kolla-ansible/doc/CONTRIBUTING.rst

How To Contribute

Basics

1. Our source code is hosted on OpenStack Kolla Git. Bugs should be filed on launchpad.
2. Please follow OpenStack Gerrit Workflow to to contribute to Kolla.
3. Note the branch you're proposing changes to. master is the current focus of development. Kolla project has a strict policy of only allowing backports in stable/branch, unless when not applicable. A bug in a stable/branch will first have to be fixed in master.
4. Please file a launchpad blueprint for any significant code change and a bug for any significant bug fix or add a TrivialFix tag for simple changes. See how to reference a bug or a blueprint in the commit message here
5. TrivialFix tags or bugs are not required for documentation changes.

Development Environment

Please follow our quickstart to deploy your environment and test your changes.

Please use the existing sandbox repository, available at https://git.openstack.org/cgit/openstack-dev/sandbox, for learning, understanding and testing the Gerrit Workflow.

Adding a new service

Kolla aims to both containerise and deploy all services within the OpenStack "big tent". This is a constantly moving target as the ecosystem grows, so these guidelines aim to help make adding a new service to Kolla a smooth experience.

The image

Kolla follows Docker best practices (https://docs.docker.com/engine/userguide/eng-image/dockerfile_best-practices/) when designing and implementing services where at all possible.

We use jinja2 templating syntax to help manage the volume and complexity that comes with maintaining multiple Dockerfiles for multiple different base operating systems.

Images should be created under the docker directory. OpenStack services should inherit from the provided openstack-base image, while supporting and infrastructure services (e.g. mongodb) should inherit from base.

Services consisting of only one service should be placed in an image named the same as that service, e.g. horizon. Services that consist of multiple processes generally use a base image and child images, e.g. glance-base, glance-api, and glance-registry.

Jinja2 'blocks' are employed throughout the Dockerfile's to help operators customise various stages of the build (refer to http://docs.openstack.org/developer/kolla/image-building.html?highlight=override#dockerfile-customisation)

Some of these blocks are free form however, there are a subset that should be common to every Dockerfile. The overall structure for a multi container service is as follows:

FROM {{ namespace }}/{{ image_prefix }}openstack-base:{{ tag }}
MAINTAINER {{ maintainer }}

{% import "macros.j2" as macros with context %}

<< binary specific steps >>

<< source specific steps >>

<< common steps >>

{% block << service >>_footer %}{% endblock %}
{% block footer %}{% endblock %}
{{ include_footer }}

Note

The generic footer block {% block footer %}{% endblock %} should not be included in base images (e.g. glance-base).

{{ include_footer }} is legacy and should not be included in new services, it is superseded by {% block footer %}{% endblock %}

Orchestration

As of the Newton release there are two main orchestration methods in existence for Kolla, Ansible and Kubernetes. Ansible is the most mature and generally regarded as the reference implementation.

When adding a role for a new service in Ansible, there are couple of patterns that Kolla uses throughout that should be followed.

• The sample inventories

  Entries should be added for the service in each of ansible/inventory/multinode and ansible/inventory/all-in-one.

• The playbook

  The main playbook that ties all roles together is in ansible/site.yml, this should be updated with appropriate roles, tags, and conditions. Ensure also that supporting hosts such as haproxy are updated when necessary.

• The common role

  A common role exists which sets up logging, kolla-toolbox and other supporting components. This should be included in all services within meta/main.yml of your role.

• Common tasks

  All services should include the following tasks:

  • do_reconfigure.yml : Used to push new configuration files to the host and restart the service.
  • pull.yml : Used to pre fetch the image into the Docker image cache on hosts, to speed up intial deploys.
  • upgrade.yml : Used for upgrading the service in a rolling fashion. May include service specific setup and steps as not all services can be upgraded in the same way.

Other than the above, most roles follow the following pattern:

-  ``Register`` : Involves registering the service with Keystone, creating endpoints, roles,
  users, etc.

-  ``Config`` : Distributes the config files to the nodes to be pulled into the container on
  startup.

- ``Bootstrap`` : Creating the database (but not tables), database user for the service,
  permissions, etc.

- ``Bootstrap Service`` : Starts a one shot container on the host to create the database tables,
  and other initial run time config.

- ``Start`` : Start the service(s).