VotingApp Deployment

This note shows how to deploy a small microservice system to Kubernetes using Deployments and Services. The application components are:

voting-app: Python Flask web app where users submit votes
redis: in-memory store used as a queue for votes
worker: background consumer that reads votes from Redis and writes to PostgreSQL
db: PostgreSQL database (stateful)
result-app: Python Flask web app that reads aggregated results from PostgreSQL

The manifests below assume you already have container images for each component (for example your-registry/voting-app:latest, your-registry/result-app:latest, etc.). Replace image names with your actual images before applying.

This demo creates a namespace, a Secret for DB credentials, a PVC for Postgres, Deployments for stateless services, a Deployment + PVC for the database, and Services to expose the components internally. For external access we expose result-app via a NodePort example and recommend adding an Ingress in production.

Namespace

apiVersion: v1
kind: Namespace
metadata:
  name: voting-demo

Secrets and Config

Create a secret for Postgres credentials (base64-encoded values or use kubectl create secret):

apiVersion: v1
kind: Secret
metadata:
  name: pg-credentials
  namespace: voting-demo
type: Opaque
data:
  POSTGRES_USER: cG9zdGdyZXM= # base64 for 'postgres'
  POSTGRES_PASSWORD: c2VjcmV0 # base64 for 'secret'
  POSTGRES_DB: dm90aW5n # base64 for 'voting'

Alternatively create secret from literals:

kubectl -n voting-demo create secret generic pg-credentials \
  --from-literal=POSTGRES_USER=postgres \
  --from-literal=POSTGRES_PASSWORD=secret \
  --from-literal=POSTGRES_DB=voting

PersistentVolumeClaim for Postgres

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: pg-data
  namespace: voting-demo
spec:
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 5Gi

Note: On cloud providers this will dynamically provision a PV. For local clusters (kind/minikube), ensure a storage class is available or use hostPath for demos.

PostgreSQL Deployment

apiVersion: apps/v1
kind: Deployment
metadata:
  name: postgres
  namespace: voting-demo
spec:
  replicas: 1
  selector:
    matchLabels:
      app: postgres
  template:
    metadata:
      labels:
        app: postgres
    spec:
      containers:
        - name: postgres
          image: postgres:15
          env:
            - name: POSTGRES_USER
              valueFrom:
                secretKeyRef:
                  name: pg-credentials
                  key: POSTGRES_USER
            - name: POSTGRES_PASSWORD
              valueFrom:
                secretKeyRef:
                  name: pg-credentials
                  key: POSTGRES_PASSWORD
            - name: POSTGRES_DB
              valueFrom:
                secretKeyRef:
                  name: pg-credentials
                  key: POSTGRES_DB
          ports:
            - containerPort: 5432
          volumeMounts:
            - name: pg-data
              mountPath: /var/lib/postgresql/data
      volumes:
        - name: pg-data
          persistentVolumeClaim:
            claimName: pg-data

Create a Service for Postgres (ClusterIP):

apiVersion: v1
kind: Service
metadata:
  name: postgres
  namespace: voting-demo
spec:
  ports:
    - port: 5432
      targetPort: 5432
  selector:
    app: postgres
  type: ClusterIP

Redis Deployment + Service

Redis will be used as a simple queue for votes.

apiVersion: apps/v1
kind: Deployment
metadata:
  name: redis
  namespace: voting-demo
spec:
  replicas: 1
  selector:
    matchLabels:
      app: redis
  template:
    metadata:
      labels:
        app: redis
    spec:
      containers:
        - name: redis
          image: redis:7
          ports:
            - containerPort: 6379

---
apiVersion: v1
kind: Service
metadata:
  name: redis
  namespace: voting-demo
spec:
  selector:
    app: redis
  ports:
    - port: 6379
      targetPort: 6379
  type: ClusterIP