I'm developing a website (using a LAMP stack) which must handle many user-made scheduling tasks. It works as following: an user creates an event and sets a date, and others users (as many as 63) may join. A few hours before the set date, the system must email each user subscribed to that event. And that's it.
However, I have never handled scheduling, and the only tools I know (poorly) are cron and at. My plan is to create an at job for each event, which will call a script that gets all subscribers emails and mails them.
My question is: is my plan/design good? Is it scalable? Are there better options that I should be aware of?
If you would consider a proper framework that uses an application server (and not a simple webserver), Spring has a task scheduling layer that's simple to use. Scheduling jobs on the server really requires more than what a simple LAMP install can do, but I haven't used PHP in a while so maybe there's an equivalent.
Here's an article that compares some of your options.
Why a separate cron job for each event? I've done something similar thing for a newsletter with a cron job just running once per hour and if there are any newsletters to be sent it just handles them. In your case you'd have a script that runs once every hour and gets a list of users for events that happen in the desired time interval since.
It will work. As far as scalability, at the minimum make sure that the script runs in it's own process so it doesn't bog down the server unnecessarily.
Create a php-cli script perhaps?
I'm doing most of my work in Rails nowadays, and there's a wealth of background processing libraries one of them is Resque it uses the redis server to keep track of the jobs I found a PHP clone https://github.com/chrisboulton/php-resque
Might be overkill for your use case, but give it a shot perhaps
来源：https://stackoverflow.com/questions/13638323/how-to-handle-large-amounts-of-scheduled-tasks-on-a-web-server