Docker Kubernetes Introduction

An introduction to Kubernetes as a container orchestration platform.

Basic Kubernetes Concepts

Pod

# A Pod is the smallest unit in Kubernetes
apiVersion: v1
kind: Pod
metadata:
  name: api-pod
spec:
  containers:
  - name: api
    image: myapp:1.0
    ports:
    - containerPort: 3000

Deployment

# A Deployment manages replicaset
apiVersion: apps/v1
kind: Deployment
metadata:
  name: api-deployment
spec:
  replicas: 3
  selector:
    matchLabels:
      app: api
  template:
    metadata:
      labels:
        app: api
    spec:
      containers:
      - name: api
        image: myapp:1.0
        ports:
        - containerPort: 3000

Service

# A Service provides access to pods
apiVersion: v1
kind: Service
metadata:
  name: api-service
spec:
  selector:
    app: api
  ports:
  - port: 80
    targetPort: 3000
  type: LoadBalancer

Use Case: Application on K8s

# deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: myapp-api
spec:
  replicas: 3
  selector:
    matchLabels:
      app: myapp-api
  template:
    metadata:
      labels:
        app: myapp-api
    spec:
      containers:
      - name: api
        image: myapp-api:1.0
        ports:
        - containerPort: 3000
        env:
        - name: DB_HOST
          value: "database-service"
        - name: DB_PASSWORD
          valueFrom:
            secretKeyRef:
              name: db-secret
              key: password

# Deploy to Kubernetes
kubectl apply -f deployment.yaml

# View pods
kubectl get pods

# View deployments
kubectl get deployments

# View services
kubectl get services

Docker Swarm vs Kubernetes

Everyday Use Case

Case: A developer needs to deploy an application to Kubernetes.

# Build the image
docker build -t myapp-api:1.0 .

# Push to the registry
docker push registry.myapp.local/myapp-api:1.0

# Deploy to K8s
kubectl apply -f k8s/

# Check the status
kubectl get pods
kubectl get services

Best Practices

1. Use Helm charts: For packaging
2. ConfigMaps and Secrets: For configuration
3. Resource limits: Set CPU and memory
4. Health checks: Liveness and readiness probes
5. Rolling updates: For zero-downtime deployments

Conclusion

Kubernetes is a powerful orchestration platform. For complex applications, Kubernetes provides greater flexibility and scalability.