[Pulp-dev] the "relative path" problem

Sat Apr 25 11:02:05 UTC 2020

I had a chance to think about this some more yesterday and wanted to email
out my thoughts. I also think that this change sounds scary and will have a
big impact on plugin writers so I thought of a couple alternatives:

First, we could add a relative_path field to RepositoryContent instead of
moving it there. This would be an optional field. It would be up to plugins
to manage this field and they would still need to populate the
relative_path field on ContentArtifact. But plugins could use this optional
field to store relative paths per repository and then use this field when
generating publications.

The second alternative is one that is already laid out in the original
email but to call it out again: it would be to not solve this in pulpcore.
RPM would create its own object that would map content in a repository to
relative_paths.

David

On Tue, Apr 21, 2020 at 9:22 AM Quirin Pamp <pamp at atix.de> wrote:

> Hi,
>
>
> I am not currently very well versed in the classes involved, but moving
> relative_path around sounds slightly scary with the potential to break
> things.
>
>
> As such, I would be interested to be kept in the loop as this moves
> forward. (Mailing list once there is some movement is entirely sufficient
> 😉)
>
>
> Thanks,
>
> Quirin Pamp
> ------------------------------
> *From:* pulp-dev-bounces at redhat.com <pulp-dev-bounces at redhat.com> on
> behalf of Ina Panova <ipanova at redhat.com>
> *Sent:* 21 April 2020 14:07:13
> *To:* Daniel Alley <dalley at redhat.com>
> *Cc:* Pulp-dev <pulp-dev at redhat.com>
> *Subject:* Re: [Pulp-dev] the "relative path" problem
>
> Daniel,
>
> how about setting up a meeting and brainstorm the alternatives, pros/cons
> there?
>
>
> --------
> Regards,
>
> Ina Panova
> Senior Software Engineer| Pulp| Red Hat Inc.
>
> "Do not go where the path may lead,
>  go instead where there is no path and leave a trail."
>
>
> On Fri, Apr 17, 2020 at 5:57 PM Daniel Alley <dalley at redhat.com> wrote:
>
> Bump, this item needs to move forwards soon.  Does anyone have any
> thoughts?
>
> On Wed, Apr 1, 2020 at 9:40 AM Pavel Picka <ppicka at redhat.com> wrote:
>
> Hi,
> I'd like to add one more question to this topic. Do you think it is a
> blocker for PRs [0] & [1] as by testing [2] this features I haven't run
> into real world example where two really same name packages appears.
> I think this is a 'must have' feature but until we solve/decide it we can
> have two features working may with warning in docs for users that can
> happen in some 'special' repositories.
>
> To follow topic directly I like proposed move to 'RepositoryContent' and
> add it to its uniqueness constraint (if I understand well).
>
> [0] https://github.com/pulp/pulp_rpm/pull/1657
> [1] https://github.com/pulp/pulp_rpm/pull/1642
> [2] tested with centos 7, 8, opensuse and SLE repositories
>
> On Wed, Apr 1, 2020 at 3:22 PM Daniel Alley <dalley at redhat.com> wrote:
>
> We'd like to start a discussion on the "relative path problem" identified
> recently.
> Problem:
>
> Currently, a relative_path is tied to content in Pulp. This means that if
> a content unit exists in two places within a repository or across
> repositories, it has to be stored as two separate content units. This
> creates redundant data and potential confusion for users.
>
> As a specific example, we need to support mirroring content in pulp_rpm
> <https://pulp.plan.io/issues/6353>. Currently, for each location at which
> a single package is stored, we’ll need to create a content unit. We could
> end up with several records representing a single package. Users may be
> confused about why they see multiple records for a package and they may
> have trouble for example deciding which content unit to copy.
> Proposed Solution:
>
> Move “relative_path” from its current location on ContentArtifact, to
> RepositoryContent. This will require a sizable data migration. It is
> possibly the case that in rare cases, repository versions may change
> slightly due to deduplication.
>
> A repository-version-wide uniqueness constraint will be present on
> “relative_path”, independently of any other repository uniquness
> constraints (repo_key_fields) defined by the plugin writer.
>
> Modify the Stages API so that the relative_path can be processed in the
> correct location – instead of “DeclarativeArtifact” it will likely need to
> go on “DeclarativeContent”
>
> Remove “location_href” from the RPM Package content model – it was never a
> true part of the RPM (file) metadata, it is derived from the repository
> metadata. So storing it as a part of the Content unit doesn’t entirely make
> sense.
> Alternatives
>
> In most cases, a content unit will have a single relative path for a
> content unit. Creating a general solution to solve a one-off problem is
> usually not a good idea. As an alternative, we could look at another
> solution for mirroring content. One example might be to create a new object
> (e.g. RpmRepoMirrorContentMapping) that maps content to specific paths
> within a repo or repo version.
> Questions
>
>    - How do we handle this in pulp_file? How are content units identified
>    in pulp_file without relative_path?
>       - Checksum?
>       - How was this problem handled in Pulp 2?
>
>
> Please weigh in if you have any input on potential problems with the
> proposal, potential alternate solutions, or other insights or questions!
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>
>
>
> --
> Pavel Picka
> Red Hat
>
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