Make external load balancer config optional

[pablochacin]

Presently, if multiple control-plane replicas are specified, it is mandatory to specify an external-load-balancer node in the configuration. However, this node configuration can have only one replica and the image parameter is optional, therefore, it would be trivial for the create cluster command to provide the necessary values for launching an external load-balancer if needed.

Forcing to have the external-load-balancer node specification seams more a convenience for maintaining a consistent configuration format (a developer convenience) than a user convenience.

Therefore, it would be convenient for users to have the external load-balancer defined by default if multiple control plane are defined, making the node configuration necessary only if the defaults need to be overridden (e.g. change the image).

[neolit123]

i will have a stab at this today.
/assign
/kind design
/priority important-soon

[BenTheElder]

I'd like to actually remove it from the nodes field too or come up with something more clever because the node keys (eg kubeadm config) are not valid for the load balancer as well.

[neolit123]

but the image field is valid if we want to support a custom LB, i guess?

[pablochacin]

Actually the only reason not to remove the node definition is to been able to specify the load balancer. However, this could be a cluster parameter lile load-balancer-image

[BenTheElder]

I think we should nest it at least like this so we can add other load balancer fields under a subsection if necessary later:

kind: Config
nodes:
  - ...
# optional with defaulting, applies to the control plane LB if one will be provisioned
loadBalancer:
  image:  ...

But you could also imagine more generally setting some control plane details:

kind: Config
nodes:
  - ...
# optional with defaulting, controls control plane details in general
controlPlane:
  # perhaps later we add a field like:
 # address: "127.0.0.1:6443"
 # optional with defaulting, applies to the control plane LB if one will be provisioned
  loadBalancer:
    image:  ...

[pablochacin]

Adding it nested under controlPlane makes sense.

[neolit123]

/unassign
alpha3 will support this.

[BenTheElder]

this is done.