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.

This controller operates on the OperatingSystemConfig resource in the extensions.gardener.cloud/v1alpha1 API group. It manages those objects that are requesting CoreOS container linux (Alicloud) configuration (.spec.type=coreos-Alicloud):

---
apiVersion: extensions.gardener.cloud/v1alpha1
kind: OperatingSystemConfig
metadata:
  name: pool-01-original
  namespace: default
spec:
  type: coreos-alicloud
  units:
    ...
  files:
    ...

Please find a concrete example in the example folder.

After reconciliation the resulting data will be stored in a secret within the same namespace (as the config itself might contain confidential data). The name of the secret will be written into the resource's .status field:

...
status:
  ...
  cloudConfig:
    secretRef:
      name: osc-result-pool-01-original
      namespace: default
  command: /usr/bin/env bash <path>
  units:
  - docker-monitor.service
  - kubelet-monitor.service
  - kubelet.service

The secret has one data key cloud_config that stores the generation.

An example for a ControllerRegistration resource that can be used to register this controller to Gardener can be found here.

Please find more information regarding the extensibility concepts and a detailed proposal here.

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 make verify. 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