AZURE API MANAGEMENT LOGGER

Hello all. I have a working flow of streaming some metrics of my management instincts to power bi. (Logger piped to Event Hub piped to Stream Analytics piped to Power BI). I am using some of the context variables https://docs.microsoft.com/en-us/azure/api-management/api-management-policy-expressions#ContextVariables

But I do not see any variable that allows me to log bandwidth used. Was wondering if anybody else found a way to get the metric bandwidth per subscription key to power bi

Thanks all

Josh