Open Stack

Hey all,

Over the past few months, there's been a lot of discussion and work around
creating a new REST API-supported TripleO deployment workflow.  However most
of that discussion has been fragmented within spec reviews and weekly IRC
meetings, so I thought it might make sense to provide a high-level overview
of what's been going on.  Hopefully it'll provide some useful perspective for
those that are curious!

Thanks,
Tzu-Mainn Chen

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1. Explanation for Deployment Workflow Change

TripleO uses Heat to deploy clouds.  Heat allows tremendous flexibility at the
cost of enormous complexity.  Fortunately TripleO has the space to allow
developers to create tools to simplify the process tremendously,  resulting in
a deployment process that is both simple and flexible to user needs.

The current CLI-based TripleO workflow asks the deployer to modify a base set
of Heat environment files directly before calling Heat's stack-create command.
This requires much knowledge and precision, and is a process prone to error.

However this process can be eased by understanding that there is a pattern to
these modifications; for example, if a deployer wishes to enable network
isolation, a specific set of modifications must be made.  These  modification
sets can be encapsulated through pre-created Heat environment files, and TripleO
contains a library of these
(https://github.com/openstack/tripleo-heat-templates/tree/master/environments).

These environments are further categorized through the proposed environment
capabilities map (https://review.openstack.org/#/c/242439).  This mapping file
contains programmatic metadata, adding items such as user-friendly text around
environment files and marking certain environments as mutually exclusive.


2. Summary of Updated Deployment Workflow

Here's a summary of the updated TripleO deployment workflow.

    1. Create a Plan: Upload a base set of heat templates and environment files
       into a Swift container.  This Swift container will be versioned to allow
       for future work with respect to updates and upgrades.

    2. Environment Selection: Select the appropriate environment files for your
       deployment.

    3. Modify Parameters: Modify additional deployment parameters.  These
       parameters are influenced by the environment selection in step 2.

    4. Deploy: Send the contents of the plan's Swift container to Heat for
       deployment.

Note that the current CLI-based workflow still fits here: a deployer can modify
Heat files directly prior to step 1, follow step 1, and then skip directly to
step 4.  This also allows for trial deployments with test configurations.


3. TripleO Python Library, REST API, and GUI

Right now, much of the existing TripleO deployment logic lives within the TripleO
CLI code, making it inaccessible to non-Python based UIs.   Putting both old and
new deployment logic into tripleo-common and then creating a REST API on top of
that logic will enable modern Javascript-based GUIs to create cloud deployments
using TripleO.


4. Future Work - Validations

A possible next step is to add validations to the TripleO toolkit: scripts that
can be used to check the validity of your deployment pre-, in-, and  post-flight.
These validations will be runnable and queryable through a  REST API.  Note that
the above deployment workflow should not be a requirement for validations to be
run.


5. In-Progress Development

The initial spec for the tripleo-common library has already been approved, and
various people have been pushing work forward.  Here's a summary:

* Move shared business logic out of CLI
  * https://review.openstack.org/249134 - simple validations (WIP)
  * https://review.openstack.org/228991 - deployment code (ready for review)

* Additional TripleO business logic
  * rename tripleo-common repo to tripleo
    * https://review.openstack.org/#/c/249521/ (ready for review)
    * https://review.openstack.org/#/c/249524/ (ready for review)
    * https://review.openstack.org/#/c/247834/ (ready for review)
  * https://review.openstack.org/#/c/242439 - capabilities map (ready for review)
  * https://review.openstack.org/#/c/227297/ - base tripleo library code (ready for review)
  * https://review.openstack.org/#/c/232534/ - utility functions to manage environments (ready for review)
  * after the above is merged, plan.py will need to be updated to include environment methods

* TripleO API
  * https://review.openstack.org/#/c/230432/ - API spec (ready for review)
  * https://review.openstack.org/#/c/243737/  - API (WIP)
  * after the library code is fully merged, API will need to be updated to allow access
    to a plan's environment manipulation methods