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TASK 85: Rolling Updates in Kubernetes

Requirements​

We have an application running on Kubernetes cluster using nginx web server. The Nautilus application development team has pushed some of the latest changes and those changes need be deployed. The Nautilus DevOps team has created an image nginx:1.19 with the latest changes.

  • Perform a rolling update for this application and incorporate nginx:1.19 image. The deployment name is nginx-deployment

  • Make sure all pods are up and running after the update.

Note: The kubectl utility on jump_host has been configured to work with the kubernetes cluster.

Note

This document focuses on the implementation approach. The task statement in Requirements is preserved as the source requirement.

Prerequisites​

  • Access to the configured Kubernetes cluster from jump_host.
  • kubectl is configured and points to the correct context.
  • Use the task-specified namespace, resource names, and images exactly.

Steps​

Check all the running resources.

$ kubectl get all

NAME                                    READY   STATUS    RESTARTS   AGE
pod/nginx-deployment-74fb588559-8fcft   1/1     Running   0          53s
pod/nginx-deployment-74fb588559-gnccx   1/1     Running   0          53s
pod/nginx-deployment-74fb588559-mgqvm   1/1     Running   0          53s

NAME                    TYPE        CLUSTER-IP     EXTERNAL-IP   PORT(S)        AGE
service/kubernetes      ClusterIP   10.96.0.1      <none>        443/TCP        89m
service/nginx-service   NodePort    10.96.86.197   <none>        80:30008/TCP   53s

NAME                               READY   UP-TO-DATE   AVAILABLE   AGE
deployment.apps/nginx-deployment   3/3     3            3           53s

NAME                                          DESIRED   CURRENT   READY   AGE
replicaset.apps/nginx-deployment-74fb588559   3         3         3       53s

We can see the details of the deployment in a YAML format. Here we can see that the deployment is using a different image version.

$ kubectl get deployment nginx-deployment -o yaml

    spec:
      containers:
      - image: nginx:1.16
        imagePullPolicy: IfNotPresent
        name: nginx-container

We can change the container image using the set command.

kubectl set image deployment/nginx-deployment nginx-container=nginx:1.19

See the Pod gets updated.

watch kubectl get pods

Now check the status of the rollout update.

$ kubectl rollout status deployment nginx-deployment

deployment "nginx-deployment" successfully rolled out

To confirm, run the describe on the deployment and confirm that the container image has been updated.

$ kubectl describe deployment nginx-deployment

Name:                   nginx-deployment
Namespace:              default
CreationTimestamp:      Fri, 06 Jan 2023 08:48:49 +0000
Labels:                 app=nginx-app
                        type=front-end
Annotations:            deployment.kubernetes.io/revision: 2
Selector:               app=nginx-app
Replicas:               3 desired | 3 updated | 3 total | 3 available | 0 unavailable
StrategyType:           RollingUpdate
MinReadySeconds:        0
RollingUpdateStrategy:  25% max unavailable, 25% max surge
Pod Template:
  Labels:  app=nginx-app
  Containers:
   nginx-container:
    Image:        nginx:1.19

Verification​

  • Confirm the required pods/services/deployments/jobs are in the expected state.
  • Run kubectl get commands for the affected resource types and namespace.

Resources​