k8s_api - a CoreDNS plugin that enables other plugins to register/share Kubernetes API watches.

k8s_api enables any plugin that implements the k8sapi.APIWatcher interface to register Kubernetes API informers and share access to object stores.

type APIWatcher interface {

	// Informers should return a list of functions that return an Kubernetes Object Informer, each mapped by watch name.
	// k8s_api will start each Informer on the API connection. If multiple plugins return an Informer func with the same
	// name, the first plugin (per plugin execution order), will take precedence.
	Informers() map[string]InformerFunc

	// SetIndexer should set the index passed to a local pointer to be used by the plugin.  k8s_api calls this function
	// for *all* Informers added via the Informers() function by any plugins implementing APIWatcher. This enables
	// multiple plugins to share the same store/index managed by a single Informer.
	SetIndexer(string, cache.KeyListerGetter) error

	// SetHasSynced should set the HasSyncedFunc passed to a local function to be used by the plugin. Implement this
	// if the plugin needs to know if the API informers have fully synced (i.e. completed initial list action before
	// beginning the watch).
	SetHasSynced(HasSyncedFunc)
}

k8s_api {
    endpoint URL
    tls CERT KEY CACERT
    kubeconfig KUBECONFIG CONTEXT
}

• endpoint specifies the URL for a remote k8s API endpoint. If omitted, it will connect to k8s in-cluster using the cluster service account.
• tls CERT KEY CACERT are the TLS cert, key and the CA cert file names for remote k8s connection. This option is ignored if connecting in-cluster (i.e. endpoint is not specified).
• kubeconfig KUBECONFIG CONTEXT authenticates the connection to a remote k8s cluster using a kubeconfig file. It supports TLS, username and password, or token-based authentication. This option is ignored if connecting in-cluster (i.e., the endpoint is not specified).

k8s_api is an external plugin, which means it is not included in CoreDNS releases. To use k8s_api, you'll need to build a CoreDNS image with k8s_api. In a nutshell you'll need to:

• Clone https://github.com/coredns/coredns into $GOPATH/src/github.com/coredns
• Add this plugin to plugin.cfg per instructions therein. This plugin must be ordered after any plugins that use it (i.e. plugins that implement APIWatcher).
• make -f Makefile.release DOCKER=your-docker-repo release
• make -f Makefile.release DOCKER=your-docker-repo docker
• make -f Makefile.release DOCKER=your-docker-repo docker-push

Example plugins that implement k8sapi.APIWatcher can be found in the examples directory.