AZ-400 Designing and Implementing Microsoft DevOps Solutions Exam

Feature Flag Implementation and Control

Feature flags allow teams to turn features on or off without deploying new code, giving dynamic control over application behavior. They are useful for gradually releasing features, rolling out feature updates, and doing A/B testing. In Azure, the App Configuration FeatureManager simplifies the implementation of feature flags.

Configuring Feature Flags

To configure feature flags in Azure App Configuration:

• Use spring.cloud.azure.appconfiguration.stores[0].feature-flags.selects[0].label-filter to apply label filters.
• Previously used properties like spring.cloud.azure.appconfiguration.stores[0].feature-flags.label are now replaced with the new label filter property.

Label filters help ensure that only specific versions of features are activated based on criteria, such as environment or version.

Integrating FeatureManager SDK

The FeatureManager SDK integrates feature flags into your applications. Implementing customizations can be done using ConfigurationClientCustomizer and SecretClientCustomizer. These customizers help in modifying client instances before connecting to App Configuration, allowing seamless integration using various credential types supported by the Azure Identity library.

Example:

import com.azure.core.credential.TokenCredential;
import com.azure.data.appconfiguration.ConfigurationClientBuilder;
import com.azure.identity.*;
import com.azure.spring.cloud.appconfiguration.config.ConfigurationClientCustomizer;

public class ConfigurationClientCustomizerImpl implements ConfigurationClientCustomizer {
    @Override
    public void customize(ConfigurationClientBuilder builder, String endpoint) {
        AzureCliCredential cliCredential = new AzureCliCredentialBuilder().build();
        ManagedIdentityCredential managedIdentityCredential = new ManagedIdentityCredentialBuilder().clientId(System.getenv("MANAGED_IDENTITY_CLIENT_ID")).build();
        ChainedTokenCredential credential = new ChainedTokenCredentialBuilder().addLast(cliCredential).addLast(managedIdentityCredential).build();
        builder.credential(credential);
    }
}

This example shows how to customize a configuration client to use various credentials, allowing flexible integration with different identity management methods.

Applying Filters and Targeting Rules

When using feature flags, you can apply filters, labels, and targeting rules for controlled, real-time toggling:

• Percentage rollouts: Gradually expose a new feature by setting a percentage of users who will receive it.
• User segmentation: Specify different groups of users who will see certain features based on set criteria.

Filters and targeting rules give you finer control over who sees which features, making it possible to test changes with select user groups before a full rollout.

Managing Conflicts with Global Properties

Be cautious of possible conflicts with Spring Cloud Azure global properties. These settings automatically pick up credentials like environment variables. If you're using custom connection methods such as a managed identity, ensure to override them using the provided customization interfaces to avoid connectivity issues.

Implementing feature flags efficiently within Azure can transform the way you manage feature releases, providing more control and flexibility in the deployment process. This capability supports continuous deployment practices where new features are released quickly and safely.

Conclusion

In this section, we learned about implementing feature flags using Azure's App Configuration FeatureManager. We covered how to configure feature flags, integrate them with applications using the FeatureManager SDK, apply filters and targeting rules, and manage potential conflicts with global properties. These techniques enable better control over feature deployment, contributing to more effective and safer continuous integration and continuous delivery (CI/CD) processes.