website/content/en/docs/tasks/administer-cluster/developing-cloud-controller-manager.md

reviewers	title	content_type	weight
luxas thockin wlan0	Developing Cloud Controller Manager	concept	190

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{{< glossary_definition term_id="cloud-controller-manager" length="all" prepend="The cloud-controller-manager is">}}

Background

Since cloud providers develop and release at a different pace compared to the Kubernetes project, abstracting the provider-specific code to the cloud-controller-manager binary allows cloud vendors to evolve independently from the core Kubernetes code.

The Kubernetes project provides skeleton cloud-controller-manager code with Go interfaces to allow you (or your cloud provider) to plug in your own implementations. This means that a cloud provider can implement a cloud-controller-manager by importing packages from Kubernetes core; each cloudprovider will register their own code by calling cloudprovider.RegisterCloudProvider to update a global variable of available cloud providers.

Developing

Out of tree

To build an out-of-tree cloud-controller-manager for your cloud:

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.

Many cloud providers publish their controller manager code as open source. If you are creating a new cloud-controller-manager from scratch, you could take an existing out-of-tree cloud controller manager as your starting point.

In tree

For in-tree cloud providers, you can run the in-tree cloud controller manager as a {{< glossary_tooltip term_id="daemonset" >}} in your cluster. See Cloud Controller Manager Administration for more details.