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.

Example configuration for this extension controller:

apiVersion: shoot-cert-service.extensions.config.gardener.cloud/v1alpha1
kind: Configuration
issuerName: gardener
restrictIssuer: true # restrict issuer to any sub-domain of shoot.spec.dns.domain (default)
acme:
  email: [email protected]
  server: https://acme-v02.api.letsencrypt.org/directory
# privateKey: | # Optional key for Let's Encrypt account.
#   -----BEGIN BEGIN RSA PRIVATE KEY-----
#   ...
#   -----END RSA PRIVATE KEY-----

Example extension resource:

apiVersion: extensions.gardener.cloud/v1alpha1
kind: Extension
metadata:
  name: "extension-certificate-service"
  namespace: shoot--project--abc
spec:
  type: shoot-cert-service

When an extension resource is reconciled, the extension controller will create an instance of Cert-Management as well as an Issuer with the ACME information provided in the configuration above. These resources are placed inside the shoot namespace on the seed. Also, the controller takes care about generating necessary RBAC resources for the seed as well as for the shoot.

Please note, this extension controller relies on the Gardener-Resource-Manager to deploy k8s resources to seed and shoot clusters, i.e. it never deploys them directly.

You can run the controller locally on your machine by executing make start. Please make sure to have the kubeconfig to the cluster you want to connect to ready in the ./dev/kubeconfig file. Static code checks and tests can be executed by running VERIFY=true make all. We are using Go modules for Golang package dependency management and Ginkgo/Gomega for testing.

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).

Please find further resources about out project here:

• Our landing page gardener.cloud
• "Gardener, the Kubernetes Botanist" blog on kubernetes.io
• "Gardener Project Update" blog on kubernetes.io
• Gardener Extensions Golang library
• GEP-1 (Gardener Enhancement Proposal) on extensibility
• Extensibility API documentation