gistfile1.php

**
 * Implements hook_ENTITY_TYPE_create().
 */
function custom_node_create(Drupal\Core\Entity\EntityInterface $entity) {
  if ($entity->bundle() == 'task') {
    $lock = \Drupal::lock();
    if (empty($entity->nid->getValue())) {
      // Lock tables to avoid numbers duplicate
      if (!$lock->acquire('insert_task')) {
        $lock->wait('insert_task');
      }
      // Get the last task
      $query = \Drupal::entityQuery('node')
        ->condition('status', 1)
        ->condition('type', 'task')
        ->sort('created', 'DESC')
        ->range(0, 1)->execute();
      // Autofill task number
      if (!empty($query)) {
        $last_node = Node::load(array_pop($query));
        if (empty($last_node->field_task_number->getValue())) {
          $entity->field_task_number->value = "1-" . date('m');
        } else {

          if (date('m', $last_node->created->value) == date('m')) {
            $previous_number = explode('-', $last_node->field_task_number->value)[0];
            $entity->field_task_number->value = intval($previous_number) + 1 . "-" . date('m');
          } else {
            $entity->field_task_number->value = "1-" . date('m');
          }
        }
      }
    }
  }
}

/**
 * Implements hook_ENTITY_TYPE_insert().
 */
function custom_node_insert(Drupal\Core\Entity\EntityInterface $entity) {
  if ($entity->bundle() == 'task') {
    // Release lock acquired in hook_node_create
    $lock = \Drupal::lock();
    $lock->release('insert_task');
  }
}