How to process single queue item using QueueWorker on cron runs?

Question

For each cron run, I would like to be able to process only 1 item in my queue using QueueWorker. At the moment it seems to me that Drupal keep processing items until it reaches the time parameter for the queue worker. I want to change this behavior to process 1 queue item at a time regardless of the time param. This is what I have so far:

/**
 * Processes Tasks.
 *
 * @QueueWorker(
 *   id = "data_provider_queue",
 *   title = @Translation("task worker: data provider queue"),
 *   cron = {"time" = 60}
 * )
 */
class SomeQueueWorker extends QueueWorkerBase {
  /**
   * {@inheritdoc}
   */
  public function processItem($data) {
       // Do something with data.
       // This seems to keep getting called for more than 
       // one item in the queue. How do we change that?
  }
}

Is this possible with QueueWorker or should I just process queue items in a cron hook manually?

Answer 1

Queue workers are meant to be processed in batches, not 1-each-cron-run.

If you want to process only a single item every cron run, then use the cron-hook.

Answer 2

As per @Eyal's answer, process it via a cron hook like:

/**
 * Implements hook_cron().
 */
function example_cron() {
  $queue = \Drupal::queue('data_provider_queue');

  if ($queue_item = $queue->claimItem()) {

    /** @var \Drupal\Core\Queue\QueueWorkerInterface $queue_worker */
    $queue_worker = \Drupal::service('plugin.manager.queue_worker')
      ->createInstance('data_provider_queue');

    try {
      // Process only 1 queue item per cron run.
      $queue_worker->processItem($queue_item->data);
      $queue->deleteItem($queue_item);
    }
    catch (\Exception $e) {
      // Something went wrong...
    }
  }
}

And do not forget to adjust your QueueWorker and discard the cron time, so that it only processes via your cron hook:

/**
 * Processes Tasks.
 *
 * @QueueWorker(
 *   id = "data_provider_queue",
 *   title = @Translation("task worker: data provider queue"),
 * )
 */