[Pulp-dev] Pulp 3 REST API Challenges

Thu Apr 12 21:49:36 UTC 2018

On Thu, Apr 12, 2018 at 2:49 PM, Jeff Ortel <jortel at redhat.com> wrote:

>
>
> On 04/11/2018 01:13 PM, Dennis Kliban wrote:
>
> On Tue, Apr 10, 2018 at 6:44 PM, Jeff Ortel <jortel at redhat.com> wrote:
>
>>
>>
>> On 04/10/2018 04:15 PM, Dennis Kliban wrote:
>>
>> On Tue, Apr 10, 2018 at 2:04 PM, Brian Bouterse <bbouters at redhat.com>
>> wrote:
>>
>>> These are good problem statements. I didn't understand all of the
>>> aspects of it, so I put some inline questions.
>>>
>>> My overall question is: are these related problems? To share my answer
>>> to this, I believe the first two problems are related and the third is
>>> separate. The classic divide and conquor approach we could use here is to
>>> confirm that the problems are unrelated and focus on resolving one of them
>>> first.
>>>
>>>
>> I don't think all 3 are related problems. The motivation for grouping all
>> together is that a subset of the action endpoints from problem 1 are used
>> to create repository versions and Problem 3 is a problem with the
>> repository version creation API.
>>
>>
>>>
>>> On Mon, Apr 9, 2018 at 3:18 PM, Austin Macdonald <austin at redhat.com>
>>> wrote:
>>>
>>>> Folks,
>>>>
>>>> Austin, Dennis, and Milan have identified the following issues with
>>>> current Pulp3 REST API design:
>>>>
>>>>    - Action endpoints are problematic.
>>>>    - Example POST@/importers/<plugin>/sync/
>>>>       - They are non-RESTful and would make client code tightly
>>>>       coupled with the server code.
>>>>       - These endpoints are inconsistent with the other parts of the
>>>>       REST API.
>>>>
>>>> Is self-consistency really a goal? I think it's a placeholder for
>>> consistency for REST since the "rest" of the API is RESTful. After reading
>>> parts of Roy Fielding's writeup of the definition of REST I believe "action
>>> endpoints are not RESTful" to be a true statement. Maybe "Action endpoints
>>> are problematic" should be replaced with "Action endpoints are not RESTful"
>>> perhaps and have the self-consistency bullet removed?
>>>
>>
>> +1 to "Action endpoints are not RESTful"
>> +1 to removing the self-consistency language
>>
>>
>>>
>>>>    - DRF is not being used as intended for action endpoints so we have
>>>>       to implement extra code. (against the grain)
>>>>
>>>> I don't know much about this. Where is the extra code?
>>>
>>>
>>>>
>>>>    - We don't have a convention for where plug-in-specific, custom
>>>>    repository version creation endpoints.
>>>>    - example POST@/api/v3/<where?>/docker/add/
>>>>       - needs to be discoverable through the schema
>>>>
>>>> What does discoverable via the schema ^ mean? Aren't all urls listed in
>>> the schema?
>>>
>>> I think of ^ problem somewhat differently. Yes all urls need to be
>>> discoverable (a REST property), but isn't it more of an issue that the urls
>>> which produce repo versions can't be identified distinctly from any other
>>> plugin-contributed url? To paraphrase this perspective: making a repo
>>> version is strewn about throughout the API in random places which is a bad
>>> user experience. Is that what is motivation url discovery?
>>>
>>>
>>
>> Yes. I envision a CLI that can discover new plugin
>> repository-version-creating functionality without having to install new
>> client packages. Allowing plugin writers to add endpoints in arbitrary
>> places for creating repository versions will make it impossible for the
>> client to know what all the possible ways of creating a repository version
>> are.
>>
>>
>>>
>>>>    - For direct repository version creation, plugins are not involved.
>>>>    - validation correctness problem: https://pulp.plan.io/issues/3541
>>>>       - example: POST@/api/v3/repositories/<repository_id>/versions/
>>>>
>>>> I agree with this problem statement. In terms of scope it affects some
>>> plugin writers but not all.
>>>
>>
>> I think it affects all plugin writers. Even the File plugin needs to
>> provide some validation when creating a repository version. Right now you
>> can add a FileContent with the same relative path as another FileContent in
>> the repository version. This should not be possible because it's not a
>> valid combination of FileContent units in the same repository version.
>>
>>
>> Not necessarily.  Two files with the same relative path will have
>> different digest (different content).  The assumption that they both cannot
>> be in the same repository makes assumptions about how the repository is
>> used which I don't think is a good idea.  Image two different versions of
>> abc.iso.
>>
>>
> Why is it bad to assume that a repository version is going to be
> published? What are the other ways to use a repository version?
>
>
> The repository may not be publish and/or may not be published by the
> FilePublisher in the file plugin project.  A user may want to sync and
> store many version of an iso in the repository and then selectively *add*
> a specific version to another repository for promotion work flows.  Also,
> the user could use another (custom) publisher that deals differently with
> multiple files with the same path in the repository.  The FilePublisher
> currently publishes the newest.  My point being, we, really cannot assume
> how the repository will be used or which publisher *may* publish it.
>
>
The problem was initially stated as "For direct repository version
creation, plugins are not involved". It sounds like you disagree that this
is a problem. Can you confirm this by telling us if plugins should be able
to provide validation for this API provided by core?

>
> A File repository version cannot be properly published if it contains 2
> FileContent units that both have the same relative path. The publisher has
> to decide which FileContent to publish at the relative path. That decision
> cannot be made intelligently by the publisher. The decision on which
> content unit to include in the repository version rests with the user that
> is creating the repository version. When a user tries to create a
> repository version with a FileContent that has the same relative path as
> another FileContent that was added previously, Pulp needs to inform the
> user that there is a conflict (and not create the repositiory version).
> This validation can only be provided by the File plugin.
>
>
>>
>>
>>>
>>>
>>>> We would like to get feedback on these issues being sound and worth
>>>> resolving before we resume particular solution discussion[1].
>>>>
>>>> Thanks,
>>>> Austin, Dennis, and Milan
>>>>
>>>> [1] https://www.redhat.com/archives/pulp-dev/2018-March/msg00066.html
>>>>
>>>>
>>>> _______________________________________________
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>>>>
>>>>
>>>
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>>>
>>
>>
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