[Pulp-dev] [pulp 3] proposed change to publishing REST api

Tue Oct 31 19:48:54 UTC 2017

On Tue, Oct 31, 2017 at 3:40 PM, Brian Bouterse <bbouters at redhat.com> wrote:

> +1 to updating #3033 to have a created_resources attribute which would be
> a list of GenericForeignKeys. It also needs docs, but I'm not entirely sure
> where.
>
> If we're going to introduce the above attribute, I think having the
> controller endpoint as-is would be the most usable. @dkliban do you see
> value in changing the URL structure if the created_resources attribute is
> introduced?
>
>
This API call creates a publication resource. A POST to
publishers/<id>/publications/ seems most appropriate for creating new
publication resources.

I can help review/groom these if that is helpful.
>
> -Brian
>
>
> On Tue, Oct 31, 2017 at 1:39 PM, David Davis <daviddavis at redhat.com>
> wrote:
>
>> Personally I am not opposed to the url endpoint you suggest.
>>
>> It also seems like there is some consensus around adding a ‘created
>> resources’ relationship to Task or at least prototyping that out to see
>> what it would look like.
>>
>> If no one disagrees, should I update issue #3033 with those two items?
>>
>>
>> David
>>
>> On Wed, Oct 25, 2017 at 1:23 PM, Dennis Kliban <dkliban at redhat.com>
>> wrote:
>>
>>> On Wed, Oct 25, 2017 at 11:24 AM, David Davis <daviddavis at redhat.com>
>>> wrote:
>>>
>>>> I don’t know that the ambiguity around whether a task has a publication
>>>> or not is a big deal. If I call the publication endpoint, I’d expect a
>>>> publication task which either has 1 publication or 0 (if the publication
>>>> failed) attached to it.
>>>>
>>>> In terms of ambiguity, I see a worse problem around adding a task_id
>>>> field to publications. As a user, I don’t know if a publication failed or
>>>> not when I get back a publication object. Instead, I have to look up the
>>>> task to see if it is a real (or successful) publication. Moreover, since we
>>>> allow users to remove/clean up tasks, that task may not even exist anymore.
>>>>
>>>>
>>> I agree that the ephemeral nature of tasks makes the originally proposed
>>> solution non-deterministic. I am open to associating 'resources created'
>>> with a task instead.
>>>
>>> However, I still think there is value in changing the rest API endpoint
>>> for starting a publish task to POST /api/v3/repositories/<repo-id>
>>> /publishers/<type>/<name>/publications/. However, I will start a
>>> separate thread for that discussion.
>>>
>>>  - Dennis
>>>
>>>
>>>>
>>>> David
>>>>
>>>> On Wed, Oct 25, 2017 at 11:03 AM, Brian Bouterse <bbouters at redhat.com>
>>>> wrote:
>>>>
>>>>>
>>>>>
>>>>> On Tue, Oct 24, 2017 at 10:00 PM, Michael Hrivnak <mhrivnak at redhat.com
>>>>> > wrote:
>>>>>
>>>>>>
>>>>>>
>>>>>> On Tue, Oct 24, 2017 at 2:11 PM, Brian Bouterse <bbouters at redhat.com>
>>>>>> wrote:
>>>>>>
>>>>>>> Thanks everyone for all the discussion! I'll try to recap the
>>>>>>> problem and some of the solutions I've heard. I'll also share some of my
>>>>>>> perspective on them too.
>>>>>>>
>>>>>>> What problem are we solving?
>>>>>>> When a user calls "publish" (the action API endpoint) they get a 202
>>>>>>> w/ a link to the task. That task will produce a publication. How can the
>>>>>>> user find the publication that was produced by the task? How can the user
>>>>>>> be sure the publication is fully complete?
>>>>>>>
>>>>>>>
>>>>>>> What are our options?
>>>>>>> 1) Start linking to created objects from task status. I believe its
>>>>>>> been clearly stated about why we can't do this. If it's not clear, or if
>>>>>>> there are other things we should consider, let's talk about it.
>>>>>>> Acknowledging or establishing agreement on this is crucial because a change
>>>>>>> like this would bring back a lot of the user pain from pulp2. I believe the
>>>>>>> HAL suggestion falls into this area.
>>>>>>>
>>>>>>
>>>>>> I may have missed something, but I do not think this is clear. I know
>>>>>> that Pulp 2's API included a lot of unstructured data, but that is not at
>>>>>> all what I'm suggesting here.
>>>>>>
>>>>>> It is standard and recommended practice for REST API responses to
>>>>>> include links to resources along with information about what type of
>>>>>> resource each link references. We could include a reference to the created
>>>>>> resource and an identifier for what type of resource it is, and that would
>>>>>> be well within the bounds of good REST API design. HAL is just one of
>>>>>> several ways to accomplish that, and I'm not pitching any particular
>>>>>> solution there. In any case, I'm not sure what the problem would be with
>>>>>> this approach.
>>>>>>
>>>>>
>>>>> I agree it is a standard practice for a resource to include links to
>>>>> other resources, but the proposal is to include "generic" links is
>>>>> different and creates a different user experience. I believe referencing
>>>>> the task from the publication will be easier for users and clients. When a
>>>>> user looks up a publication, they will always know they'll get between 0
>>>>> and 1 links to a task. You can use that to check the state of the
>>>>> publication. If we link to "generic" resources (like a publication) from a
>>>>> task, then if I ask a user "do you expect task
>>>>> ede3af3e-d5cf-4e18-8c57-69ac4d4e4de6 to contain a link to a
>>>>> publication or not?" you can't know until you query it. I think that
>>>>> ambiguity was a pain point in Pulp2. I don't totally reject this solution,
>>>>> but this is an undesirable property (I think).
>>>>>
>>>>>
>>>>>>
>>>>>>>
>>>>>>> 2) Have the user find the publication via query that sorts on time
>>>>>>> and filters only for a specific publisher. This could be fragile because
>>>>>>> with a multi-user system and no hard references between publications and
>>>>>>> tasks, answering the question "which is the publication for me" is hard
>>>>>>> because another user could have submitted a publish too. While not totally
>>>>>>> perfect, this could work.
>>>>>>>
>>>>>>
>>>>>> In theory if a user queried for a publication from a specific
>>>>>> publisher that was created between the start and end times of the task,
>>>>>> that should unambiguously identify the correct publication. But depending
>>>>>> on timestamps is not a particularly robust nor confidence-inspiring way to
>>>>>> reference a resource.
>>>>>>
>>>>> Agreed and Agreed
>>>>>
>>>>>
>>>>>>
>>>>>>>
>>>>>>> 3) Have the user create a publication directly like any other REST
>>>>>>> resource, and help the user understand the state of that resource over
>>>>>>> time. I believe the proposal at the start of this thread is recommending
>>>>>>> this solution. I'm also +1 on this solution.
>>>>>>>
>>>>>>
>>>>>> I think the problem with this is that a user cannot create a
>>>>>> publication. A user can only ask a plugin to create a publication. Until
>>>>>> the plugin creates the publication, there is no publication.
>>>>>>
>>>>>
>>>>> Note a publication is an object, but really we mean a publication and
>>>>> it's related PublishedArtifact, PublishedMetadat, etc objects. It would be
>>>>> straightforward for a user to create a publication using the viewset and
>>>>> have the task associated with it call the publisher to build out the
>>>>> associated PublishedArtifact, PublishedContent, PublishedMetadata, etc. We
>>>>> should explore if this is good or not, but it is possible.
>>>>>
>>>>> As an aside, this is related to a problem everyone should be aware of:
>>>>> the existence of a publication does not guarantee that publication is
>>>>> finished publishing. Even with option 1, where the task creates the
>>>>> publisher and links to it in the task status, while the publisher is
>>>>> running it must save the Publication so that the PublishedArtifact, etc can
>>>>> link to it. So for any given publication, in order to know if it's "fully
>>>>> finished and consistent" you must be able to check the status of the
>>>>> associated task that produced it.
>>>>>
>>>>>
>>>>>>
>>>>>>> As an aside, I don't think considering versioned repos as a possible
>>>>>>> solution is helping us with this problem. The scope of the current problem
>>>>>>> is relatively small and the scope of planning for versioned repos is large.
>>>>>>>
>>>>>>>
>>>>>> Versioned repos is a potential solution. In that scenario, a user
>>>>>> would request publication of a specific repo version (perhaps defaulting to
>>>>>> the latest), the publication would be linked to that version, and that is
>>>>>> an easy mechanism for the user to find the publication they want.
>>>>>> Ultimately the user is interested in working with a specific content set
>>>>>> anyway. They get a repo to a state where it has the content they want, and
>>>>>> then they publish that content set. No matter what we do with publications,
>>>>>> users will think of them in terms of related content sets. A repo version
>>>>>> is that immutable content set they can work with confidently.
>>>>>>
>>>>>
>>>>> It's neat to me that that versions are snapshots of content and
>>>>> publications are snapshots of content. Publications already create much of
>>>>> the value propostion of versioned repos with publications. They allow you
>>>>> to work with specific content sets like you describe. Also they allow for
>>>>> rollback. So that is all great for our users. For this thread, I want to
>>>>> bring the conversation back to where it started, solving a small problem
>>>>> about linking two resources that already exist.
>>>>>
>>>>>
>>>>>> It helps the rollback scenario a lot as well. Versioning repos allows
>>>>>> a user to see what the differences are between two content sets, and thus
>>>>>> two different publications, which informs them about when and how far back
>>>>>> they should roll back a distribution.
>>>>>>
>>>>>
>>>>>> - user discovers a horrible flaw in a piece of content
>>>>>> - user queries for which version of the repo introduced that piece of
>>>>>> content
>>>>>> - user updates the distribution to serve the publication that came
>>>>>> before the one which introduced the piece of content, optionally
>>>>>> re-publishing that version in case its publication was deleted or had never
>>>>>> been made in the first place.
>>>>>>
>>>>>> --
>>>>>>
>>>>>> Michael Hrivnak
>>>>>>
>>>>>> Principal Software Engineer, RHCE
>>>>>>
>>>>>> Red Hat
>>>>>>
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> Pulp-dev mailing list
>>>>> Pulp-dev at redhat.com
>>>>> https://www.redhat.com/mailman/listinfo/pulp-dev
>>>>>
>>>>>
>>>>
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>>>>
>>>>
>>>
>>
>
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