base_path uniqueness constraint prevents syncing the same image from multiple remote registries

[Katakam-Rakesh]

Summary

When the same container image path (e.g. library/mysql) is synced from
multiple remote registries, Pulp rejects the second and subsequent
distributions with a base_path uniqueness error.

Tags from the same image across different registries cannot be served
under a single distribution.

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Current Behaviour

Remote registry	Image	Derived base_path	Result
docker.io	library/mysql	library/mysql	✅ Created
100.10.1.114:443	library/mysql	library/mysql	❌ Rejected
100.10.1.114:3445	library/mysql	library/mysql	❌ Rejected

Error returned:

{"base_path": ["This field must be unique."]}

Note: Multiple tags of the same image from the same registry sync
and distribute correctly. The issue only occurs when different remote
registries provide tags for the same image path.

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Expected Behaviour

If tags are coming from different registries for the same image, Pulp
should support serving them through the same distribution with the same
base_path. The unified tag list from all upstream sources should be
accessible to clients under a single namespace.

---

Reproduction Steps

# 1. Create remote A (public registry)
pulp container remote create \
  --name "mysql-dockerhub" \
  --upstream-name "library/mysql" \
  --url "https://registry-1.docker.io" \
  --include-tags "8.0 8.4"

# 2. Sync remote A → repo A
pulp container repository create --name "mysql-a"
pulp container repository sync --name "mysql-a" --remote "mysql-dockerhub"

# 3. Create distribution A  →  succeeds
pulp container distribution create \
  --name "mysql-dist" \
  --base-path "library/mysql" \
  --repository "mysql-a"

# 4. Create remote B (private registry, different tags)
pulp container remote create \
  --name "mysql-private" \
  --upstream-name "library/mysql" \
  --url "https://100.10.1.114:443" \
  --include-tags "8.0-custom 8.4-patched"

# 5. Sync remote B → repo B
pulp container repository create --name "mysql-b"
pulp container repository sync --name "mysql-b" --remote "mysql-private"

# 6. Create distribution B  →  FAILS
pulp container distribution create \
  --name "mysql-dist-private" \
  --base-path "library/mysql" \
  --repository "mysql-b"
# ERROR: {"base_path": ["This field must be unique."]}

---

Related Issues

• Expose Image Tags in Pulp Container Distribution / CLI #2164 – Expose Image Tags in Pulp Container Distribution / CLI
  — that issue added support for exposing tags within a single
  remote/repository. This issue extends the same need across multiple
  remotes/registries for the same image path.

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Use Case

In enterprise environments it is common to mirror the same image from
multiple upstream registries (public + private, or primary + DR site) and
present them behind a single namespace to consumers. Currently there is
no way to achieve this in Pulp when the image path is identical across
registries.

[gerrod3]

@Katakam-Rakesh Yes, the current way you are trying to merge public and private registries is not allowed in Pulp, but there are other ways you can achieve the same outcome.

1. Sync both images into the same repository. Since they are both of the same image and you want them to be served under the same name, mixing them into the same repo under one distribution would be the easiest solution.
2. Sync them into separate repos, them mix them together into a third repo that is then distributed. The copy tag workflow would be what you would want to use: https://pulpproject.org/pulp_container/docs/user/guides/manage-image/#copy-tags