I am trying to create an alert in Azure for when the percentage of server errors exceeds a given threshold. I have the total number of requests and the number of Http5xx errors, however I can not find anyway to combine these metrics to derive a "failure rate" metric. I am essentially looking for the same functionality as DataDog Formulas.
I did look though the Azure Monitor Metrics overview, however I can't find anything similar to this.
Does Azure support creating derived metrics like this? If so, where can I find some documentation or examples on how to do this?