AZ-400 Question 174
Select 2You are a DevOps engineer for a company that deploys a .NET 5 web application to Azure App Service. You have configured Azure App Configuration to manage your feature flags using the Feature Manager library. You want to enable dynamic feature toggling so that changes in Azure App Configuration are applied to the web application without restarting it. Which two actions should you take to achieve this?
- A
A. Configure the application to reload feature flags on a fixed timer by calling UseAzureAppConfiguration with ConfigureRefresh in the Startup class (or Program.cs).
- B
B. Add a custom key-value pair in Azure App Configuration named 'ReloadSignal' and manually poll for changes in the application.
- C
C. Enable dynamic refresh in the Feature Manager library and specify a sentinel key in Azure App Configuration to trigger a refresh event.
- D
D. Require the Azure App Service to restart whenever a feature flag is toggled in Azure App Configuration.
Show answer and explanation
Correct answers: A, C
Explanation
To implement dynamic toggling of feature flags using Azure App Configuration, you must enable refresh capabilities in your client application. In .NET, you typically do this by calling UseAzureAppConfiguration in your app's configuration pipeline and setting up ConfigureRefresh to monitor changes. Using a sentinel key is a best practice recommended by the official Azure App Configuration documentation. This approach avoids the need to restart the app to pick up feature flag changes, making updates more seamless and reducing downtime.
- A. Correct.
A. Correct. Calling UseAzureAppConfiguration in your application� Setup (e.g., in the Program.cs or Startup.cs for .NET) and then configuring refresh with ConfigureRefresh allows the app to periodically check for updates to feature flags. This helps ensure that toggles can be updated during runtime without restarting the application.
- B. Incorrect.
B. Incorrect. While you could store a custom key-value pair, manually polling inside the application is not the recommended approach for dynamic refresh. Azure App Configuration already provides built-in refresh capabilities that can be automated.
- C. Correct.
C. Correct. Enabling dynamic refresh in the Azure App Configuration Feature Manager and setting a sentinel key (a special key in Azure App Configuration used to trigger refreshes) ensures that feature flag changes are picked up in the running application almost immediately. The sentinel key notifies your application that it needs to refresh all or specific configurations.
- D. Incorrect.
D. Incorrect. You do not need to restart the Azure App Service instance to apply feature flag changes when using Azure App Configuration with dynamic refresh. One of the main benefits of feature flags is that they can be toggled at runtime without restarting services.