Implement feature flags by using Azure App Configuration Feature Manager

In this guide, we explain how to implement feature flags using the Azure App Configuration Feature Manager. Feature flags act as switches within your code, allowing you to enable or disable features without redeploying your application.

Imagine rolling out a new feature with the ability to deploy its code in an "off" state. When you're ready to enable the feature, simply flip the switch. This approach not only streamlines deployments but also provides robust control over your software releases.

Feature flags bring significant benefits:

• They allow for safer testing in production environments by enabling features for a limited group.
• They facilitate A/B testing without full rollouts.
• They offer immediate rollback capabilities if a feature causes issues.

Azure App Configuration Overview

Azure App Configuration is a centralized service for managing application settings and feature flags. Instead of hard-coding configuration values, you manage them dynamically through this service, which is essential for modern, cloud-based applications.

One of its key strengths is seamless integration with the Azure ecosystem. This makes it a natural fit for DevOps practices by ensuring that application configurations remain synchronized with your deployment pipelines.

Feature Management

Feature management decouples feature releases from code deployments. This means you can quickly toggle feature availability without a full rollback. At its core, this approach uses feature flags (or toggles), allowing you to adjust a feature’s lifecycle dynamically—whether through gradual rollouts or through targeted user groups.

The Feature Management Library, part of the Azure SDK, abstracts the complexity of communicating with Azure App Configuration. This allows you to focus on building your application logic with a simplified interface for feature flag management.

The library makes it easy to retrieve and manage feature flags, easing the integration of dynamic behavior into your .NET applications.

Setting Up Azure App Configuration

Setting up Azure App Configuration for feature flags is a straightforward process. Follow these steps to configure your store:

1. Log into the Azure Portal: Access your Azure account.
2. Create a New App Configuration Store: Navigate to "Create a Resource" and select App Configuration from the Azure Marketplace. Click "Create" to begin configuring your store.

When configuring the store, you will need to set parameters such as:

• Subscription and Resource Group: Select the appropriate options for your project.
• Name and Region: Provide a unique name and choose a region that is closest to your users.
• Pricing Tier: Consider starting with the free tier for testing purposes.

Once your store is set up, define your feature flags by navigating to the Feature Management section and clicking the "Add" button. Enter a key (used in your code), add an optional description, and configure the conditions under which the flag should enable.

Security is paramount. Configure Access Control (IAM) for your App Configuration store by assigning appropriate roles—such as Contributor or Reader—to users or groups.

After setting up and securing your configuration, validate it either programmatically or through the Azure Portal.

Using Feature Flags in Your Code

The Feature Manager Library simplifies integrating feature flags into your code. Follow these steps:

1. Add Necessary NuGet Packages: Include both Azure App Configuration and Feature Management in your project.
2. Configure Your Application: In your Startup.cs file, add Azure App Configuration and Feature Management to your services.

// 1 - Setup Configuration in Startup.cs
public void ConfigureServices(IServiceCollection services)
{
    services.AddAzureAppConfiguration();
    services.AddFeatureManagement();
}

3. Create a Feature Service: Build a service that encapsulates feature flag checks. Use the IFeatureManager to determine if a feature is enabled.

// 2 - Checking Feature Flag Status
using Microsoft.FeatureManagement;

public class FeatureService
{
    private readonly IFeatureManager _featureManager;

    public FeatureService(IFeatureManager featureManager)
    {
        _featureManager = featureManager;
    }

    public async Task<bool> IsFeatureEnabledAsync(string featureName)
    {
        return await _featureManager.IsEnabledAsync(featureName);
    }
}

4. Integrate Feature Flags Within Controllers: Inject the FeatureService into your controllers to determine which view or action to execute based on the feature flag's state.

// 3 - Using Feature Flags in a Controller
public async Task<IActionResult> Index()
{
    if (await _featureService.IsFeatureEnabledAsync("BetaFeature"))
    {
        // Code to execute if the feature flag is enabled
        return View("BetaFeatureView");
    }
    else
    {
        // Code to execute if the feature flag is disabled
        return View("StandardView");
    }
}

Conclusion

Feature flags are an essential tool in modern software development, particularly within DevOps workflows. By using Azure App Configuration, you centralize control over your application's behavior, enabling dynamic feature management without the need for constant redeployments.

This article provided an in-depth overview of feature flag concepts, a step-by-step guide on setting up Azure App Configuration, and practical examples for integrating feature flags into your code. Embracing this approach can enhance your application’s flexibility and responsiveness to change.

For further reading on Azure and DevOps best practices, explore the Azure Documentation and DevOps practices.

Happy coding!