public function ReplicaDatabaseIgnoreSubscriber::checkReplicaServer in Zircon Profile 8

Same name and namespace in other branches

1. 8.0 core/lib/Drupal/Core/EventSubscriber/ReplicaDatabaseIgnoreSubscriber.php \Drupal\Core\EventSubscriber\ReplicaDatabaseIgnoreSubscriber::checkReplicaServer()

Checks and disables the replica database server if appropriate.

Parameters

\Symfony\Component\HttpKernel\Event\GetResponseEvent $event: The Event to process.

File

core/lib/Drupal/Core/EventSubscriber/ReplicaDatabaseIgnoreSubscriber.php, line 26

Contains \Drupal\Core\EventSubscriber\ReplicaDatabaseIgnoreSubscriber.

Class

ReplicaDatabaseIgnoreSubscriber

System subscriber for controller requests.

Namespace

Drupal\Core\EventSubscriber

Code

public function checkReplicaServer(GetResponseEvent $event) {

  // Ignore replica database servers for this request.
  //
  // In Drupal's distributed database structure, new data is written to the
  // master and then propagated to the replica servers.  This means there is a
  // lag between when data is written to the master and when it is available
  // on the replica. At these times, we will want to avoid using a replica server
  // temporarily. For example, if a user posts a new node then we want to
  // disable the replica server for that user temporarily to allow the replica
  // server to catch up.
  // That way, that user will see their changes immediately while for other
  // users we still get the benefits of having a replica server, just with
  // slightly stale data.  Code that wants to disable the replica server should
  // use the db_set_ignore_replica() function to set
  // $_SESSION['ignore_replica_server'] to the timestamp after which the replica
  // can be re-enabled.
  if (isset($_SESSION['ignore_replica_server'])) {
    if ($_SESSION['ignore_replica_server'] >= REQUEST_TIME) {
      Database::ignoreTarget('default', 'replica');
    }
    else {
      unset($_SESSION['ignore_replica_server']);
    }
  }
}