Project Gardener implements the automated management and operation of Kubernetes clusters as a service. Its main principle is to leverage Kubernetes concepts for all of its tasks.
Recently, most of the vendor specific logic has been developed in-tree. However, the project has grown to a size where it is very hard to extend, maintain, and test. With GEP-1 we have proposed how the architecture can be changed in a way to support external controllers that contain their very own vendor specifics. This way, we can keep Gardener core clean and independent.
Components
Certificate services for Shoot clusters are provided by the composition of two components:
Configuration
Example configuration which is reconciled by this extension controller:
apiVersion: certificate-service.extensions.config.gardener.cloud/v1alpha1
kind: Configuration
metadata:
name: certificate-service
namespace: default
spec:
issuerName: lets-encrypt
namespaceRef: default
resourceNamespace: garden
acme:
email: john.doe@example.com
server: https://acme-v02.api.letsencrypt.org/directory
providers:
clouddns:
- name: clouddns-prod
domains:
- example.io
project: project_id
serviceAccount: |
{
"type": "service_account",
"project_id": "demo-project"
}
route53:
- name: route53-prod
domains:
- example.org
region: us-east-1
accessKeyID: your-accessKeyID
secretAccessKey: your-secretAccessKey
The extension controller will create an instance of Cert-Manager as well as a ClusterIsser with the information provided above.
(Cert-Manager is responsible for managing certificate requests / renewals within the Seed cluster for configured Shoot domains)
Extension-Resources
Besides the configuration, operations also happen on Extension
resources in the extensions.gardener.cloud/v1alpha1
API group of type .spec.type=certificate-service
:
apiVersion: extensions.gardener.cloud/v1alpha1
kind: Extension
metadata:
name: "extension-certificate-service"
namespace: shoot--project--abc
spec:
type: certificate-service
During reconciliation an instance of Cert-Broker is created in the very same namespace the Extension
resource belongs to (Shoot namespace). Cert-Broker relays certificate requests from the Shoot cluster to the Cert-Manager in the Seed and puts back generated certificates. Events are propagated as well.
For security reasons each Shoot cluster must be restricted to only order certificates for domains it owns. The owning domain is extracted from the respective Cluster
resource.
Kubeconfig for Shoot clusters
-
cert-broker: Created with the ca
secret from the Shoot's namespace in the Seed. This Kubeconfig is required by Cert-Broker to watch Ingress
objects, create Secrets
and Events
.
-
gardener: Used to apply RBAC
manifests for Cert-Broker to the Shoot cluster. The gardener
secret is already provided by the Gardener-Controller-Manager
.
Please find more information regarding the extensibility concepts and a detailed proposal here.
How to start using or developing this extension controller locally
You can run the controller locally on your machine by executing make start-certificate-service
.
Please make sure:
$KUBECONFIG
env is set accordingly.
Extension
CRD + Cluster
CRD are applied.
ca
and gardener
secrets for the Shoot cluster exists.
- Configuration is in place.
Static code checks and tests can be executed by running VERIFY=true make all
. We are using dep for Golang package dependency management and Ginkgo/Gomega for testing.
Feedback and Support
Feedback and contributions are always welcome. Please report bugs or suggestions as GitHub issues or join our Slack channel #gardener (please invite yourself to the Kubernetes workspace here).
Learn more!
Please find further resources about out project here: