Adding a new image

Kolla follows Best practices for writing Dockerfiles 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.

Dockerfiles should be placed under the docker directory. OpenStack services should inherit from the provided openstack-base image, and infrastructure services (for example: fluentd) should inherit from base.

Projects consisting of only one service should be placed in an image named the same as that service, for example: horizon. Services that consist of multiple processes generally use a base image and child images, for example: cinder-base, cinder-api, cinder-scheduler, cinder-volume, cinder-backup.

Jinja2 blocks are employed throughout the Dockerfiles to help operators customise various stages of the build (refer to Dockerfile Customisation)

Some of these blocks are free form. However, there is a subset that should be common to every Dockerfile. The overall structure of a Dockerfiles of an OpenStack project base image is as follows:

FROM {{ namespace }}/{{ image_prefix }}openstack-base:{{ tag }}
{% block labels %}
LABEL maintainer="{{ maintainer }}" name="{{ image_name }}" build-date="{{ build_date }}"
{% endblock %}

{% 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 (for example: cinder-base).

It’s probably easiest to identify the most similar service being already provided, copy its Dockerfile structure and amend it to new needs.

Distribution support

By default, every new image should support all supported distributions (CentOS, Debian, Ubuntu) and both x86-64 and aarch64 architectures. Sometimes it is not doable so we have list of unbuildable images for that.

Unbuildable images

In kolla/image/build.py source file we keep a list of images which cannot be built for some distribution/architecture/build-type combinations.

UNBUILDABLE_IMAGES = {
    'aarch64': {
        "bifrost-base",      # someone need to get upstream working first
    },

    'ppc64le': {
        "elasticsearch",     # no binary package
    },

    'binary': {
        "bifrost-base",
        "blazar-base",
    },

    'ubuntu': {
       "qdrouterd",  # There is no qdrouterd package for ubuntu bionic
    },

    'ubuntu+aarch64': {
        "kibana",        # no binary package
    },
}

If your new image has some unbuildable combinations, please add it into proper place in this list. If you are not sure, write it in code review comment and check CI results of your patch.

Note

Please do not overuse this list – it is meant as last hope solution.