Zero footprint installer spec

Change-Id: I4924505f241b0274d270cac39be2feee2ac7d293

specs/stein/zero-footprint-installer.rst

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+..
+ This work is licensed under a Creative Commons Attribution 3.0 Unported
+ License.
+
+ http://creativecommons.org/licenses/by/3.0/legalcode
+
+================================
+TripleO Zero Footprint Installer
+================================
+
+https://blueprints.launchpad.net/tripleo/+spec/zero-footprint
+
+This spec introduces support for an installer mode which has zero
+(or at least much less) dependencies than we do today. It is meant
+to be an iteration of the Undercloud and All-In-One (standalone)
+installers that allows you to end up with the same result without
+having to install all of the TripleO dependencies on your host machine.
+
+Problem Description
+===================
+
+Installing python-tripleoclient on a host machine currently installs
+a lot of dependencies many of which may be optional for smaller
+standalone type installations. Users of smaller standalone installations
+can have a hard time understanding the differences between what TripleO
+dependencies get installed vs which services TripleO installs.
+
+Additionally, some developers would like a fast-track way to develop and
+run playbooks without requiring local installation of an Undercloud which
+in many cases is done inside a virtual machine to encapsulate the dependencies
+that get installed.
+
+Proposed Change
+===============
+
+A new zero footprint installer can help drive OpenStack Tripleoclient
+commands running within a container. Using this approach you can:
+
+1. Generate Ansible playbooks from a set of Heat templates
+   (tripleo-heat-templates), Heat environments, and Heat parameters
+   exactly like we do today using a Container. No local dependencies
+   would be required to generate the playbooks.
+
+2. (optionally) Execute the playbooks locally on the host machine. This would
+   require some Ansible modules to be installed that TripleO depends on but
+   is a much smaller footprint than what we require elsewhere today.
+
+Alternatives
+------------
+
+Create a subpackage of python-tripleoclient which installs less dependencies.
+The general footprint of required packages would still be quite high (lots
+of OpenStack packages will still be installed for the client tooling).
+
+Or do nothing and continue to use VMs to encapsulate the dependencies for
+an Undercloud/All-In-One installer and generate Ansible playbooks. Setting
+up a local VM requires more initial setup and dependencies however and is
+heavier than just using a local container to generate the same playbooks.
+
+Security Impact
+---------------
+
+As a container will be used to generate Ansible playbooks the user may
+need to expose some local data/files to the installer container. This is
+likely a minimal concern as we already require this data to be exposed to
+the Undercloud and All-In-One installers.
+
+Other End User Impact
+---------------------
+
+None
+
+Performance Impact
+------------------
+
+Faster deployment and testing of local All-On-One setups.
+
+Other Deployer Impact
+---------------------
+
+None
+
+
+Developer Impact
+----------------
+
+Faster deployment and testing of local All-On-One setups.
+
+Implementation
+==============
+
+Assignee(s)
+-----------
+
+Primary assignee:
+  dprince
+
+Work Items
+----------
+
+* A new 'tripleoclient' container
+* New project to drive the installation (Talon?)
+* Continue to work on refining the Ansible playbook modules to provide a
+  cleaner set of playbook dependencies. Specifically those that depend on
+  the any of the traditional TripleO/Heat agent hooks and scripts.
+* documentation updates
+
+Dependencies
+============
+
+None.
+
+Testing
+=======
+
+This new installer can likely suppliment or replace some of the testing we
+are doing for All-In-One (standalone) deployments in upstream CI.
+
+Documentation Impact
+====================
+
+Docs will need to be updated.
+
+References
+==========
+
+None