[Question] Should commonLabels be patchable? I ran into kind of a show stopper

[nickjj]

Imagine a typical set up by having this in 1 overlay directory with a kustomization.yaml file that inherits from a base:

• Deployment for a web app
• Service for the web app
• Ingress for the web app
• Config map for the web app

If you wanted to add a common app.kubernetes.io/name: "hello-app" label to all of these this is no problem, you can use commonLabels and you're good to go.

Then you can patch things as needed to do whatever else you need to do in your overlays.

But now let's say you want to introduce a "Background worker deployment". It would be essentially a duplicate of the web app deployment except with a different name. You'd also likely add a patch to override the image's command and a replace patch for the health checks. It would use the same config map and secrets as the web app deployment.

If you're using something like the AWS load balancer controller, it'll try to attach a load balancer readiness gate to the background worker because one criteria it uses is to attach it to pods whose name label matches a service. That will cause the background worker to fail and never become healthy because it's not a web service.

A solution for this would be to ensure the background worker has a different name label but how can we do that if commonLabels can't be removed or patched?

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[nickjj]

Technically you can solve this with #1009 (comment), thanks a lot for that @zhouhaibing089!

I tested that for both remove and replace and it works. You can modify both labels and selectors. For anyone reading this in the future, selectors are immutable which will fail to apply if you try to rename them in an existing deployment.

If you delete your old deployment and then apply this type of patch it will work. Future deploys will also work as long as you're not renaming the selector again.