Support Minimal Control Plane install

[Pothulapati]

linkerd/linkerd2#4612

This RFC aims to get high level information, suggestions, questions, feedback on the minimal control-plane installation, so that the implementation can be drafted accordingly.

Summary

An incremental approach to installing Linkerd, with support for additional dependencies.

Problem Statement (Step 1)

Linkerd's control plane components can work independently(example: Tap, etc)
but currently, the installation logic is tightly coupled i.e in a single chart
(except for prometheus and grafana). This has the following problems:

• Components can't be skipped during installation.
• No incremental way of installing components as required.

Once the proposal is implemented, Users will be able to

• Use the Linkerd CLI or Helm to install a minimal control plane with only the
  bare essentials of functionality.
• Use the Linkerd CLI or Helm to install addon charts such as Linkerd-viz to add
  functionality to the minimal control plane independently.
• Use linkerd install or full control-plane to install a complete Linkerd control
  plane including full observability, just like they can today.

Goals

• Remove tight coupling between control-plane components with installation.
• Provide an incremental installation approach of the control-plane along with a
  upgrade story.
• Update Dashboards and CLI to work as per the installed components.

Rendered

cc: @grampelberg

Signed-off-by: Tarun Pothulapati tarunpothulapati@outlook.com

[olix0r]

This was accidentally closed when we changed the default branch to main. The base should probably be updated...