Azure Web App Scaling: Identifying App1 Scaling Points

App1 Scaling Points

Question

You have an Azure web app named App1 that is configured to run between two and five instances. There are currently three instances of App1 running.

App1 has the following autoscale rules:

Increase the instance count by one when the CPU percentage is greater or equal to 80.

Decrease the instance count by one when the CPU percentage is less than or equal to 60.

You are evaluating the following CPU percentage of utilization for App1:

-> 60%

-> 55%

-> 50%

-> 45%

You need to identify which utilizations will cause App1 to scale in.

Answers

Explanations

Click on the arrows to vote for the correct answer

A. B. C. D.

D

Azure Monitor autoscaling allows you to scale the number of running instances up or down, based on telemetry data (metrics). Scale-in occurs when the instances are decrease. For this rule the instances are decreased when the CPU usage is 60% or lower.

https://docs.microsoft.com/en-us/azure/azure-monitor/platform/autoscale-custom-metric https://docs.microsoft.com/en-us/azure/azure-monitor/platform/autoscale-common-metrics

The autoscale rules configured for App1 specify that the instance count should increase by one when the CPU percentage is greater than or equal to 80%, and decrease by one when the CPU percentage is less than or equal to 60%. Currently, App1 has three instances running.

To identify which utilizations will cause App1 to scale in, we need to determine the CPU percentages that are less than or equal to 60%. Any CPU percentages in this range will trigger the autoscale rule to decrease the instance count by one, resulting in a scale-in action.

The CPU percentages provided are:

  • 60%
  • 55%
  • 50%
  • 45%

Out of these, only 60% is equal to the threshold for scaling in, so it will not cause a scale-in action. However, all the other CPU percentages (55%, 50%, and 45%) are less than or equal to 60%, which means that they will trigger the autoscale rule to decrease the instance count by one. Therefore, the answer is D.

To summarize:

  • App1 will not scale in at 60% CPU utilization.
  • App1 will scale in at 55%, 50%, and 45% CPU utilization.
  • The autoscale rules will decrease the instance count by one when the CPU percentage is less than or equal to 60%.