[CI:TOOLING] Track image IDs instead of tar exports

[cevich]

Previously all container builds run by the Makefile managed them based
on presence/absence of a docker-archive tar file. Producing these
exports is time-consuming and ultimately unnecessary extra work. The
tar files are never actually consumed in a meaningful way by any other
targets. Further, most of the container builds in CI run in parallel,
simply throwing away the tar when finished.

Fix this by switching to management based on image-ID files instead.
The only exception is the imgts image and images which are based on
it. For those, some special handling is required (already done by the
CI build script), so some comments were added to assist.

Also, remove the bench_stuff target entirely as this has long since
been retired.

[cevich]

I think this is ready for review. Container image build times with these changes:

imgts 06:47
ccia 2:23
gcsupld 1:21
get_ci_vm 1:21
imgobsolete 1:21
imgprune 1:21
orphanvs 1:21

Compared to a past build:

IMGTS 08:13
ccia 02:21
gcsupld 09:59
get_ci_vm 01:43
imgobsolete 09:36
imgprune 09:32
orphanvms 09:46

Likely the biggest build-time boost is the result of pushing/pulling the imgts, as it's used as a base-image for most of the others.

[cevich]

Ed and/or Paul, if you have time would you mind giving this a look-through?

[edsantiago]

This is completely over my head, but LGTM in theory with one question

[edsantiago]

Not worth a repush on its own

[cevich]

Oh whups. I can fix that NP, this PR builds quickly.

[edsantiago]

I don't understand this. Does this magic image have an entrypoint or command defined for when it's invoked without args? If so, did you confirm that the true here actually overrides the default? Because sometimes you can override via command-line, and sometimes you need to specify --entrypoint. (I could figure this out myself given enough time but my brain hurts from this). Anyhow, CI got skipped for this PR so I can't verify tests.

[cevich]

This is intended for interactive-use by humans, and should probably be documented in the README.md. The entrypoint is simply the default 'bash'. It's for developing/debugging the dockerfile-based Cirrus-CI tasks, since the image-build happens w/in Cirrus (i.e. it's never pushed anywhere):

(.cirrus.yml)

...cut...
image_builder_task:
    ...cut...
    container:
        dockerfile: "image_builder/Containerfile"
    ...cut...
...cut...

Anyhow, CI got skipped

Careful, CI wasn't entirely skipped. The builds and new test tasks did run 😉

I'll add some quick docs for this.

---

FWIW, the image_builder_debug target (also intended for humans) is already documented.

[Luap99]

I don't feel qualified to review this. There is a lot of makefile logic that I cannot follow right now. Anyhow using image ids to pass the images around to other tasks seems better

[cevich]

Thanks guys. I understand make was probably not the best choice originally. But I'm hopeful these simplifications, speedups and doc updates are at least a small improvement.