Added docs for removing compute host

Add docs for removing compute host from an OSA environment.

Change-Id: If203144a25f90c4294b5b78b08d56a6d2a8cf3e9
Closes-Bug: #1588821
Depends-On: I806148974fd0f4b05f6e455a4444e7c70ba05f9a

doc/source/install-guide/ops-removecomputehost.rst

@@ -0,0 +1,52 @@
+`Home <index.html>`_ OpenStack-Ansible Installation Guide
+
+=======================
+Removing a compute host
+=======================
+
+The `openstack-ansible-ops <https://github.com/openstack/openstack-ansible-ops>`_
+repository contains a playbook for removing a compute host from an
+OpenStack-Ansible (OSA) environment.
+To remove a compute host, follow the below procedure.
+
+.. note::
+
+   This guide describes how to remove a compute node from an OSA environment
+   completely. Perform these steps with caution, as the compute node will no
+   longer be in service after the steps have been completed. This guide assumes
+   that all data and instances have been properly migrated.
+
+#. Disable all OpenStack services running on the compute node.
+   This can include, but is not limited to, the ``nova-compute`` service
+   and the neutron agent service.
+
+   .. note::
+
+     Ensure this step is performed first
+
+  .. code-block::
+
+     # Run these commands on the compute node to be removed
+     # stop nova-compute
+     # stop neutron-linuxbridge-agent
+
+#. Clone the ``openstack-ansible-ops`` repository to your deployment host:
+
+  .. code-block::
+
+     $ git clone \
+       https://github.com/openstack/openstack-ansible-ops \
+       /opt/openstack-ansible-ops
+
+#. Run the ``remove_compute_node.yml`` Ansible playbook with the
+   ``node_to_be_removed`` user variable set:
+
+  .. code-block::
+
+     $ cd /opt/openstack-ansible-ops/ansible_tools/playbooks
+     openstack-ansible remove_compute_node.yml \
+     -e node_to_be_removed="<name-of-compute-host>"
+
+#. After the playbook completes, remove the compute node from the
+   OpenStack-Ansible configuration file in
+   ``/etc/openstack_deploy/openstack_user_config.yml``.