Queue notifications delay in Laravel - laravel

Question

I tried delaying each notification (or job) using Laravel queues. Still, instead of the notifications being delayed one after the other, the delay is applied to all the notifications at once. However, the delay is only applied to the first notification, and the rest are sent out simultaneously as the first message. Please, can anyone in this community help me?
This is part of the method that gets only the applicants whose admissions are accepted or rejected and then notify them individually. Unfortunately, the mail server we are using only allows sending a maximum of 30 emails per 1 minute; therefore, I need to use queuing to limit sending only (not more than) 1 email per 2 seconds.
foreach ($applications as $application)
{
$application_id = $application->id;
$admission = Admission::where('application_id', $application_id)->first();
if (empty($admission->admission_no) & $application->status === 5) {
$this->generateAdmissionNumber($application->id, $application->course_id);
$application->update(['done' => 1]);
$admissions = Admission::where('course_id', '=', $id)->get();
foreach ($admissions as $admission) {
$admission->update(['done' => 1]);
}
}
$application->done = 1;
$application->update();
$user = $application->users;
if ($user->notify_if_decision_is_made === 1)
{
$user->notify((new DecisionNotification($user))
->delay(Carbon::now()->addSeconds(2)));
}
}
I followed the guides but still have no solution. I looked at many solutions here but did not see any issues like this one.
I set QUEUE_CONNECTION=database in my .env file, added shouldQueue in the DecisionNotification file, and run php artisan queue:work from the terminal to execute the jobs. I appreciate any help.

Answer 1

The ->delay() only gives a delay to the running job. As your loop is running almost instantly, it won't delay put a delay of 2 seconds between each job.
One way to achieve what you want is:
foreach ($applications as $i => $application) {
// your code chunk
$user->notify((new DecisionNotification($user))->delay($i * 2)));
}
This results in delays as:
Job 1: 0s
Job 2: 2s
Job 3: 4s
Job 4: 6s
Job 5: 8s
...
By the way, ->delay() also accepts integer as second.

Answer 2

You can use sleep() function, which holds the loop for defined period, for example if you want to hold loop for 2 seconds, use sleep(2).
Your code should be:
foreach ($applications as $application) {
$application_id = $application->id;
$admission = Admission::where('application_id', $application_id)->first();
if (empty($admission->admission_no) & $application->status === 5) {
$this->generateAdmissionNumber($application->id, $application->course_id);
$application->update(['done' => 1]);
$admissions = Admission::where('course_id', '=', $id)->get();
foreach ($admissions as $admission) {
$admission->update(['done' => 1]);
}
}
$application->done = 1;
$application->update();
$user = $application->users;
if ($user->notify_if_decision_is_made === 1) {
$user->notify((new DecisionNotification($user))->delay(Carbon::now()->addSeconds(2)));
}
sleep(2);
}
Hope this will be useful.
Read More about sleep()