Global/Local config infrastructure

[nickolaev]

Summary

To support the Multi-cluster and Hybrid deployments as described in multicluster.md, the Kuma CP binary will be split functionally into a Global CP and Local CP. This issue is to provide the infrastructure, command-line flags, and the appropriate kumactl install mechanisms. No real functionality is envisioned here, rather this will enable project-wide configuration so that the following implementation can leverage the flash to enable/disable particular functionalities in the code.

This is a break down of the work we envision:

• have command line arguments to kuma-cp run. We want three modes --standalone (which is the default if not specified) --local and --global.

• whatever is configured on the command line should be available in the global kuma-cp config as a flag: https://github.com/Kong/kuma/blob/master/pkg/config/app/kuma-cp/config.go#L88

• We need a set of these to verify this works robustly

• We shoudl be able to call kumactl install control-plane --local and it should generate a yaml that invokes the kuma-cp run --local. Essentially it is templetasing this yaml at this place: https://github.com/Kong/kuma/blob/master/app/kumactl/data/install/k8s/control-plane/kuma-cp/app.yaml#L90 and adding something like:

    command: ["kuma-cp"]
    args: {{ .KumaCPArgs }}

The Generate .KumaCPArgs dynamically based on the provided flags.

[nickolaev]

@tharun208 please let me know if you need more information.

[tharun208]

looks fine @nickolaev

[tharun208]

@nickolaev we also need to have a validation if the user tries to run kuma cp run with this own config file which has a different mode of cp rather than the specified one?

[nickolaev]

Yes, and I assume the command line should take preference as it is explicit.
I was also thinking would --mode [standalone|local|global] make more sense than --standalone, --local, --global?

[tharun208]

Yes, and I assume the command line should take preference as it is explicit.
I was also thinking would --mode [standalone|local|global] make more sense than --standalone, --local, --global?

yes, --mode more sense