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

Brian Bouterse bbouters at redhat.com
Mon Oct 23 15:43:39 UTC 2017

There is a lot of good discussion here. See inline about the motivation to
not add additional fields to the task model.

On Mon, Oct 23, 2017 at 10:55 AM, Michael Hrivnak <mhrivnak at redhat.com>

> Unless the publication can be created before the response is returned, the
> response code will need to still be 202.
> As for the path, either way seems workable, although I have two
> hesitations about POSTing to publications/.
> 1) Normally in REST when a user creates a resource via POST to a
> collection endpoint, they are expected to provide a representation of the
> new resource, even if it is only partial. In the case of initiating a
> publish task, we do not want the user to provide any part of the new
> publication's state. We only want the user to optionally provide a bit of
> information about *how* to create a new publication. Should the publication
> be incremental or not? Which repo version should be published? etc. The
> difference may seem subtle, but I think it's important.
> 2) The act of creating a publication may also change state of other
> resources, and not only subordinate resources such as a publication
> artifact. For example, if there is a Distribution with auto_update set to
> True, its state will be changed by a publish task. That could be seen as an
> unexpected side effect when merely POSTing to a publications/ endpoint.
> When an operation affects state across multiple resources and resource
> types, that's usually a good time to use a "controller" type endpoint that
> is specific to the operation.
> Our asynchronous tasks will often need to create one or more resources. A
> publish task creates a publication. An upload-related task may create one
> or more content units. A sync/associate/unassociate task will create a new
> repository version. New resources are the output of those tasks. However
> each of those tasks will sometimes not create any resources, such as when
> an equivalent resource already exists. Creating resources is a common
> characteristic of tasks, so it would make sense to report that in a
> standard part of the task status.
> A task status should not include an exhaustive list of every resource
> created. For example, a publish task should not include a reference to
> every metadata artifact it made. It would be sufficient to include a
> reference to the publication, the task's primary output, which then can be
> used to reference subordinate resources.
> On a task status representation, this could be included in a field called
> "created_resources", "output", "return_value", or similar.
> Thoughts on that idea?

This is similar to what we did on Pulp2 where task status field semantics
are different task by task. In other words this field's usage and data
differs depending on the task type making it like a mutating field. This
was a real challenge for users in Pulp2 because the data semantics and
format are all different which prevents users from handling that field
generically. Currently all fields on a task status are semantically
concrete. I think we should continue to do that.

> On Fri, Oct 20, 2017 at 11:27 AM, Mihai Ibanescu <mihai.ibanescu at gmail.com
> > wrote:
>> That seems sensible, and in line with REST's mantra of "nouns in resource
>> URLs, not verbs".
>> On Thu, Oct 19, 2017 at 3:27 PM, Dennis Kliban <dkliban at redhat.com>
>> wrote:
>>> @jortel and I have been discussing[0] how a user should find out what
>>> publication was created after a request is made to
>>> http://localhost:8000/api/v3/repositories/foo/publishers/exa
>>> mple/bar/publish/
>>> I propose that we get rid of the above URL from our REST API and add
>>> ability to POST to http://localhost:8000/api/v3/r
>>> epositories/foo/publishers/example/bar/publications/ instead. The
>>> response would be a 201. Each publication would have a task associated with
>>> it.
>>> This work would probably be done by whoever picks up issue 3033[1].
>>> [0] https://pulp.plan.io/issues/3035
>>> [1] https://pulp.plan.io/issues/3033
>>> _______________________________________________
>>> Pulp-dev mailing list
>>> Pulp-dev at redhat.com
>>> https://www.redhat.com/mailman/listinfo/pulp-dev
>> _______________________________________________
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> --
> Michael Hrivnak
> Principal Software Engineer, RHCE
> Red Hat
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