Host multiple Apps with one Application Gateway for Containers on AKS - Part 3

Part 3 of our series shifts from infrastructure setup to practical application hosting. In this content, we demonstrate a core capability of modern traffic management: using a single Azure Application Gateway for Containers (AGFC) to expose and route traffic to multiple, independent applications residing within your AKS cluster.

This walkthrough builds directly upon the foundation established in Part 2, focusing on the configuration of Kubernetes Gateway API resources to achieve intelligent routing.

1. The Gateway API in Action: Architecture Overview

The key to hosting multiple applications is the HTTPRoute resource.

• Gateway Resource (In infrastructure namespace): The central entry point, provisioned by the AGFC, which listens for all incoming traffic.
• Applications (In dedicated namespaces): Two test applications (Nginx and Traefik Whoami) are deployed into their own namespaces with a standard ClusterIP Service, meaning they are not directly exposed to the internet.
• HTTPRoute Resources (In application namespaces): This resource links the application service to the central Gateway. Crucially, it allows you to define rules based on hostnames or paths, telling the Gateway exactly where to forward the request.

This setup ensures that the applications are isolated within their own namespaces while being securely and selectively exposed via the single, centralized Gateway.

2. Step-by-Step Multi-App Configuration

The content provides a detailed guide on deploying and configuring the applications:

• Application Deployment: Two simple applications (Nginx and Traefik) are deployed using standard Kubernetes Deployment and ClusterIP Service resources in their own namespaces (nginx-ns and traffic-ns).
• Initial Path-Based Routing: An HTTPRoute is first configured to route traffic based on a URI path prefix (e.g., /nginx or /traefik), demonstrating how the Gateway can differentiate between requests destined for different backends.
  • Example: A request to [FQDN]/traefik is successfully routed to the Traefik service.
• Advanced Hostname Routing: The configuration is then updated to use hostname-based routing. The HTTPRoute for each application is configured to match a custom URL (e.g., nginx.programmingwithwolfgang.com), allowing your applications to be accessed via clean, dedicated hostnames.

3. Key Takeaway: Separation of Concerns

By using the Gateway API’s resource model, you achieve a clean separation of concerns:

Component	Responsibility	Resource	Location
Connectivity	Public exposure & single entry point	Gateway	Infrastructure Namespace
Routing Logic	Hostname/Path matching & Backend selection	HTTPRoute	Application Namespace
Application	Core logic & port listening	Deployment / Service	Application Namespace

This pattern allows application developers to manage their routing rules (HTTPRoute) without needing permissions to modify the central infrastructure (Gateway).

4. Conclusion

Part 3 validates the flexible and powerful traffic management capabilities provided by the Kubernetes Gateway API when combined with the Azure Application Gateway for Containers. By successfully routing different hostnames to separate backends using the HTTPRoute resource, we demonstrate how a single, powerful external gateway can efficiently serve a multi-application environment. This pattern is essential for modern, scalable AKS deployments where application teams need autonomy over their exposure while benefiting from centralized, high-performance infrastructure.

What’s Next?

With the ability to route traffic to multiple applications established, the foundation is now set for implementing advanced networking features, including:

• Configuring Azure DNS to point your custom domain to the Gateway’s public hostname.
• Implementing automated TLS certificates (HTTPS) using Cert-Manager for secure connections.

You can find all the code sample on GitHub.

This post was AI-generated based on the transcript of the video “Host multiple Apps with one Application Gateway for Containers on AKS - Part 3” and reviewed by me.

Video - Host multiple Apps with one Application Gateway for Containers on AKS - Part 3