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. David On Wed, Oct 25, 2017 at 11:03 AM, Brian Bouterse <[email protected]> wrote: > > > On Tue, Oct 24, 2017 at 10:00 PM, Michael Hrivnak <[email protected]> > wrote: > >> >> >> On Tue, Oct 24, 2017 at 2:11 PM, Brian Bouterse <[email protected]> >> 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 > [email protected] > https://www.redhat.com/mailman/listinfo/pulp-dev > >
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