cross-repository blob mount with absent from parameter (spec compliant)

[thibaut-lo]

the OCI Distribution Spec mentions the ability to treat the from repository name as optional when mounting a blob from another repository.

The registry MAY treat the from parameter as optional, and it MAY cross-mount the blob if it can be found.

in endpoint /v2/<name>/blobs/uploads/?mount=<digest>&from=<other_name> endpoint

Is that in the roadmap to provide the configuration to remove the need to specify the from parameter? E.g. /v2//blobs/uploads/?mount=
and return 201 Created if the repository is found for that user in another repository in the registry and the mount performed.

References:

• https://github.com/opencontainers/distribution-spec/blob/main/spec.md#mounting-a-blob-from-another-repository
• Pull request that amended that line: Allow for automatic content discovery for cross-mounting blobs opencontainers/distribution-spec#275)

[rchincha]

@thibaut-lo thanks for pointing this out. Just curious where this requirement is coming from - are any client tools breaking?

[thibaut-lo]

Apologies for the delay in replying. @rchincha

Just curious where this requirement is coming from

• https://github.com/opencontainers/distribution-spec/blob/main/spec.md#mounting-a-blob-from-another-repository
• Original MR introducing it: Allow for automatic content discovery for cross-mounting blobs opencontainers/distribution-spec#275

Are any client tools breaking ?

No. My organization has been looking for a registry implementating that feature, and zot would have a been a good choice for us if it had been implementing it. At this an optional feature for registries to implement, zot is not breaking the specs, it is rather not implementing an optional feature.

Hence my question:

Is that in the roadmap to provide the configuration to remove the need to specify the from parameter? E.g. /v2//blobs/uploads/?mount=
and return 201 Created if the repository is found for that user in another repository in the registry and the mount performed.

Many thanks for the insights :)

[rchincha]

@thibaut-lo If "dedupe" is enabled in configuration, then blob deduplication happens globally removing the need to issue an explicit blob mount.

(pseudo code)
PUSH /v2/repo1/blobs/blobA -> success
GET /v2/repo2/blobs/blobA -> success although didn't actually push it here (once past authN/authZ of course)

[thibaut-lo]

That's cool, thanks!