Solution

In the votingapp directory, replace each Pod specification with a Deployment specification with a single replica. Name these Deployment files deploy-XXX.yaml where XXX is the name of the microservice (voteui, vote, …)

apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: vote-ui
  name: vote-ui
spec:
  replicas: 1
  selector:
    matchLabels:
      app: vote-ui
  template:
    metadata:
      labels:
        app: vote-ui
    spec:
      containers:
        - image: voting/vote-ui:latest
          name: vote-ui

apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: vote
  name: vote
spec:
  replicas: 1
  selector:
    matchLabels:
      app: vote
  template:
    metadata:
      labels:
        app: vote
    spec:
      containers:
        - image: voting/vote:latest
          name: vote

apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: redis
  name: redis
spec:
  replicas: 1
  selector:
    matchLabels:
      app: redis
  template:
    metadata:
      labels:
        app: redis
    spec:
      containers:
        - image: redis:7.0.8-alpine3.17
          name: redis

apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: worker
  name: worker
spec:
  replicas: 1
  selector:
    matchLabels:
      app: worker
  template:
    metadata:
      labels:
        app: worker
    spec:
      containers:
        - image: voting/worker:latest
          name: worker

apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: db
  name: db
spec:
  replicas: 1
  selector:
    matchLabels:
      app: db
  template:
    metadata:
      labels:
        app: db
    spec:
      containers:
        - image: postgres:15.1-alpine3.17
          name: postgres
          env:
            - name: POSTGRES_PASSWORD
              value: postgres
          ports:
            - containerPort: 5432
              name: postgres

apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: result
  name: result
spec:
  replicas: 1
  selector:
    matchLabels:
      app: result
  template:
    metadata:
      labels:
        app: result
    spec:
      containers:
        - image: voting/result:latest
          name: result

apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: result-ui
  name: result-ui
spec:
  replicas: 1
  selector:
    matchLabels:
      app: result-ui
  template:
    metadata:
      labels:
        app: result-ui
    spec:
      containers:
        - image: voting/result-ui:latest
          name: result-ui

Deploy the application with the following command from the votingapp directory:

kubectl apply -f .

As before, using the IP address of one of the cluster nodes, you can access the vote and result interfaces via ports 31000 and 31001 respectively.

Vote

Results

Each Pod is now managed by a Deployment. If a Pod is deleted, another Pod is automatically created to replace it.

List of Pods:

$ kubectl get po
NAME                         READY   STATUS    RESTARTS   AGE
db-647c8f548b-j7z79          1/1     Running   0          3m35s
redis-6f95f75d56-7gwjz       1/1     Running   0          3m35s
result-7f897b4d58-qqtt4      1/1     Running   0          3m35s
result-ui-5cdd74d999-q5tx7   1/1     Running   0          3m34s
vote-6c847fd45-fpprh         1/1     Running   0          3m35s
vote-ui-74849dd9b4-gwcq9     1/1     Running   0          3m35s
worker-8655654586-k44vw      1/1     Running   0          3m35s

Deleting a Pod (e.g., worker):

$ kubectl delete po worker-8655654586-k44vw 
pod "worker-8655654586-k44vw" deleted

A new Pod is automatically launched to replace the one that was deleted.

$ kubectl get po                                 
NAME                         READY   STATUS    RESTARTS   AGE
db-647c8f548b-j7z79          1/1     Running   0          5m15s
redis-6f95f75d56-7gwjz       1/1     Running   0          5m15s
result-7f897b4d58-qqtt4      1/1     Running   0          5m15s
result-ui-5cdd74d999-q5tx7   1/1     Running   0          5m14s
vote-6c847fd45-fpprh         1/1     Running   0          5m15s
vote-ui-74849dd9b4-gwcq9     1/1     Running   0          5m15s
worker-8655654586-mmzgh      1/1     Running   0          4s

A Deployment ensures that Pods are always present. If we had deleted a Pod that was not managed by a Deployment (a Naked Pod), no new Pod would be automatically created to replace it.

We delete the application with the following command:

kubectl delete -f .