Add countSession for a user in SessionManager

Problem/Motivation

I noticed while working on a contrib module that it would be good, if it would be possible to fetch the count of open sessions for a single user.

The module creates locks for content, so only a single user can edit it. The idea here now is that when user logs out it should remove open locks. As a user can log in to multiple browser and can have multiple sessions, it needs to make sure that this is the last open session.

As a workaround in content_lock following is used:

  // Only do the database check if the original drupal session manager is used.
  // Otherwise its not sure if sessions table has correct data. As it would be
  // a common practice to extend the Class, instanceof is not used here!
  if (get_class(Drupal::service('session_manager')) == \Drupal\Core\Session\SessionManager::class) {
    $query = \Drupal::database()
      ->select('sessions');
    $query->condition('uid', $account->id());
    $query = $query->countQuery();
    $session_count = (int) $query->execute()->fetchField();
  }

See FR #2937733: Remove locks on user log out

Proposed resolution

Add new method for counting the open sessions to SessionManager

Remaining tasks

• Add new method
• Add tests

User interface changes

None

API changes

Add new countSession() method to SessionManager

Data model changes

None