What is Kubernetes and what problems does it solve?

Kubernetes (K8s) is an open-source container orchestration platform that automates deployment, scaling, and management of containerized applications.

Problems Kubernetes Solves:

1. Container Management at Scale: Managing hundreds or thousands of containers manually is impossible
2. High Availability: Ensures applications stay running even when containers or nodes fail
3. Load Balancing: Distributes traffic across multiple container instances
4. Auto-Scaling: Automatically scales applications based on demand
5. Rolling Updates: Deploy new versions without downtime
6. Service Discovery: Containers can find and communicate with each other
7. Storage Orchestration: Manages persistent storage for stateful applications
8. Self-Healing: Automatically restarts failed containers

Kubernetes Architecture:

Control Plane Components:

• API Server: Frontend for Kubernetes control plane
• etcd: Distributed key-value store for cluster data
• Scheduler: Assigns pods to nodes
• Controller Manager: Runs controller processes

Node Components:

• Kubelet: Agent that runs on each node
• Container Runtime: Docker, containerd, etc.
• Kube-proxy: Network proxy on each node

Key Kubernetes Objects:

1. Pod - Smallest deployable unit (one or more containers)

apiVersion: v1
kind: Pod
metadata:
  name: myapi-pod
spec:
  containers:
  - name: myapi
    image: myapi:v1
    ports:
    - containerPort: 80

2. Deployment - Manages ReplicaSets and rolling updates

apiVersion: apps/v1
kind: Deployment
metadata:
  name: myapi-deployment
spec:
  replicas: 3
  selector:
    matchLabels:
      app: myapi
  template:
    metadata:
      labels:
        app: myapi
    spec:
      containers:
      - name: myapi
        image: myapi:v1
        ports:
        - containerPort: 80
        env:
        - name: ASPNETCORE_ENVIRONMENT
          value: "Production"
        resources:
          requests:
            memory: "256Mi"
            cpu: "250m"
          limits:
            memory: "512Mi"
            cpu: "500m"
        livenessProbe:
          httpGet:
            path: /health
            port: 80
          initialDelaySeconds: 30
          periodSeconds: 10
        readinessProbe:
          httpGet:
            path: /ready
            port: 80
          initialDelaySeconds: 5
          periodSeconds: 5

3. Service - Exposes pods to network traffic

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

4. ConfigMap - Stores configuration data

apiVersion: v1
kind: ConfigMap
metadata:
  name: myapi-config
data:
  appsettings.json: |
    {
      "Logging": {
        "LogLevel": {
          "Default": "Information"
        }
      }
    }

5. Secret - Stores sensitive data

apiVersion: v1
kind: Secret
metadata:
  name: myapi-secrets
type: Opaque
data:
  connectionstring: U2VydmVyPW15c3FsO0RhdGFiYXNlPW15ZGI7VXNlcj1yb290O1Bhc3N3b3JkPXBhc3M=

6. Ingress - HTTP/HTTPS routing

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: myapi-ingress
  annotations:
    kubernetes.io/ingress.class: nginx
    cert-manager.io/cluster-issuer: letsencrypt-prod
spec:
  tls:
  - hosts:
    - api.mydomain.com
    secretName: myapi-tls
  rules:
  - host: api.mydomain.com
    http:
      paths:
      - path: /
        pathType: Prefix
        backend:
          service:
            name: myapi-service
            port:
              number: 80

Common kubectl Commands:

# Deploy application
kubectl apply -f deployment.yaml

# Get resources
kubectl get pods
kubectl get deployments
kubectl get services

# Scale deployment
kubectl scale deployment myapi-deployment --replicas=5

# View logs
kubectl logs myapi-pod

# Execute command in pod
kubectl exec -it myapi-pod -- /bin/bash

# Update deployment (rolling update)
kubectl set image deployment/myapi-deployment myapi=myapi:v2

# Rollback deployment
kubectl rollout undo deployment/myapi-deployment

# Delete resources
kubectl delete -f deployment.yaml

When to Use Kubernetes:

✅ Use K8s when:

• Running microservices architecture
• Need high availability and auto-scaling
• Managing multiple environments (dev, staging, prod)
• Need container orchestration at scale

❌ Avoid K8s when:

• Simple monolithic application
• Small team with limited DevOps expertise
• Low traffic applications
• Development/testing only