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Scaling_and_Rolling_Updates

Scaling and Rolling Updates​

To scale a deployment:

kubectl scale deploy/dev-web --replicas=4

To trigger a rolling update, we can change the image of a container:

kubectl edit deployment nginx

...
containers:
  - image: nginx: 1.8 # change to older value
...

Rollbacks​

using the --record option of the kubectl create command, which allows annotation in the resource definition.

kubectl create deploy ghost --image=ghost --record

$ kubectl get deployments ghost -o yaml
deployment.kubernetes.io/revision: "1" 
kubernetes.io/change-cause: kubectl create deploy ghost --image=ghost --record

Should an update fail, due to an improper image version, for example, you can roll back the change to a working version with kubectl rollout undo:

kubectl set image deployment/ghost ghost=ghost:09 --all

kubectl rollout history deployment/ghost deployments "ghost":
REVISION   CHANGE-CAUSE
1 ​         kubectl create deploy ghost --image=ghost --record
2          kubectl set image deployment/ghost ghost=ghost:09 --all

kubectl get pods
NAME                    READY  STATUS            RESTARTS  AGE
ghost-2141819201-tcths  0/1    ImagePullBackOff  0         1m​

kubectl rollout undo deployment/ghost ; kubectl get pods

NAME                    READY  STATUS   RESTARTS  AGE
ghost-3378155678-eq5i6  1/1    Running  0         7s

You can roll back to a specific revision with the --to-revision=2 option.

You can also edit a Deployment using the kubectl edit command.

You can also pause a Deployment, and then resume.

kubectl rollout pause deployment/ghost

kubectl rollout resume deployment/ghost

Can still do a rolling update on ReplicationControllers with the kubectl rolling-update command, but this is done on the client side. Hence, if you close your client, the rolling update will stop.