AWSManagedMachinePool - Launch Template support

[michaelbeaumont]

/kind feature

Describe the solution you'd like
The managed EKS nodegroups backing AWSManagedMachinePool support launch templates. This functionality was put on hold until both the AWSMachinePools and AWSManagedMachinePools support was merged.

Anything else you would like to add:
Discussed in #1916 (comment)

[michaelbeaumont]

/assign
/lifecycle active

[michaelbeaumont]

@richardcase @felipeweb Right now, AWSMachinePool supports setting a limited number of options for launch templates inline with the resource, most of which are covered by the Nodegroup API in the AWSManagedMachinePool case. I think it would make the most sense to only support referencing a launch template by ID with AWSManagedMachinePool. WDYT?

[felipeweb]

IMHO we need to be able to add the extra kubelet args passed in the EKSConfig object in the Launch template even if an Launch template ID is not passed to the mamagedmachinepool. The node-labels argument must to be added here too

cluster-api-provider-aws/pkg/cloud/services/eks/nodegroup.go

Line 168 in b7294ce

Labels: aws.StringMap(managedPool.Labels),

and other fields we need to pass inside userdata because nodegroup creation does not support passing those fields as parameter. here is an example how eksctl does this

https://github.com/weaveworks/eksctl/blob/9688e7fe82eccc6ea7cdc6bca80891cb8acf2d92/pkg/cfn/builder/managed_launch_template.go#L178

[michaelbeaumont]

It's slightly more complicated I think, eksctl doesn't allow you to pass arbitrary kubelet args to a managed nodegroup.
The user data for managed nodegroups must follow the guidelines laid out in the docs which prevent the userdata from calling the bootstrap directly, I believe, because the user data is merged unless using a custom AMI (EDIT: i.e. specifying an AMI, which is what we do now with AWSMachinePool using the recommended EKS optimized AMI, as opposed to letting EKS pick the image).

I think we'll need to switch to always using launch templates and always specify an AMI in the launch template.

[randomvariable]

@richardcase up to you where you want to do this.
I think one of us, me, @JoelSpeed or you were going to diff options with AWSMachine.

[richardcase]

Yeah we need to do the diff and come up with a solution that i think we should document via an ADR. I'm happy to do this diff before the next office hours.