Developing Cloud Controller Manager [page]deterministic

[definition:cloud-controller-manager]

## 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](https://github.com/kubernetes/cloud-provider/blob/master/cloud.go). 2. Use [`main.go` in cloud-controller-manager](https://github.com/kubernetes/kubernetes/blob/master/cmd/cloud-controller-manager/main.go) 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`](https://github.com/kubernetes/cloud-provider/blob/master/plugins.go).

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 [daemonset](#gloss:daemonset) in your cluster. See [Cloud Controller Manager Administration](/docs/tasks/administer-cluster/running-cloud-controller/) for more details.