Why does the server not have a resource type called istiod?

The reason why a server doesn't have a resource type specifically called "istiod" is rooted in how Istio, the service mesh, is architected and how Kubernetes resources are defined.

Here's a breakdown:

1. Istiod as a Control Plane Component:

- `istiod` is the central control plane component of Istio. It is responsible for configuring and managing the Istio service mesh. It's not a resource in the same way that a Kubernetes Deployment or Service is.

2. Kubernetes Custom Resource Definitions (CRDs):

- Istio extends Kubernetes through Custom Resource Definitions (CRDs). These CRDs define custom resources like `VirtualService`, `DestinationRule`, `Gateway`, etc. These resources are used to configure Istio's behavior within the mesh. `istiod` is the component that acts upon these resources.

3. `istiod` Deployment:

- `istiod` itself is usually deployed as a Kubernetes Deployment, often named `istiod`. It is not treated as a resource that you would configure using a CRD; instead, its configuration is done through its deployment settings and the environment variables.

4. Why not a CRD?:

- Creating a CRD for `istiod` would be counterproductive. The CRDs are meant for the user to configure the application behavior and the mesh, not the control plane. The settings of `istiod` are not intended to be changed very frequently. Instead, configuration of the behavior within the mesh is done by manipulating other CRDs like VirtualServices etc.

5. Configuration:

- `istiod` is typically configured through its deployment YAML or Helm values. This configuration includes settings like resource limits, replicas, and other control plane specific configurations. It's not intended to be modified through Istio's CRDs.

6. Analogy:

- Think of it like this: Kubernetes provides the "operating system" and CRDs are like applications or configurations you install on top of it. `istiod` is part of the "system" (or the control plane), not a configurable application on top of Kubernetes in the way that an individual service configured by a `VirtualService` would be.

In summary, `istiod` is a core control plane component that acts on Istio's CRDs, not a resource itself. It is usually deployed as a standard Kubernetes Deployment and configured through its deployment settings. The focus is on configuring the behavior of the mesh through resources defined by CRDs, not configuring the `istiod` process as a resource.

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