User configurable notification frequency in LAMP Web App

Question

I am developing a Web Application for businesses to track the status of their repairs & part orders that is running on LAMP (Linux Apache MySQL PHP). I just need some input as to how I should go about allowing users to customize the frequency of email notifications.

Currently, I just have a cron job running every Monday at 6:00AM that runs a php script that sends an email to each user of their un-processed jobs. But I would like to give users the flexibility of not only choosing the time they are sent at, but the days of the week as well.

One idea I had was, some way or another, storing their email notification preferences in a MySQL database, and then writing a php script to notify via email but only if the current date/time fits within the criteria they have set & write in code to prevent it from being sent twice within the same cycle. Then I could just run the cron job every minute or 5 or whatever.

Or would it be better to somehow create individual cron jobs for each user programatically via php?

Any input would be greatly appreciated! :)

Answer 1

No you are right.

Individual crons will consume many resources. Imagine 10k of users with a request to send mail at different times ... this imply 10k of tasks.

The best solution is to create a cron task that will run on your users and take the correct actions.

Iterate on your users, check the date/time set up, detect change and send mail with adding a flag somewhere so said "it's done" (an attribute last_cron_scandate or next_calculated_cron_scandate could be a good solution)