ArgoCD expects index.yaml for Helm Chart on OCI Registry when using SemVer Ranges

[rowi1de]

Discussed in #9509

^{Originally posted by rowi1de May 25, 2022}

• For Git based you are able to point an Application to a branch or ref

  source:
    repoURL:  https://github.com/rowi1de/graphql-reactive
    targetRevision:  HEAD

• ArgoCD will always deploy the latest commit / revision

• For Helm in OCI you need to specify a fixed Version of the Helm Chart in the Application

 project: my-helm-chart
 source:
   repoURL: ghcr.io/rowi1de/graphql-reactive
   targetRevision:  0.0.17

• For Classic Helm Registries you can use SemVer ranges: https://argo-cd.readthedocs.io/en/stable/user-guide/tracking_strategies/

  project: my-helm-chart
  source:
    repoURL: ghcr.io/rowi1de/graphql-reactive
    targetRevision: 0.0.*

• This doesn't work for Helm on OCI, as ArgoCD expect Index.yaml which is only available for classic helm repositories.

  argo-cd/reposerver/repository/repository.go

  Line 1663 in 7faae31

  index, err := helmClient.GetIndex(noRevisionCache)

• OCI doesn't allow discovering versions, but it can list tags: https://github.com/opencontainers/distribution-spec/blob/main/spec.md#content-discovery
• Also for helm pull, version ranges are supported

helm pull oci://ghcr.io/rowi1de/graphql-reactive/graphql-reactive --version '0.0.*'
Pulled: ghcr.io/rowi1de/graphql-reactive/graphql-reactive:0.0.17

helm pull oci://ghcr.io/rowi1de/graphql-reactive/graphql-reactive --version '0.1.*'
Pulled: ghcr.io/rowi1de/graphql-reactive/graphql-reactive:0.1.2

• My workflow is as follows

  • CI with GitHub Actions
    • Tag & Push Docker Image with commit-id
    • Increment Patch Version of the Helm Chart based on SemVer
    • Publish new Helm Chart to Github Packages as OCI Image
    • Point Argo CD to the OCPI Image / Helm Chart

• One Note: I'm currently not pushing the modified Chart.yaml from the GitHub Action Release workflow, so the committed Chart.yaml will always contain a wrong version

Or hoping for helm helm/helm#11000

[sunib]

Thanks for this elaborate bug. I'm just walking into the same problem while trying to run my application from an OCI helm chart repo (acr).

When I use a fixed version all works: anything range like is failing.

This is a shame since I now need to update my application by hand on every change.

[rowi1de]

@sunib welcome 🙌🏻 if more people start to use OCI it can get more popular. 🤞 here ... let's see what happens. The issue mainly affects or originates from OCI & Helm and a small bug in ArgoCD (index.yaml)

I'm not 100% if the listing of Tags is OCI standard or depends on the registry.

[alexef]

Please see my solution in #10641 - successfully tested on our set up (using AWS ECR as OCI repo for helm) trying to find a reviewer 🙏