We would like to notify the customer that the resource usage on his subscription has reached a certain level (e.g. 80% of a limit). How to configure such notifications?
You can configure limit notifications, follow the instructions from the documentation. No additional changes with the event handlers are required.
If the notification is to be sent out will be checked with each daily billing process - if the conditions configured (Send Frequency, Limit Pct) will be satisfied, the customer will receive the notification. The resource rate in the service plan must be configured to collect resource usage. If there are resources which are included to the plan as plain and a part of composite resource, then total purchased amount is taken into account when sending limit notifications: (Included+Additional) in singular resource rate plus (Included+Additional) in all composite rates where the resource is included as a subresource.