Add missing CloudKitty documentation.

* Fix various typos and formatting.
* Add documentation about custom collector backend.
* Add documentation about custom storage backend.

Change-Id: If937afc5ce2a2747f464fbaf38a5dcf2e57ba04f
Closes-bug: #1940842

doc/source/conf.py

@@ -90,6 +90,7 @@ openstackdocs_bug_tag = ''
 openstack_projects = [
     'bifrost',
     'cinder',
+    'cloudkitty',
     'designate',
     'glance',
     'ironic',

doc/source/reference/index.rst

@@ -18,3 +18,4 @@ Projects Deployment Configuration Reference
    deployment-config/index
    deployment-and-bootstrapping/index
    high-availability/index
+   rating/index

doc/source/reference/rating/cloudkitty-guide.rst

@@ -0,0 +1,70 @@
+.. _cloudkitty-guide:
+
+=================================
+CloudKitty - Rating service guide
+=================================
+
+Overview
+~~~~~~~~
+CloudKitty is the Openstack service used to rate your platform usage.
+As a rating service, CloudKitty does not provide billing services such as
+generating a bill to send to your customers every month.
+
+However, it provides you the building bricks you can use to build your own
+billing service upon internally.
+
+Because cloudkitty is a flexible rating service, it's highly customizable while
+still offering a generic approach to the rating of your platform.
+
+It lets you choose which metrics you want to rate, from which datasource
+and where to finally store the processed rate of those resources.
+
+This document will explain how to use the different features available and that
+Kolla Ansible supports.
+
+See the :cloudkitty-doc:`CloudKitty documentation </>` for further information.
+
+CloudKitty Collector backend
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+CloudKitty natively supports multiple collector backends.
+
+By default Kolla Ansible uses the Gnocchi backend,
+however we also support using the following backend types:
+
+- ``prometheus`` - Use Prometheus metrics as dataset for cloudkitty to process.
+- ``monasca`` - Use Openstack Monasca metrics as dataset for cloudkitty to
+  process.
+
+The configuration parameter related to this option is
+``cloudkitty_collector_backend``.
+
+To use the Prometheus collector backend:
+
+.. code-block:: yaml
+
+   cloudkitty_collector_backend: prometheus
+
+Alternatively, to use the Monasca collector backend:
+
+.. code-block:: yaml
+
+   cloudkitty_collector_backend: monasca
+
+Cloudkitty Storage Backend
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+As for collectors, CloudKitty supports multiple backend to store ratings.
+By default, Kolla Ansible uses the InfluxDB based backend.
+
+Another famous alternative is Elasticsearch and can be activated in Kolla
+Ansible using the ``cloudkitty_storage_backend``  configuration option in
+your ``globals.yml`` configuration file:
+
+.. code-block:: yaml
+
+   cloudkitty_storage_backend: elasticsearch
+
+You can only use one backend type at a time, selecting elasticsearch
+will automatically enable Elasticsearch deployment and creation of the
+required CloudKitty index.

doc/source/reference/rating/index.rst

@@ -0,0 +1,11 @@
+=======
+Rating
+=======
+
+This section describes configuring rating service
+such as CloudKitty.
+
+.. toctree::
+   :maxdepth: 1
+
+   cloudkitty-guide