👋 Hi I’m interested in addressing a docker/buildx issue 19994 but need some guidance on what a proper fix would actually look like. Theres a lot more context in this thread on the specifics of the problem, but it boils down to I’d like

pants package

and

pants publish

to be semantically correct for cross platform docker builds when using buildx. buildx makes that awkward by forcing the use of a single command to both package and publish in a single step https://pantsbuild.slack.com/archives/C046T6T9U/p1711423114773989?thread_ts=1711401515.193319&cid=C046T6T9U

Hi! 👋 Awesome to get this addressed. I'll drop a few thoughts/ideas/notes on what I think this could look like, for inspiration. (caveat: I've not used Docker for a long time, so the whole buildx thing is new territory for me, so my ideas are merely guided by old knowledge and the various tidbits provided in the comments here about how it works..) First, I would prefer it if we can avoid adding dedicated targets to solve this; which I think we can. I read the comment about building a simplified (single platform) image for testing (that would be when using

pants package

) and then building (and pushing) the multi platform image when doing

pants publish

. To me this makes sense, and is what I'll go for in my following notes.. Notes: • Tweak

pants package

to only build for the local platform when using buildx (i.e. ignore the build_platforms field; anything else?) • Split the

build_docker_image

rule so the we can re-use the part of getting the

Process

request for building the image as a rule helper. • For

pants publish

when using buildx, use the build image rule helper to get the

Process

request for building, providing a flag to indicate we want to build for and push, a multi platform image. I think that's pretty much it at a high level. Thoughts?

That all makes sense to me, I’ll put together a draft so we can have a reference point to talk about

I think a draft would definitely be helpful. If i'm understanding this correctly, this is all for the case where we don't want to use the containerd-snapshotter, which is currently the happy path for Pants-docker-buildx currently? I think

pants package

should build for the platforms specified when run locally - that is a feature of buildx - to support building images for different platforms locally? Another option might be to export the images to file (output type = 'image' from memory? ) and push them from there with publish? But I do like the suggestion of having

publish

do build and publish in the case of buildx - probably makes things simpler in terms of publish not having to expect already built images laying around somewhere.

I’ve got a very rough draft ready to discuss https://github.com/pantsbuild/pants/pull/20728