How to check Elastic Premium Plan Function App allocated instance counts history

Recently I’ve been asked many times about how to check metrics of Elastic Premium Plan Function App allocated instances counts history.

We have below 3 ways to check from different perspective.

1. Go to Diagnose and solve problems --> HTTP Functions Scaling --> Number of workers allocated to the Function App

     This feature currently can be used  without charging ,  however it’s only allowed to check last 24 hours history.

2. After enabling Application insight,   we can go to Application insights --> Live metrics to check how many instances are currently allocated to this function app currently.

3. If customer wanted to check metrics for a longer time than 24 hours,  we can enable scale-controller-log (currently preview) to check. 

https://docs.microsoft.com/en-us/azure/azure-functions/functions-monitoring#scale-controller-logs

Here is the steps how we enable it.  

https://docs.microsoft.com/en-us/azure/azure-functions/configure-monitoring?tabs=v2#configure-scale-controller-logs

After enabling scale-controller-log, we can use below queries to check the instance counts history

traces

| extend CustomDimensions = todynamic(tostring(customDimensions))

| where CustomDimensions.Category == "ScaleControllerLogs"

| where message == "Instance count changed"

| extend Reason = CustomDimensions.Reason

| extend PreviousInstanceCount = CustomDimensions.PreviousInstanceCount

| extend NewInstanceCount = CustomDimensions.CurrentInstanceCount

https://docs.microsoft.com/en-us/azure/azure-functions/analyze-telemetry-data#query-scale-controller-logs

We may get the result like below which clearly records all the instance counts history.

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