ReplicaSets with YAML

Step-01: Create ReplicaSet Definition

• replicaset-definition.yml

apiVersion: apps/v1
kind: ReplicaSet
metadata:
  name: myapp2-rs
spec:
  replicas: 3 # 3 Pods should exist at all times.
  selector:  # Pods label should be defined in ReplicaSet label selector
    matchLabels:
      app: myapp2
  template:
    metadata:
      name: myapp2-pod
      labels:
        app: myapp2 # Atleast 1 Pod label should match with ReplicaSet Label Selector
    spec:
      containers:
      - name: myapp2
        image: stacksimplify/kubenginx:2.0.0
        ports:
          - containerPort: 80

Step-02: Create ReplicaSet

• Create ReplicaSet with 3 Replicas

# Create ReplicaSet
kubectl apply -f 02-replicaset-definition.yml

# List Replicasets
kubectl get rs

• Delete a pod
• ReplicaSet immediately creates the pod.

# List Pods
kubectl get pods

# Delete Pod
kubectl delete pod <Pod-Name>

Step-03: Create NodePort Service for ReplicaSet

apiVersion: v1
kind: Service
metadata:
  name: replicaset-nodeport-service
spec:
  type: NodePort
  selector:
    app: myapp2
  ports:
    - name: http
      port: 80
      targetPort: 80
      nodePort: 31232  

• Create NodePort Service for ReplicaSet & Test

# Create NodePort Service
kubectl apply -f 03-replicaset-nodeport-servie.yml

# List NodePort Service
kubectl get svc

# Get Public IP
kubectl get nodes -o wide

# Access Application
http://<Worker-Node-Public-IP>:<NodePort>
http://<Worker-Node-Public-IP>:31232

API References

• ReplicaSet: https://kubernetes.io/docs/reference/generated/kubernetes-api/v1.18/#replicaset-v1-apps