Terminology woes

[jannfis]

Seeking input on the following:

Terminology becomes increasingly difficult to understand. We use the words "control plane", "hub", "principal", "workload cluster", "spoke" and "agent" or "agent system" interchangeable throughout everywhere.

While I think it's clear we should refer to "principal" and "agent" exclusively when referring to the appropriate components of argocd-agent, what do people think how we should refer to the systems?

Is "hub" and "spoke"/"spokes" the better, more understandable terminology?

Or is "control plane" and "data plane" (or, as we right now frame them, "workload clusters") the more understandable one?

Are there other terms that might better reflect the agent's architecture and components?

[christianh814]

There is a precedence by Istio that was set to call it "control plane" and "data plane" FWIW

[mikeshng]

kubernetes/community#8210

For multicluster, PTAL at this PR as well. We are trying to standardize a terminology for the "hub cluster".

[gnunn1]

I prefer "hub cluster" and "managed cluster" for the hub and spokes respectively, personally I don't like the term "data plane" at all.

The sig-multicluster Work API seems to use the hub and managed cluster terms as well as a data point.

https://multicluster.sigs.k8s.io/concepts/work-api/#terminology

[christianh814]

@gnunn1 Surprise surprise, but I disagree 😂

For me "hub and spoke" describes Argo CD as it is now. Central Hub that manages the Spokes. This isn't what's happening with Argo CD Agent.

Not a fan of "data plane" as well, but it's more accurate to what's happening.

For me it's either "Control Plane/Data Plane" or "Principal and Agent". But I don't see this design as a "hub and spoke"

[jannfis]

I have some concerns around the term of "managed cluster" in this very context - argocd-agent does not manage the cluster nor really any workloads on it, it really does only sync Argo CD configuration back and forth.

[gnunn1]

I can understand where you are coming from but from my PoVbif embracing it is being managed by Argo CD for configuration and apps? Are you worried it overstates for scenarios where Argo CD is only deploying a handful of apps versus doing it all?

Maybe "Client Cluster" or "Target Cluster" are better choices?

[jannfis]

To me, when I hear the term "managed cluster", I think somebody/something manages the cluster, including the lifecycle of the cluster itself.

In the case of e.g. Open Cluster Management, I agree that the term makes sense because in fact, those clusters - not only the workloads running on it - are centrally managed.

Therefore, I think for argocd-agent, using the term "managed" is a bit confusing and potentially misleading. But that is just my perception, happy to hear other opinions.

[jannfis]

For me it's either "Control Plane/Data Plane" or "Principal and Agent". But I don't see this design as a "hub and spoke"

For the case of data plane, how are the individual systems in the data plane called? Are they "data plane clusters", similar to the "control plane cluster"?

[illrill]

Azure calls it "hub cluster" and "member cluster" in their similar product: https://learn.microsoft.com/en-us/azure/kubernetes-fleet/concepts-fleet