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Most Kubernetes clusters require a
cloud-controller-manager or CSI drivers in order to work properly.
Before introducing the
ControlPlane extension resource Gardener was having several different Helm charts for the
cloud-controller-manager deployments for the various providers.
Now, Gardener commissions an external, provider-specific controller to take over this task.
Which control plane resources are required?
As mentioned in the controlplane customization webhooks document Gardener shall not deploy any
cloud-controller-manager or any other provider-specific component.
Instead, it creates a
ControlPlane CRD that should be picked up by provider extensions.
Its purpose is to trigger the deployment of such provider-specific components in the shoot namespace in the seed cluster.
What needs to be implemented to support a new infrastructure provider?
As part of the shoot flow Gardener will create a special CRD in the seed cluster that needs to be reconciled by an extension controller, for example:
--- apiVersion: extensions.gardener.cloud/v1alpha1 kind: ControlPlane metadata: name: control-plane namespace: shoot--foo--bar spec: type: openstack region: europe-west1 secretRef: name: cloudprovider namespace: shoot--foo--bar providerConfig: apiVersion: openstack.provider.extensions.gardener.cloud/v1alpha1 kind: ControlPlaneConfig loadBalancerProvider: provider zone: eu-1a cloudControllerManager: featureGates: CustomResourceValidation: true infrastructureProviderStatus: apiVersion: openstack.provider.extensions.gardener.cloud/v1alpha1 kind: InfrastructureStatus networks: floatingPool: id: vpc-1234 subnets: - purpose: nodes id: subnetid
.spec.secretRef contains a reference to the provider secret pointing to the account that shall be used for the shoot cluster.
However, the most important section is the
.spec.providerConfig and the
The first one contains an embedded declaration of the provider specific configuration for the control plane (that cannot be known by Gardener itself).
You are responsible for designing how this configuration looks like.
Gardener does not evaluate it but just copies this part from what has been provided by the end-user in the
The second one contains the output of the
Infrastructure resource (that might be relevant for the CCM config).
In order to support a new control plane provider you need to write a controller that watches all
You can take a look at the below referenced example implementation for the Alicloud provider.
The control plane controller as part of the
ControlPlane reconciliation, often deploys resources (e.g. pods/deployments) into the Shoot namespace in the
Seed as part of its
ControlPlane reconciliation loop.
Because the namespace contains network policies that per default deny all ingress and egress traffic,
the pods may need to have proper labels matching to the selectors of the network policies in order to allow the required network traffic.
Otherwise, they won’t be allowed to talk to certain other components (e.g., the kube-apiserver of the shoot).
Please see this document for more information.
Non-provider specific information required for infrastructure creation
Most providers might require further information that is not provider specific but already part of the shoot resource.
One example for this is the GCP control plane controller which needs the Kubernetes version of the shoot cluster (because it already uses the in-tree Kubernetes cloud-controller-manager).
As Gardener cannot know which information is required by providers it simply mirrors the
CloudProfile resources into the seed.
They are part of the
Cluster extension resource and can be used to extract information that is not part of the
Infrastructure resource itself.
References and additional resources
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