Kubernetes Rolling update / restart without changing the version of pods

With the default kubernetes we cannot maintain rolling update while keeping the same container version but there is a workaround for this,

This can be done by adding a patch label to the deployment. Once the patch updated, pods getting rolling restart by pulling images,

$ kubectl patch deployment <your deployment name> -p '{"spec":{"template":{"spec":{"containers":[{"name":"<your container name","env":[{"name":"LAST_ROLLOUT","value":"'$(date +%s)'"}]}]}}}}'

You can test your deployment in kubernetes for the new label,

$ kubectl.exe get deployment <your deployment name> -o yaml

spec:

  template:

...

    spec:

      containers:

      - env:

        - name: LAST_ROLLOUT

          value: "1553772196"

       

You can get pods list to check whether new ones created and existing ones terminated,

$ kubectl.exe get pods

NAME                                           READY     STATUS             RESTARTS   AGE

test-776885db4c-rdb6j                  2/2       Running            0          5h

test-84fdbf5cc8-wv4qv                  0/2       PodInitializing    0          4s

$ kubectl.exe get pods

NAME                                           READY     STATUS             RESTARTS   AGE

test-776885db4c-rdb6j                  0/2       Terminating        0          5h

test-84fdbf5cc8-wv4qv                  2/2       Running              1          40s

Now you can check rollout status using below command,

$ kubectl.exe rollout status deployment <your deployment name>

deployment "<your deployment name>" successfully rolled out

Also you can check rollout history by using below command,

$ kubectl.exe rollout history deployment <your deployment name>

deployments "<your deployment name>"

REVISION  CHANGE-CAUSE

1         kubectl.exe patch deployment <your deployment name> --patch={"spec":{"template":{"spec":{"containers":[{"name":"<your deployment name>","env":[{"name":"LAST_ROLLOUT","value":"1553772196"}]}]}}}}

You can use below commands to undo roll outs,

Undo to previous deployment,

$ kubectl rollout undo deployment <your deployment name>

Undo to a specific roll out revision,

$ kubectl rollout undo deployment <deployment> --to-revision=<revision Number that you get from rollout history command (1,2,…)>

References,

https://github.com/kubernetes/kubernetes/issues/13488

https://github.com/kubernetes/kubernetes/issues/27081