The Cluster controller’s main responsibilities are:
- Setting an OwnerReference on the infrastructure object referenced in
- Setting an OwnerReference on the control plane object referenced in
- Cleanup of all owned objects so that nothing is dangling after deletion.
- Keeping the Cluster’s status in sync with the infrastructureCluster’s status.
- Creating a kubeconfig secret for workload clusters.
The general expectation of an infrastructure provider is to provision the necessary infrastructure components needed to run a Kubernetes cluster. As an example, the AWS infrastructure provider, specifically the AWSCluster reconciler, will provision a VPC, some security groups, an ELB, a bastion instance and some other components all with AWS best practices baked in. Once that infrastructure is provisioned and ready to be used the AWSMachine reconciler takes over and provisions EC2 instances that will become a Kubernetes cluster through some bootstrap mechanism.
The cluster controller will set an OwnerReference on the infrastructureCluster. This controller should normally take no action during reconciliation until it sees the OwnerReference.
An infrastructureCluster controller is expected to eventually have its
spec.controlPlaneEndpoint set by the user/controller.
The Cluster controller bubbles up
status.infrastructureReady from the infrastructureCluster.
The InfrastructureCluster object must have a
spec object must have the following fields defined:
controlPlaneEndpoint- identifies the endpoint used to connect to the target’s cluster apiserver.
status object must have the following fields defined:
ready- a boolean field that is true when the infrastructure is ready to be used.
status object may define several fields that do not affect functionality if missing:
failureReason- is a string that explains why a fatal error has occurred, if possible.
failureMessage- is a string that holds the message contained by the error.
failureDomains- is a
FailureDomainstype indicating the failure domains that machines should be placed in.
FailureDomainsis a map, defined as
map[string]FailureDomainSpec. A unique key must be used for each
FailureDomainSpecis defined as:
controlPlane(bool): indicates if failure domain is appropriate for running control plane instances.
map[string]string): arbitrary attributes for users to apply to a failure domain.
If you are using the kubeadm bootstrap provider you do not have to provide any Cluster API secrets. It will generate all necessary CAs (certificate authorities) for you.
However, if you provide a CA for the cluster then Cluster API will be able to generate a kubeconfig secret. This is useful if you have a custom CA or do not want to use the bootstrap provider’s generated self-signed CA.
|base64 encoded TLS certificate in PEM format
|base64 encoded TLS private key in PEM format
Alternatively can entirely bypass Cluster API generating a kubeconfig entirely if you provide a kubeconfig secret formatted as described below.
|base64 encoded kubeconfig