CCM may not work when Instances or InstancesV2 isn't implemented

[xagent003]

Usecase: We want to use the CCM for LBaaS. We don't have and/or don't want to implement a cloud compute API. The LBaaS functionality just relies on the Service and Node resources.

So kubelet taints the nodes when they come up, until the CCM does it's initialization.

However the CCM expects either Instances or InstancesV2 to be implemented to fetch some metadata. If neither are implemented or the metadata returned is nil, it returns an error here:

cloud-provider/controllers/node/node_controller.go

Line 605 in b60a8ce

return nil, fmt.Errorf("failed to get instances from cloud provider")

syncNode returns prematurely here if metadata is nil or there is an error:

cloud-provider/controllers/node/node_controller.go

Line 434 in b60a8ce

if err != nil {

As a result, it never gets here to remove the taint from the node and update the Node:

cloud-provider/controllers/node/node_controller.go

Line 449 in b60a8ce

n.Spec.Taints = excludeCloudTaint(n.Spec.Taints)

Therefore the node remains tainted and unuseable. But if you look at the code, it seems like the instances metadata can be empty - just not nil. I think syncNode should work if Instances is not implemented - is there any absolute requirement on instances/instance metadata when we want to leverage CCM just for loadbalancers?