Queuing Private Messages in Drupal 8

My current project at Microserve is a Drupal 8 website that uses the Private Message module for users to send messages to each other.

In some cases though, the threads could contain hundreds of recipients so I decided that it would be good to queue the message requests so that they can be processed as part of a background process for better performance. The Private Message module does not include this, so I've written and released a separate Private Message Queue module.

Queuing a Message

The module provides a PrivateMessageQueuer service (private_message_queue.queuer) which queues the items via the queue() method.

The method accepts an array of User objects as the message recipients, the message body text and another user as the message owner. (I'm currently considering whether to make the owner optional, and default to the current user if one is not specified)

Here is an example:

$recipients = $this->getRecipients(); // An array of User objects.
$message = 'Some message text';
$owner = \Drupal::currentUser();

$queuer = \Drupal::service('private_message_queue.queuer');
$queuer->queue($recipients, $message, $owner);

These three pieces of data are then saved as part of the queued item. You can see these by checking the "queue" table in the database or by running drush queue-list.

$ drush queue-list
Queue Items Class
private_message_queue 19 Drupal\Core\Queue\DatabaseQueue

Processing the Queue

The module also provides a PrivateMessageQueue queue worker, which processes the queued items. For each item, it creates a new private message setting the owner and the message body.

It uses the PrivateMessageThread class from the Private Message module to find for an existing thread for the specified recipients, or creates a new thread if one isn't found. The new message is then added to the thread.

The queue is processed on each cron run, so I recommend adding a module like Ultimate Cron so that you can process the queued items frequently (e.g. every 15 minutes) and run the heavier tasks like checking for updates etc less frequently (e.g. once a day).

You can also process the queue manually with Drush using the drush queue-run <queue-name> command - e.g. drush queue-run private_message_queue.

$ drush queue-run private_message_queue
Processed 19 items from the private_message_queue queue in 3.34 sec.