oci_image uses significantly more disk space than container_image from rules_docker

[SanjayVas]

oci_image appears to copy all base image layer blobs to its Bazel output tree. Additionally it temporarily takes up even more space due to running a separate registry for each target.

I believe container_image from rules_docker only has the created layer(s) in its output.

Anecdotally, this blew up my CI. My compressed Bazel output cache went from ~3 GiB to ~20 GiB when migrating from rules_docker to rules_oci.

[alexeagle]

I think this is fixed by that #440 - @SanjayVas if you have time, could you patch that in and verify?

[thesayyn]

@alexeagle partially. we still copy blobs from base image (copy_to_directory) into oci_image's oci-layout (treeartifact) which causes duplication of the blobs.
we should symlink blobs from base image into the oci_image's output to prevent copies.

[thesayyn]

but that's a bigger fix and i don't have time to contribute. happy to review if somebody else is willing to contribute it.

[SanjayVas]

I think this is fixed by that #440 - @SanjayVas if you have time, could you patch that in and verify?

Sorry, the migration to rules_oci was prefactoring for migrating our tree of repos to Bzlmod. I can possibly try after that is done, but it will of course be easier if a version with that change has been published to BCR.

[thesayyn]

Okay now that #560 #559 landed, this can be closed.