Add new Kaniko Dockerfile for PDNS builder

[aerique]

(I'm not sure @wojas needs to review this. Possibly the Kaniko build process was added after @pieterlexis took ZoneControl over.)

A custom Kaniko image for PDNS Builder, because the official Kaniko debug image only offers Busybox and the PDNS Builder also needs Bash, Git, Perl, rsync and perhaps more.

For now we put it besides Dockerfile-kaniko until it is clear that one can be removed.

AFAIK this file is only used for ZoneControl builds but I'm not entirely sure, that's why I do not want to remove Dockerfile-kaniko yet.

This new Dockerfile has been successfully used for the latest ZoneControl builds as part of the process to fix the flaky builds.

It is available at https://hub.docker.com/repository/docker/powerdns/kaniko-pdns-builder/ which is where the ZoneControl builds pull it from.

[Habbie]

AFAIK this file is only used for ZoneControl builds but I'm not entirely sure, that's why I do not want to remove Dockerfile-kaniko yet.

Do note that all users of pdns-builder import it as a git submodule, which is tied to a git commit. Removing things will not randomly break users; they'll find out when they try to bump to a new version, at which point we can revisit, restore, etc.

I'm not proposing "just edit the file", because that might lead to invisible and subtle problems. I am proposing "add the new file, and delete the old file, and users will notice, very clearly, at some point".

[Habbie]

Do note that all users of pdns-builder import it as a git submodule

He said, before reading the bit about "it's published to Docker Hub".

[wojas]

I would like to get rid of Kaniko in all our build systems eventually, but preferably without causing any external users too much inconvenience. Having two of these Dockerfiles just seems confusing.

Perhaps remove the old Dockerfile, move the new one to an examples subdir and add a Kaniko deprecation warning to the README?

Why would anyone want to continue to use the old Dockerfile-kaniko?

[aerique]

Why would anyone want to continue to use the old Dockerfile-kaniko?

I'm just not 100% sure the ZoneControl build process is the only one using it.

[Habbie]

I'm just not 100% sure the ZoneControl build process is the only one using it.

While I thought I laid out a safe alternative path above (and was wrong), this is not a thing that worries me. I suggest just updating the existing file & docker hub image.

[aerique]

I'm assuming I can ignore the failed tests?

[wojas]

I'm assuming I can ignore the failed tests?

They are not related to this PR, but do need fixing.

[Habbie]

I took the liberty of rebasing this, although I'm not sure we need it any more.

[aerique]

I took the liberty of rebasing this, although I'm not sure we need it any more.

ZoneControl is currently not using this.

[Habbie]

let's close this and at some point remove it all