Kubernetes

🟢 1️⃣ What is Kubernetes?

• Kubernetes (K8s) is a container orchestration platform.

• It manages, deploys, and scales containers automatically.

• Think of it as a manager for Docker containers in a large system.

Analogy:

• Docker = single shipping container

• Kubernetes = entire shipping port with cranes, storage, and delivery trucks

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🟢 2️⃣ Why Kubernetes for .NET Core?

1. Scaling: Automatically increase or decrease the number of instances.

2. Self-healing: Restarts failed containers automatically.

3. Load balancing: Distributes traffic between multiple instances.

4. Rolling updates: Update services without downtime.

5. Service discovery: Easy communication between microservices.

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🟢 3️⃣ Key Kubernetes Concepts

Term	Meaning
Pod	Smallest deployable unit (usually 1 container, can have multiple)
Node	A server (VM or physical machine) running Kubernetes
Cluster	A group of nodes managed by Kubernetes
Deployment	Defines how many replicas of a pod to run and manages updates
Service	Exposes pods internally or externally for communication
ConfigMap	Stores configuration (key-value) for pods
Secret	Stores sensitive info (passwords, API keys) securely
Namespace	Logical separation of resources in a cluster

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🟢 4️⃣ Example: Deploy a .NET Core API to Kubernetes

Step 1: Dockerize Your .NET Core App

• Create Dockerfile and build image as explained earlier.

Step 2: Push Docker Image to Registry

docker tag mywebapi:1.0 mydockerhubuser/mywebapi:1.0
docker push mydockerhubuser/mywebapi:1.0

Step 3: Create Kubernetes Deployment

deployment.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: mywebapi-deployment
spec:
  replicas: 3
  selector:
    matchLabels:
      app: mywebapi
  template:
    metadata:
      labels:
        app: mywebapi
    spec:
      containers:
      - name: mywebapi
        image: mydockerhubuser/mywebapi:1.0
        ports:
        - containerPort: 80

• replicas: number of pods (instances) to run.

Step 4: Expose the Deployment as a Service

service.yaml

apiVersion: v1
kind: Service
metadata:
  name: mywebapi-service
spec:
  type: LoadBalancer
  selector:
    app: mywebapi
  ports:
    - protocol: TCP
      port: 80
      targetPort: 80

• LoadBalancer exposes your API to the outside world.

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Step 5: Apply Config to Cluster

kubectl apply -f deployment.yaml
kubectl apply -f service.yaml

• Check pods: kubectl get pods

• Check services: kubectl get svc

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🟢 5️⃣ How Microservices Work on Kubernetes

• Each microservice runs in its own deployment + pods.

• Services communicate internally via Kubernetes Service (DNS name).

• Messages/events can be processed asynchronously using message queues (RabbitMQ, Kafka).

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🟢 6️⃣ Benefits for .NET Core Apps

1. Easy to scale APIs or background workers independently.

2. Can run cross-platform containers (.NET Core works on Linux).

3. Automatic updates and self-healing reduce downtime.

4. Supports microservices architecture with multiple small services.

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🟢 7️⃣ Quick Summary

• Docker: packages app into container

• Kubernetes: manages many containers automatically

• .NET Core + Docker + K8s → scalable, resilient microservices architecture