openstack/openstack-helm
Code Issues Proposed changes
5ad407ab0e
openstack-helm/doc/source/devref/images.rst
Steve Wilkerson 9736f5f544 Update kubernetes-entrypoint image reference 
This updates the kubernetes-entrypoint image reference to consume
the publicly available kubernetes-entrypoint image that is built
and maintained under the airshipit namespace, as the stackanetes
image is no longer actively maintainedy

Depends-On: https://review.opendev.org/688435

Change-Id: I8e76cdcc9d4db8975b330e97169754a2a407341f
Signed-off-by: Steve Wilkerson <sw5822@att.com>
2019-10-21 13:58:22 +00:00

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Images

The project's core philosophy regarding images is that the toolsets required to enable the OpenStack services should be applied by Kubernetes itself. This requires OpenStack-Helm to develop common and simple scripts with minimal dependencies that can be overlaid on any image that meets the OpenStack core library requirements. The advantage of this is that the project can be image agnostic, allowing operators to use Stackanetes, Kolla, LOCI, or any image flavor and format they choose and they will all function the same.

A long-term goal, besides being image agnostic, is to also be able to support any of the container runtimes that Kubernetes supports, even those that might not use Docker's own packaging format. This will allow the project to continue to offer maximum flexibility with regard to operator choice.

To that end, all charts provide an images: section that allows operators to override images. Also, all default image references should be fully spelled out, even those hosted by Docker or Quay. Further, no default image reference should use :latest but rather should be pinned to a specific version to ensure consistent behavior for deployments over time.

Today, the images: section has several common conventions. Most OpenStack services require a database initialization function, a database synchronization function, and a series of steps for Keystone registration and integration. Each component may also have a specific image that composes an OpenStack service. The images may or may not differ, but regardless, should all be defined in images.

The following standards are in use today, in addition to any components defined by the service itself:

  • dep_check: The image that will perform dependency checking in an init-container.
  • db_init: The image that will perform database creation operations for the OpenStack service.
  • db_sync: The image that will perform database sync (schema initialization and migration) for the OpenStack service.
  • db_drop: The image that will perform database deletion operations for the OpenStack service.
  • ks_user: The image that will perform keystone user creation for the service.
  • ks_service: The image that will perform keystone service registration for the service.
  • ks_endpoints: The image that will perform keystone endpoint registration for the service.
  • pull_policy: The image pull policy, one of "Always", "IfNotPresent", and "Never" which will be used by all containers in the chart.

An illustrative example of an images: section taken from the heat chart:

images:
  tags:
    bootstrap: docker.io/openstackhelm/heat:ocata
    db_init: docker.io/openstackhelm/heat:ocata
    db_sync: docker.io/kolla/ubuntu-source-heat-api:ocata
    db_drop: docker.io/openstackhelm/heat:ocata
    ks_user: docker.io/openstackhelm/heat:ocata
    ks_service: docker.io/openstackhelm/heat:ocata
    ks_endpoints: docker.io/openstackhelm/heat:ocata
    api: docker.io/kolla/ubuntu-source-heat-api:ocata
    cfn: docker.io/kolla/ubuntu-source-heat-api:ocata
    cloudwatch: docker.io/kolla/ubuntu-source-heat-api:ocata
    engine: docker.io/openstackhelm/heat:ocata
    dep_check: quay.io/airshipit/kubernetes-entrypoint:v1.0.0
  pull_policy: "IfNotPresent"

The OpenStack-Helm project today uses a mix of Docker images from Stackanetes and Kolla, but will likely standardize on a default set of images for all charts without any reliance on image-specific utilities.