I am having a project in Laravel. In database I have a status column, which shows if exam is started or not. I had an idea in the waiting room checking every single second if the status was changed or not, if changed to 1, when the exam starts, but I am so new to Laravel and everything else, that I even don't get the main idea how I could do this, I don't ask for any code, just for the lead, to move on. yeah, hope someones gets me. Thanks if someone answers me.
4 Answers
Check about laravel cron jobs. You will need a class implementing ShouldQueue interface and using Dispatchable, InteractsWithQueue, Queueable, SerializesModels; With regards to the storage of the jobs i do recommend Redis or SQS. In order to keep monitoring the queue in production think about installing supervisor. Further information here: Queues
Your plan can work, it is called polling.
Basically, you will want to call
setInterval(function() {
//your code here
}, 1000);
setInterval is a function that receives two parameter. The first is a callback function, that will periodically be executed and the second is the length of the period in milliseconds (1000 milliseconds is a second).
Now, you will need to implement your callback function (Javascript, of course) to send an AJAX request to a Laravel action. You will need to look into XMLHttpRequest and its usages, or you can use some libraries to simplify your task, like jQuery or Axios.
On Laravel's side you will need to implement an action and a Route for it. (read this: https://appdividend.com/2022/01/22/laravel-ajax/)
Your Laravel will need to load data from your database, you can use Eloquent for this purpose or raw queries and then respond the POST request with the result.
Now, in your Javascript at the AJAX request's code you will need to have a callback function (yes, a callback inside a callback) which will handle the response and the the changes.
I know you specified "when the column on db changes..." but if it's not a strict-requirement you might want to consider implementing event-based architecture. Laravel has support for model events, which essentially allows you to run certain assertions and controls when a model created, updated, deleted etc.
class Exam extends Model
protected static function booted()
{
static::updated(function ($exam) {
if($exam->status=='your-desired-status'){
//your actions
}
//you can even in cooperate change controls
if ($exam->isDirty('status')){
//means status column changed
});
}
}
Of course this solution applies only if Database in question is in Laravel's reach. If database data changes outside the Laravel application these event listeners won't help at all.
What about leveraging Observers? Also instead of having a status boolean, you could take a similar approach that Laravel has done for soft deletes and set exam_started_at. This way you can also keep track of time stamp and state all in one column. Also, observers are immediate rather than pushing them into a queue. Then generate a websocket event that can report back to your front end, if needed.
check out Laravel observer and soft delete documentation.
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