Feature flagging for exporting of Kanister prometheus metrics

[mellon-collie]

Change Overview

Adding a new helm flag and environment variable for feature toggling of the new Kanister prometheus metrics integration.

1. Added new boolean helm flag called controller.metrics.enabled in the Values.yaml
2. Added new environment variable called KANISTER_METRICS_ENABLED in deployment.yaml to capture the metrics.enabled flag in our codebase.

End goal: In order to switch on prometheus metrics, the end user can install the local helm chart with the following command:
helm install kanister ./helm/kanister-operator \ --create-namespace \ --namespace kanister \ --set image.repository=<your_registry>/<your_controller_image> \ --set image.tag=<your_image_tag> --controller.metrics.enabled=true

Pull request type

Please check the type of change your PR introduces:

• 🚧 Work in Progress
• 🌈 Refactoring (no functional changes, no api changes)
• 🐹 Trivial/Minor
• 🐛 Bugfix
• 🌻 Feature
• 🗺️ Documentation
• 🤖 Test

Issues

• fixes N/A

Test Plan

After the above changes were made, the following tests were performed:

1. helm uninstall kanister -n kanister to uninstall existing kanister deployment
2. helm install kanister ./helm/kanister-operator --create-namespace --namespace kanister to run the local helm chart for kanister
3. k get pods -n kanister to identify the new kanister operator pod that's running
4. kubectl exec -n kanister -it <pod-name> -- /bin/bash to exec into the pod.
5. echo $KANISTER_METRICS_ENABLED - the output should be a false.

• 💪 Manual
• ⚡ Unit test
• 💚 E2E

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[pavannd1]

Should we add this as a sub-value under controller above? Open to suggestions @viveksinghggits
Additionally, add a comment

[mellon-collie]

Sure. Makes sense. I've made it as a sub-value under controller. I've added a comment.
One more point - I'm maintaining two levels of hierarchy for the helm flags - like metrics.enabled instead of metrics_enabled because we may want to add more flags under metrics hierarchy in the future if we consider adding labels for a new metric partially.

[pavannd1]

Yes, that's the right way to do it 👍🏼

[viveksinghggits]

do we just want to set the env var in the pod as part of this PR? Do we not want to use it anywhere?

[mellon-collie]

@viveksinghggits Yes. The feature flag will start getting used in the next set of PRs for the metrics we export.