Automatic rolling of Pods due to configuration changes

Kubernetes
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In this post I will show you how you can for pod upgrade at config changes in helm charts.

Alongside the deployment of containers, we often ship configuration via ConfigMap and/or Secret resources. A common challenge is the need to restart the Pod resources when there is a change in the associated configuration.

By default, if the Pod itself didn’t change, the Deployment or StatefulSet resource will not trigger a new rollout.

Roll when Secret or ConfigMap resources changes

So to rol the Pod we need to change something in the spec when the config is changing. But what? and how to realize the change of the ConfigMap and/or Secret? The solution is to store the checksum of the ConfigMap and/or Secret in the annotation of the Deployment, so when the file is changing the checksum is changing too, and with this we gat a new version from the Deployment.

kind: Deployment
[...]
spec:
  template:
    metadata:
      annotations:
        checksum/config: {{ include (print $.Template.BasePath "/configmap.yaml") . | sha256sum }}
[...]

For resources defined as part of a library chart:

kind: Deployment
[...]
spec:
  template:
    metadata:
      annotations:
        checksum/config: {{ include ("mylibchart.configmap") . | sha256sum }}
[...]