Run and Operate It

Visit, scale, update, roll back.

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A running application is only the beginning. Now we operate it. We visit it, scale it up for a busy day, ship a new version, and undo a mistake. The same moves you will make every week in real life.

Visit the shop
Scale for a busy day
Update and roll back

Visiting the shop

Let's visit. We open a tunnel to the ingress controller, and send requests, with the host name, shop dot local. The root path returns the web page, from our config map. The slash A P I path returns the message of the A P I. Two services, behind one front door. That is a working application.

kubectl

kubectl port-forward -n ingress-nginx svc/ingress-nginx-controller 8081:80
tunnel ready
curl -s -H 'Host: shop.local' localhost:8081/
<h1>Welcome to the Shop</h1>
curl -s -H 'Host: shop.local' localhost:8081/api
Shop API is running

File used: 01-data.yaml

apiVersion: v1
kind: Namespace
metadata:
  name: shop
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: redis
  namespace: shop
spec:
  replicas: 1
  selector:
    matchLabels:
      app: redis
  template:
    metadata:
      labels:
        app: redis
    spec:
      containers:
      - name: redis
        image: redis:7-alpine
        ports:
        - containerPort: 6379
---
apiVersion: v1
kind: Service
metadata:
  name: redis
  namespace: shop
spec:
  selector:
    app: redis
  ports:
  - port: 6379

File used: 02-api.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: api
  namespace: shop
spec:
  replicas: 2
  selector:
    matchLabels:
      app: api
  template:
    metadata:
      labels:
        app: api
    spec:
      containers:
      - name: api
        image: hashicorp/http-echo:1.0
        args: ["-text=Shop API is running"]
        ports:
        - containerPort: 5678
        readinessProbe:
          httpGet:
            path: /
            port: 5678
        resources:
          requests:
            cpu: 50m
            memory: 32Mi
          limits:
            memory: 64Mi
---
apiVersion: v1
kind: Service
metadata:
  name: api
  namespace: shop
spec:
  selector:
    app: api
  ports:
  - port: 80
    targetPort: 5678

File used: 03-web.yaml

apiVersion: v1
kind: ConfigMap
metadata:
  name: web-html
  namespace: shop
data:
  index.html: "<h1>Welcome to the Shop</h1>"
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: web
  namespace: shop
spec:
  replicas: 2
  selector:
    matchLabels:
      app: web
  template:
    metadata:
      labels:
        app: web
    spec:
      containers:
      - name: web
        image: nginx:1.27
        volumeMounts:
        - name: html
          mountPath: /usr/share/nginx/html
      volumes:
      - name: html
        configMap:
          name: web-html
---
apiVersion: v1
kind: Service
metadata:
  name: web
  namespace: shop
spec:
  selector:
    app: web
  ports:
  - port: 80

File used: 04-ingress.yaml

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: shop
  namespace: shop
spec:
  ingressClassName: nginx
  rules:
  - host: shop.local
    http:
      paths:
      - path: /api
        pathType: Prefix
        backend:
          service:
            name: api
            port:
              number: 80
      - path: /
        pathType: Prefix
        backend:
          service:
            name: web
            port:
              number: 80

Scale and update

Now, a busy day. We scale the A P I to four replicas, with one command, and list the pods. Four pods, spread over the nodes. Next, a new release of the web tier. We change its image, which starts a rolling update, and wait for it to finish. The shop stays online, throughout. And finally, imagine the new version is bad. One command, rollout undo, returns to the previous version. You have just run a deployment, as a professional.

kubectl

kubectl scale deployment api -n shop --replicas=4
deployment.apps/api scaled
kubectl get pods -n shop -l app=api
NAME                  READY   STATUS    RESTARTS   AGE
api-7f887f48b-9plqj   1/1     Running   0          39s
api-7f887f48b-db9gp   1/1     Running   0          10s
api-7f887f48b-gk9hg   1/1     Running   0          10s
api-7f887f48b-zfbzp   1/1     Running   0          39s
kubectl set image deployment/web web=nginx:1.25 -n shop
deployment.apps/web image updated
kubectl rollout status deployment/web -n shop
Waiting for deployment "web" rollout to finish: 1 out of 2 new replicas have been updated...
Waiting for deployment "web" rollout to finish: 1 old replicas are pending termination...
deployment "web" successfully rolled out
kubectl rollout undo deployment/web -n shop
deployment.apps/web rolled back

File used: 01-data.yaml

apiVersion: v1
kind: Namespace
metadata:
  name: shop
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: redis
  namespace: shop
spec:
  replicas: 1
  selector:
    matchLabels:
      app: redis
  template:
    metadata:
      labels:
        app: redis
    spec:
      containers:
      - name: redis
        image: redis:7-alpine
        ports:
        - containerPort: 6379
---
apiVersion: v1
kind: Service
metadata:
  name: redis
  namespace: shop
spec:
  selector:
    app: redis
  ports:
  - port: 6379

File used: 02-api.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: api
  namespace: shop
spec:
  replicas: 2
  selector:
    matchLabels:
      app: api
  template:
    metadata:
      labels:
        app: api
    spec:
      containers:
      - name: api
        image: hashicorp/http-echo:1.0
        args: ["-text=Shop API is running"]
        ports:
        - containerPort: 5678
        readinessProbe:
          httpGet:
            path: /
            port: 5678
        resources:
          requests:
            cpu: 50m
            memory: 32Mi
          limits:
            memory: 64Mi
---
apiVersion: v1
kind: Service
metadata:
  name: api
  namespace: shop
spec:
  selector:
    app: api
  ports:
  - port: 80
    targetPort: 5678

File used: 03-web.yaml

apiVersion: v1
kind: ConfigMap
metadata:
  name: web-html
  namespace: shop
data:
  index.html: "<h1>Welcome to the Shop</h1>"
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: web
  namespace: shop
spec:
  replicas: 2
  selector:
    matchLabels:
      app: web
  template:
    metadata:
      labels:
        app: web
    spec:
      containers:
      - name: web
        image: nginx:1.27
        volumeMounts:
        - name: html
          mountPath: /usr/share/nginx/html
      volumes:
      - name: html
        configMap:
          name: web-html
---
apiVersion: v1
kind: Service
metadata:
  name: web
  namespace: shop
spec:
  selector:
    app: web
  ports:
  - port: 80

File used: 04-ingress.yaml

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: shop
  namespace: shop
spec:
  ingressClassName: nginx
  rules:
  - host: shop.local
    http:
      paths:
      - path: /api
        pathType: Prefix
        backend:
          service:
            name: api
            port:
              number: 80
      - path: /
        pathType: Prefix
        backend:
          service:
            name: web
            port:
              number: 80

What you practised

Look at what this small shop used. Namespaces, deployments, services, a config map, probes, resource requests, an ingress, scaling, rolling updates, and rollbacks. Real production systems add more, secrets, storage, autoscaling, policies, monitoring, and Git ops, but the foundation is the same. If you can build and operate this shop confidently, you can learn the rest quickly.

Namespaces and workloadsstructure

Services and ingressconnections

Config and probesbehaviour

Scale, update, rollbackoperations

Summary

Excellent. You planned, built, ran, scaled, updated, and rolled back a complete application. That is the real skill. Next, a short quiz, to check what you remember, and tips for certification.

Key takeaways

Plan, build in layers
Visit, scale, update
Roll back mistakes

Next up: Quiz Time — test your knowledge

❮ Build It Layer by Layer Quiz Time: The Foundations ❯