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People are incorrectly assuming that using kubectl implies invoking it from an administrator's laptop. Of course, you can and should invoke kubectl from your CD

People are incorrectly assuming that using kubectl implies invoking it from an administrator's laptop. Of course, you can and should invoke kubectl from your CD pipeline. The CD pipeline maintains its own record of runs, and Kubernetes deployments have a revision history. Moreover, people in this thread also don't know what "declarative" means. The patch is declarative, and "declarative" doesn't provide the claimed benefits. For example, as with the patch command, I can create, apply, and delete a Kubernetes manifest file (indeed, I can apply directly from stdin!) and there is no additional record of the change beyond that which would exist if I had just applied the patch.

sgarland 4y ago
A patch is declarative in that it's an idempotent command which requires you to fully define the patch. It's still something that is being manually defined rather than contained in a file to be applied. Of course, if that file is just being locally held and modified on someone's laptop instead of committed to version control, it's a moot point. I will grant you that `kubectl delete -f` breaks my argument, since it's imperatively modifying objects given a declarative manifest. Re: changes via stdin, I mean sure; you can also pipe a deployment manifest into `ex` or `sed` to make changes on the fly and then echo it back to `kubectl apply -` but I wouldn't recommend it.
- throwaway894345 4y ago
  Yeah, my point is that whether you're changing a manifest and doing an apply versus a patch isn't relevant, the relevant bit is whether or not you have a version history and in both cases you do via your CD pipeline and via k8s deployment revision history. You can also commit to git, but I don't think there's much value in committing every image version change to git. Also, working in raw manifests isn't a panacea; if you delete a resource's manifest, Kubernetes won't delete its corresponding resource (maybe this is what you were referring to with your bit about `kubectl delete -f`). You need something that diffs the manifests against the current state of the world and applies the requisite patches (something like Terraform) but this isn't related to how you change image versions.
  - alias_neo 4y ago
    I agree with your points, but as I mentioned in another comment, if we take "imperative" and "declarative" as proxy terms for "I do or do not have a reference to the state I requested of the cluster OUTSIDE of the cluster"; my point is that updating the state, in full, by modifying the manifests and committing them to be deployed by your CD pipeline or otherwise is a better approach to ensuring you or someone else can rebuild your "empire" were it to unceremoniously burn to the ground.
    - throwaway894345 4y ago
      I think you’re assuming that just because we’re updating the image via kubectl (which itself is invoked via CD pipeline) that the infrastructure isn’t codified and persisted, which isn’t the case. You can (and should) still have your infrastructure manifests saved in your infra repo/directory and version controlled; that’s orthogonal to how you update the current image version.

sgarland 4y ago

A patch is declarative in that it's an idempotent command which requires you to fully define the patch. It's still something that is being manually defined rather than contained in a file to be applied. Of course, if that file is just being locally held and modified on someone's laptop instead of committed to version control, it's a moot point. I will grant you that `kubectl delete -f` breaks my argument, since it's imperatively modifying objects given a declarative manifest. Re: changes via stdin, I mean sure; you can also pipe a deployment manifest into `ex` or `sed` to make changes on the fly and then echo it back to `kubectl apply -` but I wouldn't recommend it.

throwaway894345 4y ago
Yeah, my point is that whether you're changing a manifest and doing an apply versus a patch isn't relevant, the relevant bit is whether or not you have a version history and in both cases you do via your CD pipeline and via k8s deployment revision history. You can also commit to git, but I don't think there's much value in committing every image version change to git. Also, working in raw manifests isn't a panacea; if you delete a resource's manifest, Kubernetes won't delete its corresponding resource (maybe this is what you were referring to with your bit about `kubectl delete -f`). You need something that diffs the manifests against the current state of the world and applies the requisite patches (something like Terraform) but this isn't related to how you change image versions.
- alias_neo 4y ago
  I agree with your points, but as I mentioned in another comment, if we take "imperative" and "declarative" as proxy terms for "I do or do not have a reference to the state I requested of the cluster OUTSIDE of the cluster"; my point is that updating the state, in full, by modifying the manifests and committing them to be deployed by your CD pipeline or otherwise is a better approach to ensuring you or someone else can rebuild your "empire" were it to unceremoniously burn to the ground.
  - throwaway894345 4y ago
    I think you’re assuming that just because we’re updating the image via kubectl (which itself is invoked via CD pipeline) that the infrastructure isn’t codified and persisted, which isn’t the case. You can (and should) still have your infrastructure manifests saved in your infra repo/directory and version controlled; that’s orthogonal to how you update the current image version.