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Display additional details for container registry tags that point to manifest lists/indexes

Context

Part of Improve container registry multi-architecture i... (&11952).

Task

Using the below screenshot from https://gitlab.com/jdrpereira/multi-arch/container_registry/1245177...

image

... and knowing that tag 1.0.0 points to a manifest list/index, when expanding the details of this tag, we should see the digest, platform/architecture, and platform/OS of the manifests referenced by that list/index.

In the example above, we'd see that the list/index tagged with 1.0.0 references two manifests, one with digest sha256:dbd3f975d9c1d9727b3fcc3954c006f933319c1bc278cc304d21b9127bf2cabd (tagged as 1.0.0-amd64) and another with digest sha256:b41fa10fdc1b5f3183d1f310066923a05af8c4e44500e2bb059ef4b956408468 (tagged as 1.0.0-arm64v8). By looking at the payload of the underlying list/index, we also know that the former targets the linux/amd64 OS/architecture, and the latter linux/arm64.

So when expanded, in the tag details of 1.0.0, we'd see a list with something like this below the Manifest digest: row (remember, there is no Configuration digest: for lists/indexes - #408863 (closed)):

References:
   - sha256:b41fa10fdc1b5f3183d1f310066923a05af8c4e44500e2bb059ef4b956408468 [linux/amd64]
   - sha256:b41fa10fdc1b5f3183d1f310066923a05af8c4e44500e2bb059ef4b956408468 [linux/arm64]

Note that we're not including the tag names 1.0.0-amd64 and 1.0.0-arm64v8 in the information above. Although after &10208 (closed) the Rails frontend/backend will have a list of tags alongside their manifest digest (based on which we could look up each of the digests above to find out their tag names, and then display them in the info above), we're using paginated requests, so a lookup with just this information would only be possible if both the list/index and all referenced images were on the same page.

We'll leave this cross-referencing for a future iteration, as we'll have to build additional discoverability capabilities into the registry API to reverse lookup tags.

Implementation

To accomplish this we'll need to:

  1. rails frontend: When expanding the details of tag X that points to a list/index, ask Rails for its details. This should ideally happen on a separate page (Create separate page to show container image ta... (#497121)). Instead, and as a possible intermediate step, we may be able to trigger this query when expanding the current accordion icon/pane.

  2. rails backend: When receiving the above request, query a new registry API (Add single tag details API endpoint (container-registry#1393 - closed)) to obtain the details for the tag, which will include the target OS/platform.

  3. rails frontend: With the new information in hand, render it in the UI.

Note: While this requires a second request to obtain the additional details, manifest lists/indexes are the minority, so this is expected to only be required for a small portion of the tags. If this changes in the future, and/or performance becomes a concern, we can work on expanding the tags list API in the registry to account for these extra details (#369852). However, at this time, that would be far more complex that the proposed solution.

Edited by João Pereira