Adding Docker Hub OCI repository for multiple charts

[heruan]

Hello! I'm publishing my charts to Docker Hub as described here: https://helm.sh/docs/topics/registries/ e.g.

helm push foo-0.1.0.tgz oci://registry-1.docker.io/heruan
helm push bar-0.1.0.tgz oci://registry-1.docker.io/heruan

and I see the charts published in Docker Hub.

Now I'd like to add this chart registry as a repository in ArtifactHUB, so I create a new repository targeting oci://registry-1.docker.io/heruan but I soon get this error message:

error getting repository remote digest: GET https://registry-1.docker.io/v2/heruan/tags/list?n=1000: UNAUTHORIZED: authentication required; [map[Action:pull Class: Name:heruan Type:repository]]

So I now wonder, is it possible to use OCI registries such as Docker Hub to act as repositories for Helm charts in ArtifactHUB?

[tegioz]

Hi @heruan 👋

Yes, it's possible, but you need to add one repository per chart. You can find more information about this in the Helm charts repositories guide.

[heruan]

Thank you @tegioz for the quick answer! Oh, I stumbled upon that guide but I didn't get I'd need one repository per chart. Is that a technical limitation? It kind of defeats the purpose of having a repository if I need one for each chart 🤔

[tegioz]

No worries!

The reason it works this way is a combination of how Helm OCI based repositories work (please see these issues for more context) and that the OCI distribution spec does not (well, it didn't when this feature was added 😅) define a mechanism to list all references for a given namespace. We discussed this in more detail some time ago.

Artifact Hub needs an entry point to start indexing content, like it does on HTTP based Helm charts repositories using the index.yaml file. But AFAIK we cannot neither get this index from a special OCI reference nor discover them via OCI registry APIs. So unfortunately we need to ask publishers to provide this information to us. Hopefully this will improve over time 🙂

For OLM operators, for example, there is a special OCI reference (the catalog), that acts as an index of all the content available. This allows us to index multiple OLM operators in an OCI registry using a single repository.