a customer of mine would like to create an alert for a service based on a metric evaluated against baseline data to avoid getting alerts in the morning hours when less users are using this service.
Normally this is not a problem but the metric my customer would like to use (user sessions) is not in the set of default benchmark data. Is there a way to add this metric to baseline calculation? If not is it possible to add a static baseline for only this metric and stay on automatic calculated baselines for all other metrics?
I just started thinking if comparison against baseline is best solution for your case and I believe that there might be better ways to do it:
How about creating alert with two conditions:
User sessions < x
Unique users > y
(if you use 2018 you can add multiple metric conditions, in 17 and earlier versions, you can take advantage of Auxiliary metric and Output filters)
Another way (available in 2018 only, I'm afraid) is dimension filter defined on Hour of the day dimension. using it you can define alert which might be triggered during selected hours only.
Please, let me know if any of those ideas helps in your case