RoutePreloader::onRequest

public RoutePreloader::onRequest(KernelEvent $event)

public function onRequest(KernelEvent $event) {
  // Only preload on normal HTML pages, as they will display menu links.
  if ($this->routeProvider instanceof PreloadableRouteProviderInterface && $event->getRequest()->getRequestFormat() == 'html') {

    // Ensure that the state query is cached to skip the database query, if
    // possible.
    $key = 'routing.non_admin_routes';
    if ($cache = $this->cache->get($key)) {
      $routes = $cache->data;
    }
    else {
      $routes = $this->state->get($key, []);
      $this->cache->set($key, $routes, Cache::PERMANENT, ['routes']);
    }

    if ($routes) {
      // Preload all the non-admin routes at once.
      $this->routeProvider->preLoadRoutes($routes);
    }
  }
}