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

Tue Oct 31 19:52:48 UTC 2017

Would that return the 202 w/ a link to the task because the publication
hasn't been created yet? Then using the created_resources they can see what
was created, and in the event of failure the task fails and there are no
created_resources.

@dkliban is ^ the idea?

On Tue, Oct 31, 2017 at 3:48 PM, Dennis Kliban <dkliban at redhat.com> wrote:

>
>
> 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
>>>>>>
>>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> Pulp-dev mailing list
>>>>> Pulp-dev at redhat.com
>>>>> https://www.redhat.com/mailman/listinfo/pulp-dev
>>>>>
>>>>>
>>>>
>>>
>>
>
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