Viewsets

Each Django Rest Framework Viewset is a collection of views that provides create, update, retrieve, list, and delete, which coresponds to http POST, PATCH, GET, GET, DELETE, respectively. Some base classes will not include all of the views if they are inappropriate. For instance, the ContentViewset does not include update because Content Units are immutable in Pulp 3 (to support Repository Versions).

Most Plugins will implement:
  • viewset(s) for plugin specific content type(s), should be subclassed from ContentViewSet, ReadOnlyContentViewSet or SingleArtifactContentUploadViewSet

  • viewset(s) for plugin specific remote(s), should be subclassed from RemoteViewSet

  • viewset(s) for plugin specific publisher(s), should be subclassed from PublisherViewSet

Endpoint Namespacing

Automatically, each “Detail” class is namespaced by the app_label set in the PulpPluginAppConfig (this is set by the plugin_template).

For example, a ContentViewSet for app_label “foobar” like this:

class PackageViewSet(ContentViewSet):
    endpoint_name = 'packages'

The above example will create set of CRUD endpoints for Packages at pulp/api/v3/content/foobar/packages/ and pulp/api/v3/content/foobar/packages/<int>/

Detail Routes (Extra Endpoints)

In addition to the CRUD endpoints, a Viewset can also add a custom endpoint. For example:

class PackageViewSet(ContentViewSet):
    endpoint_name = 'packages'

    @decorators.detail_route(methods=('get',))
    def hello(self, request):
        return Response("Hey!")

The above example will create a simple nested endpoint at pulp/api/v3/content/foobar/packages/hello/

Kick off Tasks

Some endpoints may need to deploy tasks to the tasking system. The following is an example of how this is accomplished.

See dispatch for more details.

# We recommend using POST for any endpoints that kick off task.
@detail_route(methods=('post',), serializer_class=RepositorySyncURLSerializer)
# `pk` is a part of the URL
def sync(self, request, pk):
    """
    Synchronizes a repository.
    The ``repository`` field has to be provided.
    """
    remote = self.get_object()
    serializer = RepositorySyncURLSerializer(data=request.data, context={'request': request})
    # This is how non-crud validation is accomplished
    serializer.is_valid(raise_exception=True)
    repository = serializer.validated_data.get('repository')
    mirror = serializer.validated_data.get('mirror', False)

    # This is how tasks are kicked off.
    result = dispatch(
        tasks.synchronize,
        [repository, remote],
        kwargs={
            'remote_pk': remote.pk,
            'repository_pk': repository.pk,
            'mirror': mirror
        }
    )
    # Since tasks are asynchronous, we return a 202
    return OperationPostponedResponse(result, request)

If a “task_group” is provided as an optional keyword argument, then the deployed task will be automatically added to the task group. Once done spawning new tasks for a given task group, you should call .finish() on the task group object.

For more details about the reservation system and task groups, see Tasks. and TaskGroup.

Content Upload ViewSet

For single file content types, there is the special SingleArtifactContentUploadViewSet to derive from, that allows file uploads in the create method, instead of referencing an existing Artifact. Also it allows to specify a Repository, to create a new RepositoryVersion containing the newly created content. Content creation is then offloaded into a task. To use that ViewSet, the serializer for the content type should inherit from SingleArtifactContentUploadSerializer. By overwriting the deferred_validate method instead of validate, this serializer can do detailed analysis of the given or uploaded Artifact in order to fill database fields of the content type like “name”, “version”, etc. This part of validation is only called in the task context.

If the uploaded content does not need to be stored, plugin writers may derive from the class NoArtifactContentUploadViewSet. Again, the same analogy applies to this workflow. To use this ViewSet, the associated serializer should also subclass NoArtifactContentUploadSerializer. Note that by using the aforesaid Serializer and ViewSet, Pulp still loads content of an uploaded file to a temporary file. But the file is going to be removed by the end of a created task.

If any additional context needs to be passed from the ViewSet to the creation task, the get_deferred_context method of the ViewSet might be overwritten. It’s return value will then be available as self.context in the Serializer.

Note

Context passed from the ViewSet to the Task must be easily serializable. i.e. one cannot return the request from get_deferred_context.