Keeping Your .NET App Configuration Fresh with Azure App Configuration

Managing application settings is critical for modern applications, especially when your app needs to adapt dynamically to changes without redeployment. In this blog post, I’ll share how you can use Azure App Configuration in a .NET application to keep your configuration fresh, reliable, and responsive to change.

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When working with Azure App Configuration, you can achieve dynamic updates to your app settings by leveraging refresh techniques, automatic triggers, and manual refreshes. Here’s how I approach it, broken into manageable steps.

Setting Up Azure App Configuration in .NET

The first step to using Azure App Configuration effectively is to ensure it’s integrated into your .NET app. With Azure App Configuration, your settings are stored in a centralized location as key-value pairs, which makes it easier to manage and update them without the need for redeployment. Additionally, feature flags allow you to toggle features on and off dynamically.

To connect Azure App Configuration in your .NET app, you’ll typically use the Azure.Data.AppConfiguration NuGet package. Here’s an example of how I set it up in the program file using TypeScript syntax for clarity:

import { builder } from 'AspNetCore';
import { AzureAppConfiguration } from 'Azure.Data.AppConfiguration';

builder.Services.AddAzureAppConfiguration((options) => {
    options.Connect('Your-Connection-String')
        .Select('App:*') // Load all keys that start with 'App:'
        .ConfigureRefresh((refreshOptions) => {
            refreshOptions
                .Register('App:Settings:Key', true) // Register the key for refresh
                .SetCacheExpiration(TimeSpan.FromMinutes(5)); // Set cache expiration
        });
});

builder.Services.AddControllers();

This snippet ensures that the app connects to Azure App Configuration and sets up automatic refresh behavior for specific keys.

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Understanding Refresh Behavior

Once Azure App Configuration is integrated, the next step is to control how and when configuration values get refreshed. Without refresh configuration, your app will use the settings it loads on startup and won’t reflect updates until the app restarts.

Automatic Refresh

Automatic refresh is the most straightforward way to keep your app up-to-date with configuration changes. By registering specific keys with the ConfigureRefresh method, you can instruct your app to periodically check for updates.

Here’s how I configure automatic refresh:

options.ConfigureRefresh((refreshOptions) => {
    refreshOptions
        .Register('App:Settings:FeatureFlag', true) // Refresh when this key changes
        .SetCacheExpiration(TimeSpan.FromSeconds(30)); // Check every 30 seconds
});

In this setup, the app monitors a specific key (App:Settings:FeatureFlag) and updates the configuration if the value changes. The cache expiration ensures that the app doesn’t overwhelm the configuration store with frequent requests.

Trigger-Based Refresh

Trigger-based refresh is another efficient way to handle configuration updates. Instead of refreshing all configuration values, you can set up triggers for specific keys that act as change detectors.

For example, if you have a key that controls feature toggles, you can register it to trigger a refresh of the configuration whenever it changes:

options.ConfigureRefresh((refreshOptions) => {
    refreshOptions
        .Register('App:Settings:TriggerKey', true); // This key triggers a refresh
});

This method ensures that updates are processed only when critical keys change, reducing unnecessary requests.

Manual Refresh for On-Demand Updates

While automatic refresh is helpful, there are cases where you need to control the refresh process manually. For instance, if you’re running a long-lived service and want to fetch updates only during specific intervals or events, you can use the RefreshAsync method.

Here’s how I implement manual refresh in my applications:

import { ConfigurationRefresher } from 'Azure.Data.AppConfiguration';

const configurationRefresher = new ConfigurationRefresher();

// Trigger a manual refresh
await configurationRefresher.RefreshAsync();

This approach is particularly useful during debugging or testing when you want to ensure your app reflects the latest configuration values immediately.

Handling Feature Flags Dynamically

Feature flags are a powerful tool in Azure App Configuration. They let you enable or disable specific parts of your application dynamically. For example, you might want to roll out a new feature to a subset of users or quickly disable a feature if it’s causing issues.

To use feature flags effectively, you can configure your app to fetch and monitor them as part of the configuration setup:

options.UseFeatureFlags((featureFlagOptions) => {
    featureFlagOptions.CacheExpirationInterval = TimeSpan.FromMinutes(1); // Refresh feature flags every minute
});

With this configuration, the app will check for updates to feature flags regularly, ensuring that your app behaves according to the latest settings.

In your application code, you can then use the feature flag values to control functionality:

if (config.GetValue<boolean>('App:FeatureFlags:NewFeatureEnabled')) {
    // Enable new feature
    console.log('New feature is enabled!');
} else {
    // Fallback to default behavior
    console.log('New feature is disabled.');
}

This allows you to toggle features on and off without modifying the app’s code or redeploying.

Best Practices for Managing Refresh Intervals

Here are some strategies I’ve found helpful for managing refresh intervals effectively:

Use Reasonable Cache Expirations: Avoid extremely short intervals to prevent unnecessary load on your configuration store. A 30-second to 5-minute interval often works well.
Register Only Critical Keys: Only register keys that require frequent updates for refresh to reduce overhead.
Test Refresh Scenarios: Simulate configuration changes during testing to ensure your app responds as expected.
Leverage Diagnostic Logs: Enable logging to monitor how frequently your app fetches configuration values and identify potential issues.

Wrapping Up

Keeping your configuration fresh and reliable is a vital part of managing modern .NET applications. With Azure App Configuration, you can leverage automatic refresh, manual updates, and trigger-based refreshes to ensure your app is always in sync with the latest settings. Feature flags add another layer of flexibility, allowing you to manage functionality dynamically.

By carefully balancing refresh intervals and selecting which keys to monitor, you can build robust and adaptable applications that handle changes seamlessly. Configuration management doesn’t have to be static—Azure App Configuration makes it dynamic, flexible, and efficient.