Open Stack

Hello Stackers,

As you may have seen, the TripleO project has been testing the idea of
building container images using a simplified toolchain [0]. The idea is to
build smaller, more easily maintained images to simplify the lives of
TripleO consumers. Since TripleO's move to containers, the project has been
leveraging Kolla to provide Dockerfiles, and while this has worked, TripleO
has created considerable tooling to bend Kolla images to its needs. Sadly
this has resulted in an image size explosion and the proliferation of
difficult to maintain tools, with low bus factors, which are essential to
the success of the project. To address the risk centered around the TripleO
containerization story, we've drafted a spec [0], which we believe outlines
a more sustainable future. In this specification, we've designed a new,
much more straightforward, approach to building container images for the
TripleO project. The "simple container generation," specification does not
intend to be a general-purpose tool used to create images for the greater
OpenStack community, both Loci and Kolla do that already. This effort is to
build containers only for TripleO using distro provided repositories, with
distro maintained tooling. By focusing only on what we need, we're able to
remove all general-purpose assumptions and create a vertically integrated
stack resulting in a much smaller surface area.

To highlight how all this works, we've put together several POC changes:
* Role and playbook to implement the Containerfile specification [1].
* Tripleoclient review to interface with the new role and playbook [2].
* Directory structure for variable file layout [3].
* To see how this works using the POC code, building images we've tested in
real deployments, please watch the ASCII-cast [4].
* Example configuration file examples are here [5][6][7].

A few examples of size comparisons between our proposed tooling versus
current Kolla based images [8]:
  - base:
      + Kolla: 588 MB
      - new: 211 MB  # based on ubi8, smaller than centos8
  - nova-base:
      + Kolla: 1.09 GB
      - new: 720 MB
  - nova-libvirt:
      + Kolla: 2.14 GB
      - new: 1.9 GB
  - keystone:
      + Kolla: 973 MB
      - new: 532 MB
  - memcached:
      + Kolla: 633 MB
      - new: 379 MB

While the links shown are many, the actual volume of the proposed change is
small, although the impact is massive:
* With more straightforward to understand tools, we'll be able to get
broader participation from the TripleO community to maintain our
containerization efforts and extend our service capabilities.
* With smaller images, the TripleO community will serve OpenStack deployers
and operators better; less bandwidth consumption and faster install times.

We're looking to chart a more reliable path forward, and making the TripleO
user experience a great one. While the POC changes are feature-complete and
functional, more work is needed to create the required variable files;
however, should the proposed specification be ratified, we expect to make
quick work of what's left. As such, if you would like to be involved or
have any feedback on anything presented here, please don't hesitate to
reach out.

We aim to provide regular updates regarding our progress on the "Simple
container generation" initiative, so stay tuned.

Thanks,

Kevin and Emilien

[0] https://review.opendev.org/#/c/723665/
[1] https://review.opendev.org/#/c/722557/
[2] https://review.opendev.org/#/c/724147/
[3] https://review.opendev.org/#/c/722486/
[4] https://files.macchi.pro:8443/demo-container-images/
[5] http://paste.openstack.org/show/792995/
[6] http://paste.openstack.org/show/792994/
[7] http://paste.openstack.org/show/792993/
[8]
https://4ce3fa2efa42bb6b3a69-771991cd07d409aaec3e4ca5eafdd7e0.ssl.cf2.rackcdn.com/724436/2/check/tripleo-build-containers-centos-8/78eefc3/logs/containers-successfully-built.log

Kevin Carter
IRC: kecarter
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