache with anonymous user
   * @param \Symfony\Component\HttpKernel\Event\GetResponseEvent $event
   * @param \Drupal\Core\Url $url
   */
  protected function setResponse(GetResponseEvent $event, Url $url) {
    $response = new TrustedRedirectResponse($url->toString(), 301);
    $response->addCacheableDependency(CacheableMetadata::createFromRenderArray([])
      ->addCacheTags(['rendered']));
    $event->setResponse($response);
  }

  /**
   * Process with difference condition
   * @param \Symfony\Component\HttpKernel\Event\GetResponseEvent $event
   */
  public function processEvent(GetResponseEvent $event) {
    $logic = $this->checkLogic();
    if ($logic) {
      $this->setResponse($event, Url::fromUri("https://www.example.com"));
    }
  }

  /**
   * Check logic redirect
   * @return boolean logic
   */
  protected function checkLogic() {
    return $logic;
  }
}

Magic here is method setResponse. I use event KernelEvents::REQUEST and set cache in method setResponse. It's working with anonymous user.