WIll "helm upgrade" restart PODS even if they are not affected by upgrade?

Question

My helm chart has some 12 PODS. When I did helm upgrade after changing some values all the PODs are restarted except for one.

My question is:

Will helm upgrade restart the PODS even if they are not affected by upgrade?

Putting it in another way:

Is it helm upgrade restart PODs only if they are affected by upgrade?

Answer 1

The flag --recreate-pods was marked as deprecated in Helm 2 and was removed with Helm 3.

Helm suggests to either add checksums of other files which could have changed like this

      annotations:
        checksum/config: {{ include (print $.Template.BasePath "/configmap.yaml") . | sha256sum }}

or to add an annotation with a random number which forces an update on each rollout:

      annotations:
        rollme: {{ randAlphaNum 5 | quote }}

See Helm docs: https://v3.helm.sh/docs/howto/charts_tips_and_tricks/#automatically-roll-deployments

Answer 2

As far as I am concerned helm restart only the pods which are affected by upgrade

If You want to restart ALL pods you can use --recreate-pods flag

--recreate-pods -> performs pods restart for the resource if applicable

For example if You have dashboard chart, You can use this command to restart every pod.

helm upgrade --recreate-pods -i k8s-dashboard stable/k8s-dashboard

There is a github issue which provide another workaround for it

Every time you need to restart the pods, change the value of that annotation. A good annotation could be timestamp

First, add an annotation to the pod. If your chart is of kind Deployment, add annotation to spec.template.metadata.annotations. For example:

kind: Deployment
spec:
  template:
    metadata:
      labels:
        app: ecf-helm-satellite-qa
      annotations:
        timestamp: "{{ .Values.timestamp }}"

Deploy that. Now, every time you set timestamp in helm command. Kubernetes will rollout a new update without downtime.

helm upgrade ecf-helm-satellite-qa . --set-string timestamp=a_random_value

Answer 3

--recreate-pods has been removed in helm 3 and that certainly got the attention of some helm users.

I force the pods to be recreated using a timestamp in the deployment pod spec. Note that it has to be in the spec, this will not work at the deployment top level:

spec:
  template:
    metadata:
      annotations:
        releaseTime: {{ dateInZone "2006-01-02 15:04:05Z" (now) "UTC"| quote }}