Jean-Philippe Evrard 55ce380cc4 Fix Doc8 issue

New manifesto had a doc8 issue and passed lint tests.
This fixes the doc8 issue, a lint test enforcement will be
done in another patch.

Change-Id: Ie50f3351650dd4855de8404d2391b81f9e02bfc5

2018-03-26 07:51:04 +00:00

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OpenStack-Ansible Manifesto

This project will be a Batteries included project. Which means deployer can expect that deploying from any of the named feature branches or tags should provide an OpenStack cloud built for production which will be available at the successful completion of the deployment.

Project scope

However, this project solely focuses on the deployment of OpenStack and its requirements.

This project does not PXE boot hosts. Host setup and lifecycle management is left to the deployer. This project also requires that bridges are setup within the hosts to allow the containers to attach to a local bridge for network access. See also the :dev_docs:Container networking <reference/architecture/container-networking.html>.

Ansible Usage

Ansible provides an automation platform to simplify system and application deployment. Ansible manages systems by using Secure Shell (SSH) instead of unique protocols that require remote daemons or agents.

Ansible uses playbooks written in the YAML language for orchestration. For more information, see Ansible - Intro to Playbooks.

Ansible is a simple yet powerful orchestration tool that is ideally equipped for deploying OpenStack-powered clouds. The declarative nature of Ansible allows the deployer to turn an entire deployment into a rather simple set of instructions.

Roles within the Openstack-Ansible umbrella are built using Ansible best practices and contain namespaced variables that are human understandable. All roles are independant of each other and testable separately.

All roles are built as Galaxy compatible roles even when the given role is not intended for standalone use. While the project will offer a lot of built-in roles the deployer will be able to pull down or override roles with external ones using the built-in Ansible capabilities. This allows extreme flexibility for deployers.

Source based deployments

When the OpenStack-Ansible project was created, it was required to provide a system able to override any OpenStack upstream source code.

This means that OpenStack services and their python dependencies are built and installed from source code as found within the OpenStack Git repositories by default, but allow deployers to point to their own repositories.

This also allows developers to point to their own code for their work.

A source based deployment, for Python-built parts of OpenStack, makes sense when dealing with scale and wanting consistency over long periods of time. A deployer should have the ability to deploy the same OpenStack release on every node throughout the life cycle of the cloud, even when some components are end of life. By providing a repository of the sources, the deployment can be re-created even years after the initial deployment, assuming the underlying operating systems and packages stay the same.

This means that there will never be a time where OpenStack specific packages, as provided by the distributions, are being used for OpenStack services. Third party repositories like CloudArchive and or RDO may still be required within a given deployment but only as a means to meet application dependencies.

Containerized deployments

This project introduces containers as a means to abstract services from one another.

The use of containers allows for additional abstractions of entire application stacks to be run all within the same physical host machines.

The "containerized" applications are sometimes grouped within a single container where it makes sense, or distributed in multiple containers based on application and or architectural needs.

The default container architecture has been built in such a way to allow for scalability and highly available deployments.

The simple nature of machine containers allows the deployer to treat containers as physical machines. The same concepts apply for machine containers and physical machines: This will allow deployers to use existing operational tool sets to troubleshoot issues within a deployment and the ability to revert an application or service within inventory to a known working state without having to re-kick a physical host.

Not all services are containerized: some don't make sense to run within a container. Logic needs to be applied in regards on how services are containerized. If their requirements can't be met due to system limitations, (kernel, application maturity, etc...), then the service is not set to run within a container.

Example of un-containerized services:

Nova compute (for direct access to virtualization devices)
Swift storage (for direct access to drive)

The containers are not a mean of securing a system. The containers were not chosen for any eventual security safe guards. The machine containers were chosen because of their practicality with regard to providing a more uniform OpenStack deployment. Even if the abstractions that the containers provides do improve overall deployment security these potential benefits are not the intention of the containerization of services.

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