K8s datasource configuration doc

this document describes how to config kubernetes datasource:

   * copy kubernetes cluster config file
   * copy keys to establish SSL connection
   * config vitrage.conf

Change-Id: I146cf9811cedffb2e4fed6ee96937e6c53e44588

doc/source/contributor/configuration.rst

@@ -25,7 +25,7 @@ Datasources
    static-config
    static-physical-config
    zabbix_vitrage
-
+   k8s_datasource
 
 Notifiers
 ---------

doc/source/contributor/k8s_datasource.rst

@@ -0,0 +1,83 @@
+=====================
+Kubernetes datasource
+=====================
+
+This document describes how to configure kubernetes datasource properly.
+Note that currently we support only Kubernetes on top of Nova (k8s nodes must be nova.instance)
+
+Datasource configuration
+------------------------
+
+
+Step 1
+_______
+
+In order to access k8s cluster the following files should be copied from k8s master and stored in the same machine as vitrage :
+  * kubeconfig - kubernetes cluster config file is called kubeconfig.
+  * certificate-authority (ca.pem)
+  * client-certificate (kubectl.pem)
+  * client-key (kubectl-key.pem)
+
+
+
+Kubeconfig example  ::
+
+
+	apiVersion: v1
+	kind: Config
+	clusters:
+	- cluster:
+		certificate-authority: /home/k8s/ca.pem
+		server: https://<IP>:<Port>
+	  name: bcmt-kubernetes
+	contexts:
+	- context:
+		cluster: bcmt-kubernetes
+		namespace: kube-system
+		user: kubelet
+	  name: kubelet-context
+	current-context: kubelet-context
+	preferences: {}
+	users:
+	- name: kubelet
+	  user:
+		client-certificate: /home/k8s/kubectl.pem
+		client-key: /home/k8s/kubectl-key.pem
+
+
+
+keys location (.pem) is usually at ``/etc/kubernetes/ssl``
+
+kubeconfig is usually at ``$HOME/.kube/config``
+
+Make sure to place the files in the same path as written in kubeconfig file.
+for example ``ca.pem`` at ``/home/k8s/ca.pem``
+
+
+
+Better option is to create a new user + corresponding SSL keys
+
+This requires new SSL keys and some basic understanding in kubernetes (config new user credentials and rules).
+this might be more complicated than the first approach.
+
+
+Step 2
+_______
+
+In ``/etc/vitrage/vitrage.conf``:
+
+Set the location for kubeconfig file:
+
+[kubernetes]
+
+config_file = /home/k8s/kubeconfig
+
+
+Add kubernetes to the list of active datasources:
+
+[datasources]
+
+types = nova.host,nova.instance,nova.zone,aodh,static,cinder.volume,neutron.network,neutron.port,kubernetes
+
+
+