[bitnami/thanos] support using an existing PVC for Thanos Ruler rules config files

[jessebot]

Name and Version

bitnami/thanos 15.9.2

What is the problem this feature will solve?

Right now, it is required that users of Thanos Ruler via the bitnami Thanos helm chart provide either of:

• ruler.config (a string)
• ruler.existingConfigmap (a configmap)

This assumes users want to provide their rules via a single ConfigMap or secret. I use the kiwigrid/k8s-sidecar sidecar container to automatically grab ConfigMaps matching a specific label and load them into a specific directory for Thanos Ruler to pick up. (This is similar to the same offering by Grafana for automatically detecting new Dashboards) Because of this, I can't provide either a ConfigMap nor the config string.

What is the feature you are proposing to solve the problem?

I'd like to see something like ruler.existingConfigClaim to allow using a persistent volume that both the Thanos ruler container and the side car container can mount. This would allow also for an initContainer to run before the ruler and populate the /config/rules directory. When combined with #31377 this can allow full self service of creating additional alerting rules, instead of having it centrally managed and overloading a specific team or team member to handle updates to one giant ConfigMap.

In the values.yaml, it could look like this:

ruler:
  ## @param ruler.existingConfigClaim provide an existing persistent volume claim to mount for the ruler's rules
  existingConfigClaim: ""

For reference, the ruler config is currently required to be a single config map here:

charts/bitnami/thanos/templates/ruler/statefulset.yaml

Lines 261 to 262 in 7432a31

	configMap:
	name: {{ include "thanos.ruler.configmapName" . }}

This would need to be changed to allow something like:

        - name: ruler-config
          {{- if and .Values.ruler.existingConfigClaim (not .Values.ruler.config) (not .Values.ruler.existingConfigmap) }}
          persistentVolumeClaim:
            claimName: {{ .Values.ruler.existingConfigClaim }}
          {{- else }}
          configMap:
            name: {{ include "thanos.ruler.configmapName" . }}
          {{- end }}

I can work on this PR later today.

What alternatives have you considered?

No response

[carrodher]

Thank you for bringing this issue to our attention. We appreciate your involvement! If you're interested in contributing a solution, we welcome you to create a pull request. The Bitnami team is excited to review your submission and offer feedback. You can find the contributing guidelines here.

Your contribution will greatly benefit the community. Feel free to reach out if you have any questions or need assistance.