CRD (Custom Resource Definitions) & Operators

• Kubernetes gives the extension mechanism where we create
  • CRD (Custom resource definition)
  • Operators: Refer Here
    • They create reconcile loop
• Lifecycle => CRD + Operator

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Problem 1: Static YAML Manifests

• K8s manifests are static in nature
• During deployments we will have changes to handle
  • image tags
  • labels
  • namespaces
• We have to manually change the manifests

Problem 2: No Reusability

• Manifest YAML files are not reusable

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Solutions

1. Helm:
2. This works as a package manager to kubernetes
3. we need to install helm
4. Kustomize:
5. This works as if manages multiple environments
6. This works with native kubectl

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Helm

• Refer Here for official docs and Refer Here to install helm
• In helm
  
• Components:
  • Helm (client)
  • Repository (Which hosts the charts)
  • Chart (An individual package)

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Create a helm chart for basic deployment

• YAML Manifest

---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx
spec:
  replicas: 3
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx:1.27
        resources:
          limits:
            memory: "128Mi"
            cpu: "500m"
        ports:
        - containerPort: 80
---
apiVersion: v1
kind: Service
metadata:
  name: nginx-svc
spec:
  type: ClusterIP
  selector:
    app: nginx
  ports:
  - port: 80
    targetPort: 80

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Helm Charts

• Lets create a helm chart

helm create activity1

• A folder called as activity1 is create with following content
  
• Refer Here for official docs on Charts
• Helm use go templating syntax Refer Here
• Use helm online validator to verify expression Refer Here
• Helm creates manifests and passes it to the kubectl after replacing dynamic expression (template expressions)
  
• Refer Here for synaxes used in Helm
• Refer Here for the helm chart.
• Now create a chart repository and push the chart to repository

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Kustomize

• Kustomize simplifies templating without strange expressions
• Refer Here for official docs
• Refer Here for kustomize documents
• Refer Here
• Refer Here for multi base

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Elastic Kubernetes Service (EKS)

• This is kubernetes as a service offering from AWS
• AWS Service Integrations: (Private integrations)
  • AWS has VPC CNI where every pod gets an ip address from vpc range
  • AWS services can be linked to AWS load Balancers
  • AWS EKS provides Application Load Balancer Ingress controller
  • AWS EKS provides necessary CSI implementations (StorageClasses) to use
    • AWS EBS Disks
    • AWS EFS
    • AWS FSx
    • AWS S3
• EKS offers cluster node autoscaling
  • Cluster autoscaler
  • Karpenter
• EKS can be integrated with IAM to bring in AWS users or with external identity servers
• What are different EKS offerings ?
  • EKS (Completely on AWS)
    • Compute options
      • EC2
      • Fargate
  • EKS on Outposts (Hybrid cloud)
  • EKS Anywhere (distribution)
    • Onprem
• EKS creation options
  • Console
  • cli
  • eksctl Refer Here
  • terraform (CI/CD)