ZUI: use logos distributed as OCI artifacts using the referrers API

[andaaron]

[AlexGustafsson]

Hey, @andaaron. I've seen a few different issues covering how Zot could be identifying logos for images and artifacts. Initially an annotation seemed to be in use, but from what I can tell that support is only mentioned in the UI these days, with the actual APIs no longer exposing the logo field:

Zui:

zui/src/utilities/objectModels.js

Line 15 in 930ae7e

logo: responseRepo.NewestImage?.Logo,

Zot:
https://github.com/project-zot/zot/blob/ab43515c888e6f7e80f9daa44985e2090771be49/pkg/common/model.go#L35-L56

Since the OCI referrers APIs was released the intention has been in using it, if I'm not mistaken. Do you know if there's been any process in the intended design? Is the intention for the UI to identify and fetch the logo based on the manifests or would the Zot backend react on the changes like in the previous PRs (project-zot/zot#833, project-zot/zot#1018)?

[andaaron]

Hi @AlexGustafsson. The zui implementation above is based on project-zot/zot#833. The annotation value coming from the manifest is not an url, but the logo itself.

The alternatives would have been based on OCI artifacts.
project-zot/zot#1018 partially implements validation for the presence of such an artifact on the zot server for an image, but there were several open questions such as:

• Should the logo be part of the artifact manifest as an annotation, or the artifact config (theoretically OCI artifacts can have alternative media types for configs), or a layer? If it is a layer, should be be archived or not?
• Should zot be the one reading the artifact and sending it to zui in the same field used in Support storing image logos as manifest annotations zot#833, or should zui call the referrers API to get the artifact and read it?

Since there was no consensus within the team at the time, and this was not urgent, we decided to wait and see what the OCI community was going to do for this use case and implement that.
2 years later and based on opencontainers/image-spec#1231, it looks like the issue is not settled in the community.