Improve tiller-proxy build time with BuildKit

[SimonAlling]

Description of the change

• BuildKit is used for docker build.
• COPY . . is replaced with more explicit directives.
• --mount flag preserves Go build cache between builds.
• Removing the -a flag makes go build use Go build cache.

Benefits

This brought the build time (after modifying the source code) down from 20 seconds to about 5 seconds on my laptop.

Possible drawbacks

• BuildKit requires Docker 18.09 or later. I don't know if building still works on older versions of Docker.

[andresmgot]

Thanks for the improvements @SimonAlling! Unfortunately, it seems that CircleCI doesn't have a version of docker new enough to support buildkit. Maybe you can move that to a variable? so in your local environment, you execute DOCKER_BUILDKIT=1 make kubeapps/tiller-proxy and in the CI we run it without the buildkit?

[SimonAlling]

Thanks for the improvements @SimonAlling! Unfortunately, it seems that CircleCI doesn't have a version of docker new enough to support buildkit. Maybe you can move that to a variable? so in your local environment, you execute DOCKER_BUILDKIT=1 make kubeapps/tiller-proxy and in the CI we run it without the buildkit?

I could definitely do that, but it doesn't seem trivial. In particular, if I remove DOCKER_BUILDKIT=1 in Makefile, it is not possible to make regularly anymore:

$ make kubeapps/tiller-proxy
docker build -t kubeapps/tiller-proxy:dev-2019-12-04T11-54-10-CET --build-arg "VERSION=$(git rev-parse HEAD)" -f cmd/tiller-proxy/Dockerfile .
Sending build context to Docker daemon  64.37MB
Error response from daemon: Dockerfile parse error line 12: Unknown flag: mount

However, judging from the CircleCI output, you're using Docker 18.09, which does support BuildKit:

Build-agent version 1.0.21372-bd73ea34 (2019-12-03T19:06:06+0000)
Docker Engine Version: 18.09.6

So I'm a bit surprised that it doesn't work.

[andresmgot]

Maybe it's something that needs to be enabled in the daemon? This is what I see in the CircleCI logs:

DOCKER_BUILDKIT=1 docker build -t kubeapps/apprepository-controller-ci:build-90c487be9d916722d09c7d7d2a3dec67104beebb --build-arg "VERSION=$(git rev-parse HEAD)" -f cmd/apprepository-controller/Dockerfile .
buildkit not supported by daemon
make: *** [Makefile:22: kubeapps/apprepository-controller] Error 1

[SimonAlling]

Yeah, I saw that as well. I'm not very familiar with CircleCI (and I don't have write access anyway); do you have time to try to find a solution? I think almost everyone working with Kubeapps would benefit from this PR.

[andresmgot]

It seems it's possible to enable it from the comment here: https://ideas.circleci.com/ideas/CCI-I-1003

Can you replace in .circleci/config.yaml the line - setup_remote_docker with:

      - setup_remote_docker:
          version: 18.09.3

That should work 🤞

[andresmgot]

Great, thanks!