How do I scalably run Apex after a small delay so that all related objects exist?

Question

I'm trying to run Apex code that runs a little while after custom objects are created. The problem is that I have a few systems inserting and updating data when a customer places an order in an ecommerce system.

What I want to do in theory, is run code when an Order__c is created. In practice, there are related objects to the order such as many OrderItem__c or other objects that are created seconds later. Therefore, I can't run my logic during Order__c Insert.

I tried to use @future to add a slight delay, but sometimes it happens too fast so it's not reliable.

It seems like I could use Apex Scheduler to schedule running code 1 minute later for example. However, the documentation recommends against using this in a trigger since you can only schedule 100 things at once and this would break if hundreds of orders were placed at once.

Answer 1

A couple of options:

• You could run a scheduled job every X minutes/hours or at particular times in the day to process batch Orders (if the processing is not time crucial). Inside your batch you'd query orders created in the last X minutes/hours and process them. If you do this, allow a minute or two gap, in case a new order comes in when the batch runs and it doesn't have all related data yet.
• You could change the code in your external systems to update the order with a checkbox "Order Received" once all related data comes in. That way you can even have a trigger that runs immediately as soon as the order and its related data is in.

Answer 2

There has a way to let Apex sleep for seconds,but you have to pay attention to "Apex Governor Limits".

Long startTime = DateTime.now().getTime();
Long finishTime = DateTime.now().getTime();
while ((finishTime - startTime) < 9000) {
    //sleep for 9s
    finishTime = DateTime.now().getTime();
}

Reference the following link:
A way to make Thread Sleep in Apex