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

Tue Oct 31 19:55:48 UTC 2017

On Tue, Oct 31, 2017 at 3:52 PM, Brian Bouterse <bbouters at redhat.com> wrote:

> 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?
>
>
Yes, the response would the same as it for the /publish URL right now. This
is just a change in the URL that is used to make the request.

> 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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