Overview for the design of tripleo-quickstart

Overview for the design of tripleo-quickstart

One of the barriers to entry for trying out TripleO and its derivatives has been the relative difficulty in getting an environment up quickly and understanding the steps required. The TripleO team has solved these two fundamental problems with tripleo-quickstart. This document will serve as a place to document the high level design of tripleo-quickstart and how the design solves users problems.

What is tripleo-quickstart?

When we refer to tripleo-quickstart we often are talking about two separate projects tripleo-quickstart and tripleo-quickstart-extras. The following is a brief description of each project.

  • tripleo-quickstart is an Ansible tool that provisions the virtual guests, networking, and other environmental details to enable a kvm guest based deployment of TripleO. This is very handy for development, test, or proof of concept (POC) deployments.
  • tripleo-quickstart-extras are a set of composable Ansible roles that can be used to configure, deploy, perform post install actions like scale or upgrade TripleO. These individual Ansible roles are narrow in scope to do one thing and one thing well. The tightly scoped roles also allows smart parts of the project to be easily overridden when required. These roles are designed to be self documenting and match the official TripleO documentation.

Problems tripleo-quickstart attempts to solve

  • Automate the setup and deployment of TripleO
  • Make the deployment as fast as possible
  • Help make the TripleO deployment easier to understand and welcoming to newcomers
  • Make a tool that is attractive to OpenStack developers

Scenarios

  1. Jake the OpenStack developer has a test computer, he has installed OpenStack with DevStack but is interested in TripleO. Jake has some experience with OpenStack but could be considered a relative newcomer.
  2. Joan is an experienced OpenStack developer that is looking to develop and test her patches to OpenStack in various ways and testing environments.

Platform support

  • CentOS
  • Red Hat Enterprise Linux
  • Fedora [*]

TripleO-Quickstart deploys TripleO therefore is also subject to TripleO’s requirements.

Problem: Automate the setup and deployment of TripleO

There are many tools one can use to automated the deployment of TripleO, we have chosen Ansible. The following is a list of design decisions made to solve the problem.

  • Use ansible to provision a libvirt environment in which to deploy OpenStack with TripleO
  • Use ansible’s composable roles and playbooks to provide a flexible and repeatable experience.
Solve for Scenario #1
  • Focus on virtualization tools available in CentOS and Red Hat Enterprise Linux, use libvirt

  • Create a easy to use script to execute tripleo-quickstart e.g. quickstart.sh that Jake can just download and execute

    Example::

    curl -O https://raw.githubusercontent.com/openstack/tripleo-quickstart/master/quickstart.sh
    bash quickstart.sh <host>
    
Solve for Scenario #2

Problem: Make the deployment as fast as possible

A deployment of TripleO by default takes more time to install than let’s say DevStack. TripleO is a much more robust and capable deployment so with great power comes great patience. People are not always patient so how can we speed up the deployment? By building preinstalled images we hope to improve the install time of TripleO.

  • We have created the build image ansible role.
  • The TripleO team hosts TripleO images for the public at ci.centos and here

Problem: Help make the deployment steps easier to understand

Deploying any OpenStack distribution and understanding what is happening behind the scenes is not easy for newcomers. Ideally we would have a tool that prints out the documentation and executes each step for the user. This way one would have the commands required for a deployment and the context to give each command meaning.

Solve for Scenario #1
  • Provision an environment and create all the scripts and documentation one needs for a successful deployment without automatically deploying. Let the user take it step by step while reading and analyzing the commands with the in-line documentation.
Solve for Scenario #2

We could translate the deployment steps into ansible and use OpenStack libraries built for OpenStack like shade Both tools are very well designed and would be more than sufficient to deploy OpenStack with TripleO. We would be afforded idempotency and other benefits of ansible, why not use these tools?

Answer for Scenario #1
  • It’s important that users can directly map official TripleO documentation to the steps automated in this tool. The official TripleO and Red Hat OpenStack Platform both document the deployment using bash commands. New users may not be able to translate ansible to bash and vice versa.
Answer for Scenario #2
  • Not every OpenStack developer is experienced with Ansible. For the steps that drive a TripleO deployment it was considered ideal to use traditional OpenStack programming languages like bash and python.

To ensure this tool only uses supported OpenStack and TripleO commands and could provide both scripts and documentation to users, jinja templated bash was chosen.

Make a tool that is attractive to OpenStack developers

It is critical that OpenStack developers can develop and test their patches outside of the OpenStack CI system in the same way that they are tested inside the CI system, developers need to be able to recreate CI results. By abstracting out environments but providing the same inputs one can be assured to get the same results from tripleo-quickstart whether using upstream OpenStack CI or a local tripleo-quickstart deployment on libvirt.

Solve for Scenario #2
  • use composable ansible roles that have limited scope and are reusable. Small tools that do one thing and do one thing well has proven to be a robust model.
  • Allow developers to test their patches, reference Using Quickstart for Development
  • Allow developers to extend code Working With Quickstart Extras to suit their own needs
  • Allow for multiple tripleo deployments on the same virthost which saves on hardware resources.

Footnotes:

[*]Fedora may work but is not guaranteed to work as we do not currently have a CI system that provides Fedora. Changes to TripleO Quickstart are not gated against Fedora hosts or cloud images.
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