A helper module for throttling tasks in Drupal

It is pretty common that a site needs to do something regularly, but not too often. Most frequently it is maintenance tasks done through hook_cron, like core's update_cron which limits how often it checks for new versions of a site's modules. The pattern is pretty simple - store a timestamp in the site's state when the task is executed, then before executing the task again check that the desired period has elapsed.

A colleague took another approach that I thought was interesting and worth polishing into a contrib module, so I created Periodic. Instead of each task needing to duplicate the code for storing and checking a timestamp, Periodic's cron task emits events for common periods of time which other modules can respond to as needed:

MyModuleEventSubscriber {

  public static function getSubscribedEvents() {
    $events = [];
    $events[PeriodicEvents::HOUR] = ['hourlyTask'];
    $events[PeriodicEvents::DAY] = ['dailyTask'];
    return $events;
  }

  public function hourlyTask() {
    // Do hourly task.
  }

  public function dailyTask() {
    // Do daily task.
  }

}

If a different interval is needed for a task, Periodic offers a service to check if execution should proceed:

function mymodule_cron() {
  $periodicManager = \Drupal::service('periodic.manager');

  // Limit task to every six hours.
  if ($periodicManager->execute('mymodule.crontask', 21600)) {
    // Do custom task.
  }
}