openstack : add the external_openstack_lbaas_member_subnet_id variable

[voondo]

What type of PR is this?
/kind feature

What this PR does / why we need it:
It adds the variable external_openstack_lbaas_member_subnet_id which is used to define member-subnet-id in the file roles/kubernetes-apps/external_cloud_controller/openstack/templates/external-openstack-cloud-config.j2

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

Add external_openstack_lbaas_member_subnet_id: str  (not set by default), to define a specific `member-subnet-id` for the openstack load balancers

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: voondo
Once this PR has been reviewed and has the lgtm label, please assign mzaian for approval. For more information see the Code Review Process.

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

Needs approval from an approver in each of these files:

• OWNERS

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

[k8s-ci-robot]

Hi @voondo. Thanks for your PR.

I'm waiting for a kubernetes-sigs member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

I understand the commands that are listed here.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

[yankay]

/ok-to-test

[VannTen]

What happens exactly if the var is not set ? We try to avoid is defined check and have all variables in roles defaults as much as practically possible.

[voondo]

According to the cloud-provider-openstack documentation, it defaults to subnet-id (so external_openstack_lbaas_subnet_id for kubespray) :

member-subnet-id ID of the Neutron network on which to create the members of the load balancer. The load balancer gets another network port on this subnet. Defaults to subnet-id if not set.

https://github.com/kubernetes/cloud-provider-openstack/blob/master/docs/openstack-cloud-controller-manager/using-openstack-cloud-controller-manager.md#load-balancer

Do you think it's better to replicate this behavior in kubespray with something like:

in roles/kubernetes-apps/external_cloud_controller/openstack/defaults/main.yml

external_openstack_lbaas_member_subnet_id: "{{ external_openstack_lbaas_subnet_id }}"

and in roles/kubernetes-apps/external_cloud_controller/openstack/templates/external-openstack-cloud-config.j2

{% if external_openstack_lbaas_subnet_id is defined %}
subnet-id={{ external_openstack_lbaas_subnet_id }}
member-subnet-id={{ external_openstack_lbaas_member_subnet_id }}
{% endif %}

or more directly:

{% if external_openstack_lbaas_subnet_id is defined %}
subnet-id={{ external_openstack_lbaas_subnet_id }}
member-subnet-id={{ external_openstack_lbaas_member_subnet_id | default(external_openstack_lbaas_subnet_id) }}
{% endif %}

?

Note that the template roles/kubernetes-apps/external_cloud_controller/openstack/templates/external-openstack-cloud-config.j2 has already a ton of is defined. Maybe a global refactor would be a good thing but that would be beyond the scope of this pull request.

[VannTen]

Yes, just default to the subnet-it and put it in the same cond block.

Note that the template roles/kubernetes-apps/external_cloud_controller/openstack/templates/external-openstack-cloud-config.j2 has already a ton of is defined. Maybe a global refactor would be a good thing but that would be beyond the scope of this pull request.

Yes to both (and not just this file, the idiom is plaguing kubespray everywhere and that makes templates significantly harder to read ^^)