Add release workflow

[aliariff]

@cpretzer

Tested manually in my local fork:
https://github.com/aliariff/linkerd2-proxy-init/pull/4/checks?check_run_id=800916941
Using the docker hub registry and my user & pass.
The resulting images are in https://hub.docker.com/r/etni35/proxy-init/tags

This version only can be tested properly when we create a new release tag.

[ihcsim]

@aliariff Thanks for putting this together. Some questions and comments below.

[ihcsim]

TIOLI: consider using --output "type=registry" or just --push. See https://github.com/docker/buildx#registry.

[aliariff]

Possible, but this one just to make a clear distinction between build without pushing and build with pushing.

[ihcsim]

(@cpretzer @olix0r LMKWYT.)

I think this only works OOB with Docker Desktop, right? Specifically, it only works with a Buildx builder that uses the docker-container driver. On my Ubuntu laptop though, the default builder uses the docker driver, which doesn't support multi-platform builds.

Assuming that we want the Makefile to work outside of Docker Desktop and CI too, we should add some instructions like the following to the README:

On some environments where the default Buildx builder doesn't use the docker-container driver, the make images target may return the following error:

$ make images
multiple platforms feature is currently not supported for docker driver. Please switch to a different driver (eg. "docker buildx create --use")
Makefile:57: recipe for target 'images' failed
make: *** [images] Error 1

Use the following commands to create a builder that uses the docker-container driver:

$ docker run --rm --privileged multiarch/qemu-user-static --reset -p yes

$ docker buildx create --name=multiarch --driver=docker-container --platform=linux/amd64,linux/arm64,linux/arm/v7 --use
multiarch

$ docker buildx inspect multiarch --bootstrap

[aliariff]

I agree, instructions in the readme or directly in make help about how to build multi-arch images will be helpful.

[ihcsim]

Maybe we can script it as a different make target (say, make builder), and mention in the README that if one encounters the above error message, run make builder. What do you think of something like:

.PHONY: builder
builder:
   docker run --rm --privileged multiarch/qemu-user-static --reset -p yes
   docker buildx create --name=multiarch-builder --driver=docker-container --platform="${SUPPORTED_ARCHS}" --use
multiarch
   docker buildx inspect multiarch-builder --bootstrap

[aliariff]

That is also possible, I will try it out.

[aliariff]

@ihcsim
is it necessary to run docker run --rm --privileged multiarch/qemu-user-static --reset -p yes?
because in this case, we don't use QEMU, we just utilize golang internal cross-compile features.

[ihcsim]

AIUI, if the Dockerfile has the RUN commands, we will need the qemu in order for those commands to be executed during the multi-arch build.

[ihcsim]

AFAICT, the buildx github action has to do the same thing. See https://github.com/crazy-max/ghaction-docker-buildx/blob/44fd46c7833e095f13bb1d8ace66bd821198bfef/src/main.ts#L24-L38.

[ihcsim]

This will cause CI to run docker buildx build twice, using different --output configuration. I think on CI, we should be able to just use make push.

[aliariff]

Yes, but the second run will be using the cache Overall the whole release workflow finishes in 1 minute.

[ihcsim]

Thanks for adding this section. Can we provide more context around why and when a user will need to run make builder? How about something like:

In some local environments like Ubuntu, where the default Buildx builder uses the docker driver, the make images command might fail with the following error:

$ make images
multiple platforms feature is currently not supported for docker driver. Please switch to a different driver (eg. "docker buildx create --use")
Makefile:57: recipe for target 'images' failed
make: *** [images] Error 1

To fix this, you can create a new Buildx builder instance by running make builder. This command will create a builder that uses the docker-container driver that can build multi-platform images. For more information, see the Buildx builder documentation.

[ihcsim]

LGTM.

[cpretzer]

Very thoughtful work, @aliariff thanks!

[cpretzer]

Is there a reason to leave these comments in?