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Developing Cloud Controller Manager

FEATURE STATE: Kubernetes v1.11 beta
This feature is currently in a beta state, meaning:

  • The version names contain beta (e.g. v2beta3).
  • Code is well tested. Enabling the feature is considered safe. Enabled by default.
  • Support for the overall feature will not be dropped, though details may change.
  • The schema and/or semantics of objects may change in incompatible ways in a subsequent beta or stable release. When this happens, we will provide instructions for migrating to the next version. This may require deleting, editing, and re-creating API objects. The editing process may require some thought. This may require downtime for applications that rely on the feature.
  • Recommended for only non-business-critical uses because of potential for incompatible changes in subsequent releases. If you have multiple clusters that can be upgraded independently, you may be able to relax this restriction.
  • Please do try our beta features and give feedback on them! After they exit beta, it may not be practical for us to make more changes.

In upcoming releases, Cloud Controller Manager will be the preferred way to integrate Kubernetes with any cloud. This will ensure cloud providers can develop their features independently from the core Kubernetes release cycles.

FEATURE STATE: Kubernetes 1.8 alpha
This feature is currently in a alpha state, meaning:

  • The version names contain alpha (e.g. v1alpha1).
  • Might be buggy. Enabling the feature may expose bugs. Disabled by default.
  • Support for feature may be dropped at any time without notice.
  • The API may change in incompatible ways in a later software release without notice.
  • Recommended for use only in short-lived testing clusters, due to increased risk of bugs and lack of long-term support.

Before going into how to build your own cloud controller manager, some background on how it works under the hood is helpful. The cloud controller manager is code from kube-controller-manager utilizing Go interfaces to allow implementations from any cloud to be plugged in. Most of the scaffolding and generic controller implementations will be in core, but it will always exec out to the cloud interfaces it is provided, so long as the cloud provider interface is satisfied.

To dive a little deeper into implementation details, all cloud controller managers will import packages from Kubernetes core, the only difference being each project will register their own cloud providers by calling cloudprovider.RegisterCloudProvider where a global variable of available cloud providers is updated.

Developing

Out of Tree

To build an out-of-tree cloud-controller-manager for your cloud, follow these steps:

  1. Create a go package with an implementation that satisfies cloudprovider.Interface.
  2. Use main.go in cloud-controller-manager from Kubernetes core as a template for your main.go. As mentioned above, the only difference should be the cloud package that will be imported.
  3. Import your cloud package in main.go, ensure your package has an init block to run cloudprovider.RegisterCloudProvider.

Using existing out-of-tree cloud providers as an example may be helpful. You can find the list here.

In Tree

For in-tree cloud providers, you can run the in-tree cloud controller manager as a Daemonset in your cluster. See the running cloud controller manager docs for more details.

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