Reference to "config-only" deployments in "Best Practices"

[davidmichaelkarr]

Our large K8s-based enterprise currently does automated deployments in a custom way, with scripting to manage the process. We're now looking at using Argo Rollouts to better automate that process. I've been going through the docs in the last couple of days so I know what to expect.

As we currently use Deployment objects, we're considering defining the Rollout object with a workloadRef pointing to the original Deployment object.

Besides our full "deployment" jobs, we also have what I would call "config-only" deployments, where the configmap associated with the service is changed, and we just restart the pods. In the "Best Practices" section, there is an entry titled "Rollout a ConfigMap change". The info in this topic seems wrong, as it says this:

"Each time a change occurs in the ConfigMap, its name will change in the Deployment reference as well, triggering a Rollout."

This seems to imply that the rollouts controller not only watches for changes in the Rollout object, but the Deployment object referred to in a workloadRef, but I was under the impression that it does not do that. I have a feeling something else was intended to be stated here.

[kostis-codefresh]

Hello

The documentation is written confusingly, but it assumes you are using a Rollout resource.

When it talks about "deployment reference" it means the reference of the configmap inside the Deployment/Rollout itself and not the "workloadRef" field you are thinking about.

This seems to imply that the rollouts controller not only watches for changes in the Rollout object, but the Deployment object referred to in a workloadRef, but I was under the impression that it does not do that.

Actually I would have expected Argo Rollouts to monitor both the Rollout and the Deployment. At the very least it should monitor the container image in the linked Deployment in order to understand when a new image update must happen. Did you try this in your environment and it didn't work?

[davidmichaelkarr]

I haven't tried anything at all yet. I'm only consuming documentation at this point. I don't yet have a cluster with the rollouts controller installed.

[kostis-codefresh]

You might find this guide of mine very interesting https://codefresh.io/blog/progressive-delivery-for-kubernetes-config-maps-using-argo-rollouts/

I never tested this with workloadref but I suspect it will work the same way.

[kostis-codefresh]

Here is the repo if you want to test the same scenario yourself. You could also edit it to use workloadref and see how it behaves https://github.com/kostis-codefresh/configmaps-argo-rollouts-example/tree/main