.. _CONTRIBUTING:

=================
How To Contribute
=================

Basics
======

#. Our source code is hosted on `OpenStack Kolla Git`_. Bugs should be filed on
   launchpad_.

#. Please follow OpenStack `Gerrit Workflow`_ to contribute to Kolla.

#. 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``.

#. Please file a launchpad_ blueprint for any significant code change and a bug
   for any significant bug fix.  See how to reference a bug or a blueprint in
   the commit message here_. For simple changes, contributors may optionally
   add the text "TrivialFix" to the commit message footer to indicate to
   reviewers a bug is not required.

.. _OpenStack Kolla Git: https://git.openstack.org/cgit/openstack/kolla/
.. _launchpad: https://bugs.launchpad.net/kolla
.. _here: https://wiki.openstack.org/wiki/GitCommitMessages

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

.. _Gerrit Workflow: http://docs.openstack.org/infra/manual/developers.html#development-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 }}

    {% block << service >>_header %}{% endblock %}

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

    << binary specific steps >>

    << source specific steps >>

    << common steps >>

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

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