public function processQueueOnShutdown($newsletterID)
{
if (class_exists('MessageQueue')) {
//start processing of email sending for this newsletter ID after shutdown
MessageQueue::send("newsletter", new MethodInvocationMessage('NewsletterSendController', "process_queue_invoke", $newsletterID));
MessageQueue::consume_on_shutdown();
} else {
// Do the sending in real-time, if there is not MessageQueue to do it out-of-process.
// Caution: Will only send the first batch (see $items_to_batch_process),
// needs to be continued manually afterwards, e.g. through the "restart queue processing"
// in the admin UI.
$this->processQueue($newsletterID);
}
}