Deploying C# .NET Applications to Azure Kubernetes Service (AKS)

This module will guide you through the process of deploying your C# .NET applications to Azure Kubernetes Service (AKS), a managed Kubernetes service that simplifies deploying, managing, and scaling containerized applications. We'll cover the essential steps from containerization to deployment and basic management.

Understanding Kubernetes Concepts

Before deploying, it's crucial to grasp fundamental Kubernetes concepts. These building blocks are essential for orchestrating your containerized applications.

Pods are the smallest deployable units in Kubernetes.

A Pod represents a single instance of a running process in your cluster. It can contain one or more containers that share resources like network and storage.

Pods are the fundamental building blocks of Kubernetes. They encapsulate an application container (or multiple tightly coupled containers), storage resources, a unique network IP, and options that govern how the container(s) should run. While you can run multiple containers in a single Pod, it's generally recommended to keep Pods focused on a single primary container for simplicity and maintainability.

Deployments manage stateless application updates and scaling.

Deployments provide declarative updates for Pods and ReplicaSets. They describe the desired state of your application, allowing Kubernetes to manage updates and rollbacks.

Deployments are a Kubernetes object that manages a set of identical Pods. They enable you to describe your application's desired state, and the Kubernetes control plane will work to bring the actual state to match the desired state. Deployments are ideal for stateless applications, allowing for rolling updates, rollbacks, and scaling without downtime.

Services expose your applications to the network.

Services provide a stable network endpoint for a set of Pods, abstracting away the dynamic nature of Pod IPs. This allows other applications or external users to reliably access your deployed services.

A Kubernetes Service is an abstraction that defines a logical set of Pods and a policy by which to access them. Services are crucial for enabling communication between different parts of your application, or between your application and the outside world. They provide a consistent IP address and DNS name, even as Pods are created, destroyed, or rescheduled.

Containerizing Your .NET Application

To deploy to AKS, your .NET application needs to be containerized using Docker. This involves creating a Dockerfile that specifies how to build your container image.

A typical Dockerfile for a .NET Core application uses a multi-stage build. The first stage uses a .NET SDK image to build and publish your application. The second stage uses a lightweight runtime image (like mcr.microsoft.com/dotnet/aspnet:8.0-alpine) to create a smaller, more efficient final image containing only the published application and its runtime dependencies. This process ensures your application is packaged with everything it needs to run in a containerized environment.

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Key steps in the Dockerfile include:

Base Image: Selecting an appropriate .NET runtime image.
Working Directory: Setting the directory where your application code will reside.
Copying Files: Copying your application's source code or published output into the image.
Building/Publishing: Executing the .NET build or publish command.
Exposing Ports: Specifying the port your application listens on (e.g., 80 for HTTP).
Entrypoint/CMD: Defining the command to run when the container starts.

What is the primary benefit of using a multi-stage Docker build for .NET applications?

It results in a smaller, more efficient final image by separating the build environment from the runtime environment.

Building and Pushing the Docker Image

Once your Dockerfile is ready, you'll build the Docker image and push it to a container registry. Azure Container Registry (ACR) is a common choice for AKS.

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The commands typically involve:

code
```
docker build -t .azurecr.io/: .
```
to build the image.
code
```
docker push .azurecr.io/:
```
to push it to ACR.

Creating and Configuring Azure Kubernetes Service (AKS)

You'll need an AKS cluster to deploy your application. This can be provisioned through the Azure portal, Azure CLI, or ARM templates.

Ensure your AKS cluster is configured to pull images from your Azure Container Registry. This is typically done by creating an ACR integration or by configuring image pull secrets.

Defining Kubernetes Manifests (YAML)

Kubernetes resources are defined using YAML manifest files. You'll typically need at least a Deployment and a Service manifest.

A Deployment manifest specifies:

The container image to use (from ACR).
The number of replicas (Pods) to run.
Update strategies (e.g., rolling updates).
Resource requests and limits for the Pods.

A Service manifest specifies:

The type of service (e.g.,
code
```
LoadBalancer
```
for external access).
The port your application listens on.
Selectors to match the Pods managed by the Deployment.

What is the purpose of a Kubernetes Service manifest?

To provide a stable network endpoint and access policy for a set of Pods.

Deploying to AKS

With your manifests ready and your cluster configured, you can deploy your application using

code

kubectl

Key

code

kubectl

commands:

code
```
kubectl apply -f deployment.yaml
```
: Applies the Deployment manifest.
code
```
kubectl apply -f service.yaml
```
: Applies the Service manifest.
code
```
kubectl get pods
```
: Checks the status of your Pods.
code
```
kubectl get services
```
: Checks the status of your Services and their external IPs.

Monitoring and Management

Once deployed, you can monitor your application's health, scale it, and perform updates. AKS provides integration with Azure Monitor for comprehensive logging and metrics.

Regularly check your Pod logs (kubectl logs <pod-name>) and events (kubectl get events) to diagnose any issues.

Learning Resources

Azure Kubernetes Service (AKS) Documentation(documentation)

The official Microsoft documentation for Azure Kubernetes Service, covering all aspects from creation to management.

Deploy a .NET application to Azure Kubernetes Service(tutorial)

A step-by-step tutorial specifically for deploying .NET applications to AKS, including Dockerization and Kubernetes manifests.

Kubernetes Documentation - Deployments(documentation)

Official Kubernetes documentation explaining the concepts and usage of Deployments for managing stateless applications.

Kubernetes Documentation - Services(documentation)

Official Kubernetes documentation detailing how Services provide network access to Pods and abstract away network complexities.

Dockerfile best practices(documentation)

Best practices for writing efficient and maintainable Dockerfiles, including multi-stage builds.

Azure Container Registry Documentation(documentation)

Documentation for Azure Container Registry, a managed Docker registry service for storing and managing private container images.

Kubectl Cheat Sheet(documentation)

A handy reference for common kubectl commands used to interact with Kubernetes clusters.

Introduction to Azure Kubernetes Service (AKS) - Video(video)

A foundational video explaining what AKS is and its benefits for deploying containerized applications.

Building and Deploying Microservices with .NET and Kubernetes(video)

A practical video demonstrating the end-to-end process of building and deploying .NET microservices to Kubernetes.

Kubernetes YAML Explained(video)

A clear explanation of Kubernetes YAML manifests, covering the structure and purpose of common resource definitions.

Deploying to Azure Kubernetes Service