Queue emails to send in background

@gilbertdelyon
You created a lot of threads and issues on Drupal.org regarding this topic. Several module maintainers helped you.

Unfortunately, you did not share your solution and the code of your custom module which could help others. This is a bit sad.

Maybe you can rethink this and share your code?

Thanks in advance.

@gilbertdelyon,

It is good to know that you are able to achieve it with custom module. Request you to help us by sharing it.

Regards
Ajaykumar Gudivada

Sorry, I am only a poor old (very old!) part time hobyist self made developper and I did not have in mind that my poor skills could help confirmed coders!
In addition I have been very busy these monthes without any time for Drupal.
So, let me explain how it works in my very humble module:
Please notice that this custom module is taylor made for my needs, so you will see hereunder only some abstracts in regard with mailing:

1 - Queueing:
Drupal queing is very simple to use (you only have to google a bit!):
Somewhere in your code you will prepare the data that will be used for your mailng and then, thanks to the above function you will queue this data. Then it will be used at next CRON .

/**
  * Somewhere in you module
  * for example in a custom service
  *
  */
 
  /**
   * Queueing function
   * $notifdata is an array that will include all the resqted stuff for mail processing (subject, content, to, from,...)
   * Each item of the array is for ONE email
   *
   */  
  protected function queueing($notifdata){ 
  
        $queue = \Drupal::queue('my_queue_name');
        $queue->createQueue();             

	foreach ($notifdata as $item => $value){
		$queue->createItem($value); //One queue item per email
	}//end foreach
        
    }//end function

Cannot be more simple!

2 - Unqueueing:
Unqueing can be made in different ways:
- Old fashion by way of a hook_cron() function
- New fashion by way of a queueWorker.
As I am an old guy I will use the old fashion.

So, here is the hook_cron() function in my_module.module file

/**
 * Implements hook_cron()
 * This function will send email at each crom
 * 
 */

function mycustommodule_cron() {

     //My queue
      $myqueue = \Drupal::queue('my_queue_name');
      
      // Number of queue items to be sent at each cron 
      // (You have to set this value somewhere in you module config)
      $nbitems = mycustommodule_settings()["maxiItemsPerCron"];
      
      //Items processing
      for ($i=0; $i<($nbitems); $i++){
       
        // Test if items  to be processed from the queue
        // $queue->claimItem() returns only one item from the queue
        if ($queue_item =  $myqueue->claimItem()) {
                
            //Extract data from item
            $notifdata = $queue_item->data;
            
            //Send Email (using a custom service )
            $notif = \Drupal::service('my_custom_service');
            $sendnotif = $notif->sendnotif2users($notifdata); // sendnotif2users() method is now trigered
            //Delete item if success
            if($sendnotif){
                 $myqueue->deleteItem($queue_item);
            }//fin if

        }//fin if
      
    }//fin for
}//end function

3 - Sending the emails
In my custom module, heach time an item will be unqueued in hook_cron() the sendnotif2users() method (from my_custom_service) will be triggered.
You can also simply use a function. IMHO services is the best way.

/**
 * In my_custom_service file
 *
 */
namespace Drupal\node2notifs\NotifServices;

use Drupal\Core;

//Compléments pour envoi mails avec SymfonyMailer
use Symfony\Component\Mailer\Transport;
use Symfony\Component\Mailer\Mailer;
use Symfony\Component\Mime\Email;

/**
 * This function will mainly process the email content  and trigger the sending process (one email per target adress)
 *
 */ 
 
 public function sendnotif2users($notifdata) { 
                
	// Prossessing the email content
	$this->mailcontents($notifdata); // mailcontents() to be coded as as per your needs
                
        // Targets
	$targets = ["name1@domain1","name2@domain2","name3@domain3","name4@domain4", ];// array of all target email adresses
               
        //Sending loop
        foreach($targets as $item => $to){

              $this->to = $to;
              $this->sendEmail();//here we send an email only ONE email 
				   
        }//fin foreach
                
         return TRUE;  //This will allow queue item delete in  hook_cron()
               
 }//fin public  function

4 - And finally the mail is sent via SymfonyMailer
Of course you have to install Symfony Mailer and use the relative classes in your service (see heareabove)

 /**
 * This function will send the email with help of SymfonyMailer
 *
 */
 
 public function sendEmail() {

        $email = (new Email())
            ->from( \Drupal::config('system.site')->get('mail'))
            ->to($this->to)
            //->cc('cc@example.com')
            //->bcc('bcc@example.com')
            //->replyTo('replyto@example.com')
            //->priority(Email::PRIORITY_HIGH)
            ->subject($this->subject)
            ->text( $this->plaintextbodybuilder() )
            ->html( $this->htmlbodybuilder() );

        $transport = Transport::fromDsn('sendmail://default');
        $mailer = new Mailer($transport);
        $mailer->send($email);

    }//fin function

Please forgive some possible mistakes, I am only a poor hobbyist.
I hope this can help

Thank you so much! @gilbertdelyon for sharing these details.

Symfony Mailer has inbuilt support for Messenger with precisely this feature: https://symfony.com/doc/current/mailer.html#sending-messages-async

I'm presently working on Symfony Messenger integration, which is effectively Emails to Queues suggested by this issue.

See ✨ Add Symfony Messenger support for async messsages (emails as queues) Active

As of this writing, Messenger integration is in active development; not ready for public consumption yet. Though it works great locally!

Great thanks @dpi. We now have two issues for the same thing, so let's close one as a duplicate.

Despite this issue being older I'm going to close as a dupe as suggested.

I think the solution is different enough to support this.

I think there could ultimately be multiple solutions implemented. If a different proposal and solution is devised then this issue could be reopened.

#13 ✨ Queue emails to send in background Closed: duplicate
Sounds good. I am impatiently waiting for the next release!

The messenger code is now public. Have at it.