[Pulp-list] Do you remove docker content from the repositories?

[Simon Baatz]

On Tue, Jul 16, 2019 at 09:28:38PM +0200, Ina Panova wrote:
>    Hello community,
>    we are trying to gather feedback on docker content removal behaviour in
>    Pulp3.
>    Here are the use cases we came up with, please share your thoughts and
>    expectations.
>    When it is desired to remove docker content from a repo, the
>    expectations are that:
>       * when a docker image manifest is removed, all its blobs( not
>    referenced by other image manifests) are removed as well. Also tags
>    that were referencing this manifest will be removed.

What should happen to manifest lists that reference the manifest? Are
those removed as well? (and by extension, the tags pointing to them)

>       * When a docker manifest list is removed, all its manifests( not
>    referenced by other manifests lists and not tagged) are removed as
>    well. Furthermore, same story with the blobs. Also tags that were
>    referencing this manifest list will be removed.
>       *When a tag is removed , only tag is removed.

Yes, that makes sense.  I know a repo manager that removes the
manifest list/manifest/blobs when the last tag is removed.  I don't
like this behavior because it causes problems when adopting a
workflow without tags (i.e.  using content adresses only).

However, users may expect this recursive behavior as the tag may be
the only identifier they are aware of.

>    Do you find this recursive removal behaviour useful and expect it work
>    the way it got described above? Or simple removal makes more sense,
>    e.g. just image manifest and its tag are removed?

I find the recursive removal very useful. As a user I expect Pulp to
know the details of the artifact structure and do the "right thing".

I am wondering whether we should only remove recursively "down" the
reference hierarchy, but not up. AFAIK, the references are:

tag -> manifest list -> manifest -> blob
tag ------------------>

Removal would work as follows: You can remove an artifact if no
artifact on a higher level references it. If it can be removed, all
(otherwise unused) artifacts on lower levels are deleted recursively.

For example, you cannot delete a manifest that is still referenced by
a manifest list or tag.