Rolling Updates in Kunbernetes

 Task:

We have an application running on Kubernetes cluster using nginx web server. The Nautilus application development team has pushed some of the latest features to prod branch and those need be deployed. The Nautilus DevOps team has created an image nginx:1.18 with latest changes.

Perform a rolling update for this application and incorporate nginx:1.18 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.

Step 1) Check if the deployment nginx-deployment is present

thor@jump_host ~$ kubectl get deployment 

NAME               READY   UP-TO-DATE   AVAILABLE   AGE

nginx-deployment   3/3     3            3           8m19s

Step 2) Check if the pods are running

thor@jump_host ~$ kubectl get pods

NAME                                READY   STATUS    RESTARTS   AGE

nginx-deployment-74fb588559-7447s   1/1     Running   0          8m37s

nginx-deployment-74fb588559-ch6mm   1/1     Running   0          8m37s

nginx-deployment-74fb588559-g9cm7   1/1     Running   0          8m37s

Step 3) Check what deployment version is running on the container

thor@jump_host ~$ kubectl get deployment -o wide

NAME               READY   UP-TO-DATE   AVAILABLE   AGE     CONTAINERS        IMAGES       SELECTOR

nginx-deployment   3/3     3            3           8m56s   nginx-container   nginx:1.16   app=nginx-app

Step 4) Update the image version to nginx:1.18 from nginx:1.16

thor@jump_host ~$ kubectl set image deployment/nginx-deployment nginx-container=nginx:1.18 --record=true

deployment.apps/nginx-deployment image updated

Step 5)  Check the status of the pods and wait until they come back to running state

thor@jump_host ~$ kubectl get pods 

NAME                                READY   STATUS              RESTARTS   AGE

nginx-deployment-74fb588559-7447s   1/1     Running             0          14m

nginx-deployment-74fb588559-ch6mm   0/1     Terminating         0          14m

nginx-deployment-74fb588559-g9cm7   1/1     Running             0          14m

nginx-deployment-7b6877b9b5-6qcw6   0/1     ContainerCreating   0          2s

nginx-deployment-7b6877b9b5-l8v6c   1/1     Running             0          9s

thor@jump_host ~$ kubectl get pods

NAME                                READY   STATUS    RESTARTS   AGE

nginx-deployment-7b6877b9b5-6qcw6   1/1     Running   0          46s

nginx-deployment-7b6877b9b5-776br   1/1     Running   0          44s

nginx-deployment-7b6877b9b5-l8v6c   1/1     Running   0          53s

thor@jump_host ~$ kubectl get pods -o wide

NAME                                READY   STATUS    RESTARTS   AGE    IP           NODE     NOMINATED NODE   READINESS GATES

nginx-deployment-7b6877b9b5-6qcw6   1/1     Running   0          109s   10.244.1.7   node01   <none>           <none>

nginx-deployment-7b6877b9b5-776br   1/1     Running   0          107s   10.244.1.8   node01   <none>           <none>

nginx-deployment-7b6877b9b5-l8v6c   1/1     Running   0          116s   10.244.1.6   node01   <none>           <none>

Step 6) Check the rollout history 

thor@jump_host ~$ kubectl rollout history deployment 

deployment.apps/nginx-deployment 

REVISION  CHANGE-CAUSE

1         <none>

2         kubectl set image deployment/nginx-deployment nginx-container=nginx:1.18 --record=true

Step 7) Check the image version now

thor@jump_host ~$ kubectl get deployment -o wide

NAME               READY   UP-TO-DATE   AVAILABLE   AGE   CONTAINERS        IMAGES       SELECTOR

nginx-deployment   3/3     3            3           16m   nginx-container   nginx:1.18   app=nginx-app