specs: rocky: Add new openstack-distribution-packages specification

Add new Rocky specification for installing OpenStack services using the
distribution packages.

Implements blueprint: openstack-distribution-packages
Change-Id: Id5b991c6982609931a7befb1a2a3e74363a3024c

specs/rocky/openstack-distribution-packages.rst

@@ -0,0 +1,133 @@
+Install OpenStack services from distribution packages
+#######################################################
+:date: 2018-03-27 00:00
+:tags: roles, deployment
+
+Blueprint on Launchpad
+
+  * https://blueprints.launchpad.net/openstack-ansible/+spec/openstack-distribution-packages
+
+This spec outlines the work required to enable the OpenStack-Ansible roles to
+install the OpenStack services using the distribution packages from the distribution
+Cloud repositories.
+
+Problem description
+===================
+
+OpenStack-Ansible installs the OpenStack services from the source. Whilst this
+is great in terms of flexibility, it creates some problems such as:
+
+* Long deployment times since wheel packages need to be built and distributed.
+* Unsupported installations by distributions. The versions of OpenStack services
+  built from source do not necessarily match what distributions test together as
+  part of their integration and verification process so it's hard for them to
+  provide support for such installations. As a result of which, operators have
+  limited options when seeking technical support for their deployments.
+
+Proposed change
+===============
+
+Add an additional installation method to all the OpenStack-Ansible roles in
+which the services will be installed using the packages provided by the
+distributions themselves. The default installation method will not change.
+
+Alternatives
+------------
+
+N/A
+
+Playbook/Role impact
+--------------------
+
+All the OpenStack Ansible roles which install OpenStack services (os_*) will be
+impacted by the proposed change. A new variable will be made available on per-role
+basis to allow deployers to select the preferred installation method.
+
+Switching from one installation method to the other will not be supported.
+This can be clarified on the Deployer's documentation and also explicitly detected
+and prevented in the Ansible playbooks possibly by storing a local fact on the host to
+denote the installation method and checking it during upgrades.
+
+Upgrade impact
+--------------
+
+Upgrades should not be impacted since the default installation method will not
+change.
+
+Security impact
+---------------
+
+The security of the overall installation will not change since distributions
+normally backport security fixes which are already present in the upstream packages
+so both installations methods will offer the same level of security reassurances.
+
+Performance impact
+------------------
+
+The overall performance of the deployment will likely be improved since the
+distribution packages normally have their default settings tweaked and
+optimized to match each distribution's environment and needs.
+
+End user impact
+---------------
+
+N/A
+
+Deployer impact
+---------------
+
+The benefit of this new method for deployer's is twofold:
+
+- Use supported packages by distributions and provide feedback back to them.
+  This benefits both distributions and operators since both ends use packages
+  which have passed integration and functional testing before being released.
+- Shorten deployment times since distribution packages are used instead of building
+  new ones from source.
+
+Developer impact
+----------------
+
+N/A
+
+Dependencies
+------------
+
+N/A
+
+Implementation
+==============
+
+Assignee(s)
+-----------
+
+Primary assignee:
+  Markos Chandras (hwoarang)
+
+Work items
+----------
+
+The following work items are the same across all impacted roles
+
+* Move existing installation tasks to a new file (``${role}_install_source.yml``)
+* Create new file (``${role}_install_distro.yml``) with a set of tasks for distribution
+  installations if necessary.
+* Add new variable to allow deployers to select installation method (``${role}_install_method``)
+* Dynamically include the appropriate installation file based on the variable's value
+
+Testing
+=======
+
+Since the default installation method does not change, no new tests are required.
+However, developers may choose to add new jobs on per distribution basis to test
+the new installation method.
+
+Documentation impact
+====================
+
+Documentation needs to be modified to explain how to use the ``distribution``
+installation method.
+
+References
+==========
+
+N/A