Support disabling OpenStack Loadbalancer integration

[Nikolay Vinogradov]

Hi all,

 Sometimes it might be useful to support alternative LB implementations when running Charmed Kubernetes on Openstack, such as MetalLB for example, or others. Openstack Cloud Controller Manager provides not only the load balancer integration, but also Cinder volume integration, so it is not easy to completely avoid deploying it on top of Charmed Kubernetes on Openstack. Then, if we wanted to use MetalLB (say in L2 mode) as the load balancer instead of Octavia and Cinder volume integration from openstack-integrator charm, we would deploy MetalLB operator next to openstack-integrator. However, by default, if we expose a Kubernetes service with LoadBalancer type, then both Openstack Cloud Controller Manager (C-C-M) and MetalLB attempt to create a load balancer for the service and only one of them will be actually providing the external IP for the service.

 To prevent that, it would be good if openstack-integrator charm allowed to disable Loadbalancer integration as described in [1]: by exposing 'enabled-lb' option that is propagated to the cloud.conf secret used by the C-C-M.

 It is worth mentioning here that MetalLB charm can also be improved to support filtering by loadBalancerClass [2], as per [3].

 [1] https://github.com/kubernetes/cloud-provider-openstack/blob/master/docs/openstack-cloud-controller-manager/using-openstack-cloud-controller-manager.md#load-balancer
 [2] https://kubernetes.io/docs/concepts/services-networking/service/#load-balancer-class
 [3] https://bugs.launchpad.net/operator-metallb/+bug/1994064/comments/1

[Nikolay Vinogradov (nikolay.vinogradov)]

Please see the initial set of patches below, the work is currently in progress.

- https://github.com/juju-solutions/interface-openstack-integration/compare/master...nikolayvinogradov:interface-openstack-integration:loadbalancer-enabled
- https://github.com/charmed-kubernetes/layer-kubernetes-common/compare/main...nikolayvinogradov:layer-kubernetes-common:loadbalancer-enabled
- https://github.com/juju-solutions/charm-openstack-integrator/compare/master...nikolayvinogradov:charm-openstack-integrator:loadbalancer-enabled

[George Kraft (cynerva)]

PRs:
https://github.com/juju-solutions/interface-openstack-integration/pull/13
https://github.com/juju-solutions/charm-openstack-integrator/pull/67
https://github.com/charmed-kubernetes/layer-kubernetes-common/pull/40
https://github.com/canonical/openstack-cloud-controller-operator/pull/3

[Nikolay Vinogradov (nikolay.vinogradov)]

Probably it is worth mentioning here that the feature is available in the Openstack Cloud Controller Manager image since version 1.24 and newer.

See https://github.com/kubernetes/cloud-provider-openstack/pull/1777/files for more information.