Updated subnets field in Machinepool yaml

[shivi28]

What type of PR is this?
/kind bug

What this PR does / why we need it:
Updated doc and template machinepool flavour for subnet field.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #2464

Special notes for your reviewer:

Checklist:

• squashed commits
• includes documentation
• adds unit tests
• adds or updates e2e tests

Release note:

Updated machinepool template and doc for subnet field usage

[randomvariable]

How is this template supposed to work full stop? We need a VPC created and AWSCluster controller to provision subnets before a subnet can be used in the machine pool. Otherwise, you might use BYOI, but this template doesn't support it.

This whole template needs revision and/or the MachinePool controller code needs fixing to work with VPCs provisioned by AWSCluster.

[sedefsavas]

This whole template needs revision and/or the MachinePool controller code needs fixing to work with VPCs provisioned by AWSCluster.

Template doesn't work with the field set, but subnets is an optional field what are we trying to make it work here? When the subnets is nil, it uses AWSCluster subnets.

[sedefsavas]

This whole template needs revision and/or the MachinePool controller code needs fixing to work with VPCs provisioned by AWSCluster.

@randomvariable why do we need to change the code?

[sedefsavas]

Let's follow up on this before the release this week. cc @randomvariable

[sedefsavas]

We can keep this in the docs:
subnets:

• subnet-id

Btw, did you check if this field is working by any chance?

[shivi28]

Yes will receive a validation error. It says invalid type for io.x-k8s.cluster.infrastructure.v1beta1.AWSMachinePool.spec.subnets: got "string", expected "map";

So that's why I removed it from doc as well. Please let me know if you think we should still keep it?

[shivi28]

@sedefsavas I tried multiple use cases in local and found

1. If you have any existing network(VPC and subnet IDs) and want to create AWSMachines in given subnet IDs via AWSMachinePool. Then we have to add existing network in AWSCluster Spec and desired subnet IDs in AWSMachinePool Spec. This will create all AWSMachines in subnets mentioned by AWSMachinePool.spec.subnets
2. But if you want to use default VPC created by AWSCluster and use any existing subnet IDs in AWSMachinePool, then it will throw a ValidationError: One or more security groups in the launch template are not linked to the VPCs configured in the Auto Scaling group.

[sedefsavas]

@shivi28

I confirmed that this works with correct subnet ids that belongs to the VPC cluster is in.

But if you want to use default VPC created by AWSCluster and use any existing subnet IDs in AWSMachinePool, then it will throw a ValidationError: One or more security groups in the launch template are not linked to the VPCs configured in the Auto Scaling group.

[sedefsavas]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: sedefsavas

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [sedefsavas]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment