This is the plugin_template repository to help plugin writers get started and write their own plugin for Pulp Project 3.0+.

Plugin Writing Walkthrough

If you are planning on writing a new Pulp plugin, but have no idea what you're doing you've come to the right place. The purpose of this guide is to walk you through, step by step, the Pulp plugin creation process.

This guide specifically details how you write a new content plugin.

Why would you want to write a plugin?

What exactly is this Pulp thing?

It's recommend that you develop on a system that already has Pulp installed. This allows you to test your plugin at every step.

It's also recommended that you go through the planning guide before starting to develop your plugin.

Generate a plugin template config for a new Pulp plugin

The first step is to create a template_config.yml for your new plugin. This file contains settings used by the ./plugin-template command when generating new plugins and for future updates.

The first time this file is generated. bootstrap this template. This will create a functional but useless plugin, with minimal code, docs, tests, and default Travis CI configuration. Later on we'll discuss exactly what each part of this template does and what to change to create a 'real' plugin.

1. Clone this repository

   $ git clone https://github.com/pulp/plugin_template.git

   $ cd plugin_template

2. Run the provided ./plugin-template --generate-config

   $ ./plugin-template --generate-config --plugin-app-label <label> PLUGIN_NAME

   NOTE : The plugin-app-label should identify the content type which you would like to support, e.g. rubygem or maven. The PLUGIN_NAME is usually pulp_ or pulp- prepended to the --plugin-app-label, e.g. pulp_maven.

The first time this command is run, a new directory by the name of PLUGIN_NAME is created inside the parent directory of the plugin_template' directory. The template_config.yml` is written to the root of this new directory. Subsequent uses of the command simply update that file.

The following settings are stored in template_config.yml.

  pypi-username         The username that should be used when uploading packages to PyPI. It
                        is required unless deploy-client-to-pypi and deploy-daily-client-to-pypi
                        and deploy-to-pypi are specified.

  docs-test             Include a Travis build for testing the 'make html' command for sphinx docs.

  deploy-to-pypi        Include a Travis stage that publishes builds to PyPI

                        This stage only executes when a tag is associated with the commit being
                        built. When enabling this stage, the user is expected to provide a
                        secure environment variable called PYPI_PASSWORD. The variable can
                        be added in the travis-ci.com settings page for the project[0]. The PYPI
                        username is specified using --pypi-username option.

  test-bindings         Include a Travis stage that runs a script to test generated client
                        library.

                        This stage requires the plugin author to include a 'test_bindings.py'
                        script in the .travis directory of the plugin repository. This script
                        is supposed to exercise the generated client library.

  deploy-client-to-pypi Include a Travis stage that publishes a client library to PyPI.

                        This stage only executes when a tag is associated with the commit being
                        built. When enabling this stage, the user is expected to provide a
                        secure environment variable called PYPI_PASSWORD. The variable can
                        be added in the travis-ci.com settings page for the project[0]. The PYPI
                        username is specified using --pypi-username option.

                        This stage uses the OpenAPI schema for the plugin to generate a Python
                        client library using openapi-generator-cli.

  deploy-client-to-rubygems
                        Include a Travis stage that publishes a client library to RubyGems.org.

                        This stage only executes when a tag is associated with the commit being
                        built. When enabling this stage, the user is expected to provide a
                        secure environment variable called RUBYGEMS_API_KEY. The variable can
                        be added in the travis-ci.com settings page for the project.

  deploy-daily-client-to-pypi
                        Include a Travis stage that publishes a client library to PyPI.

                        This stage only executes when a tag is associated with the commit being
                        built. When enabling this stage, the user is expected to provide a
                        secure environment variable called PYPI_PASSWORD. The variable can
                        be added in the travis-ci.com settings page for the project[0]. The PYPI
                        username is specified using --pypi-username option.

                        This stage uses the OpenAPI schema for the plugin to generate a Python
                        client library using openapi-generator-cli.

                        [0] https://docs.travis-ci.com/user/environment-variables/
                        #defining-variables-in-repository-settings

  deploy-daily-client-to-rubygems
                        Include a Travis stage that publishes a client library to RubyGems.org
                        with each CRON build.

                        This stage only executes on builds trigerred by CRON. When enabling
                        this stage, the user is expected to provide a secure environment
                        variable called RUBYGEMS_API_KEY. The variable can be added in the
                        travis-ci.com settings page for the project.

  check-commit-message  Include inspection of commit message for a reference to an issue in
                        pulp.plan.io.

  coverage              Include collection of coverage and reporting to coveralls.io

  travis-notifications  A yaml block that contains configuration for Travis build notifications. See
                        https://docs.travis-ci.com/user/notifications/ for configuration options.

Bootstrap a new Pulp plugin

The next step is to bootstrap the plugin. This will create a functional but useless plugin, with minimal code and tests.

1. Run the plugin-template --bootstrap command. This will create a skeleton for your plugin. It will contain a setup.py, expected plugin layout and stubs for necessary classes, methods, and tests.

   $ ./plugin-template --bootstrap PLUGIN_NAME

In addition to the basic plugin boilerplate, this template also provides a basic set of functional tests using the pulp_smash framework.

In order to use these tests, you will need to address the "FIXME" messages left in places where plugin-writer intervention is required.

Add Travis CI configuration to a Pulp plugin

The next step is to add a Travis configuration file and scripts for continuous integration. These are highly recommended, as they will make continuous verification of your plugin's functionality much easier.

1. Run the ./plugin-template --travis command to generate the Travis CI config based on the settings in template_config.yml.

   $ ./plugin-template --travis PLUGIN_NAME

Running the command again will update the plugin with the latest Travis CI configuration provided by the plugin-template.

Add Documentation to a Pulp plugin

The next step is to add documentation that can be hosted on Read the Docs.

1. Run the ./plugin-template --docs command to generate the docs.

   $ ./plugin-template --docs PLUGIN_NAME

Discoverability

After bootstrapping, your plugin should be installable and discoverable by Pulp.

1. Install your bootstrapped plugin

   pip install -e your_plugin_name

2. Start/restart the Pulp Server

   django-admin runserver 24817

3. Check that everything worked and you have a remote endpoint

   $ http GET http://localhost:24817/pulp/api/v3/remotes/{{ plugin_app_label }}/{{ plugin_dash_short }}/

The plugin specific /pulp/api/v3/publishers/{{ plugin_dash_short }}/ and /pulp/api/v3/content/{{ plugin_dash_short }}/ endpoints should now also be available, and you can validate this by checking the hosted docs http://localhost:24817/pulp/api/v3/docs

Your plugin is discoverable by Pulp because it is [a Django application that subclasses pulpcore.plugin.PulpPluginAppConfig]({{ plugin_snake }}/app/init.py)

For more information about plugin discoverability, including how it works and plugin entrypoints see the discoverability documentation

Customizing Plugin Behavior

First, look at the overview of Pulp Models to understand how Pulp fits these pieces together.

Bootstrapping created three new endpoints (remote, publisher, and content). Additional information should be added to these to tell Pulp how to handle your content.

For each of these three endpoints, the bootstrap has created a model, a serializer and a viewset. The model is how the data is stored in the database. The serializer converts complex data to easily parsable types (XML, JSON). The viewset provides the handlers to serve/receive the serialized data.

Subclassing Content, Remote, Publisher

Always subclass the relevant model, serializer, and viewset from the pulpcore.plugin namespace. Pulp provides custom behavior for these, and although implementation details are located in pulpcore.app, plugins should always use pulpcore.plugin instead, since pulpcore.plugin gurantees the plugin API semantic versioning

Models:

• model(s) for the specific content type(s) used in plugin, should be subclassed from pulpcore.plugin.models.Content model
• model(s) for the plugin specific remote(s), should be subclassed from pulpcore.plugin.models.Remote model
• model(s) for the plugin specific publisher(s), should be subclassed from pulpcore.plugin.models.Publisher model

Serializers:

• serializer(s) for plugin specific content type(s), should be subclassed from pulpcore.plugin.serializers.ContentSerializer
• serializer(s) for plugin specific remote(s), should be subclassed from pulpcore.plugin.serializers.RemoteSerializer
• serializer(s) for plugin specific publisher(s), should be subclassed from pulpcore.plugin.serializers.PublisherSerializer

Viewsets:

• viewset(s) for plugin specific content type(s), should be subclassed from pulpcore.plugin.viewsets.ContentViewSet
• viewset(s) for plugin specific remote(s), should be subclassed from pulpcore.plugin.viewsets.RemoteViewset
• viewset(s) for plugin specific publisher(s), should be subclassed from pulpcore.plugin.viewsets.PublisherViewset

Keep namespacing in mind when writing your viewsets.

Content

Model

First model your content type. This file is located at [{{ plugin_snake }}/app/models.py]({{ plugin_snake }}/app/models.py). Add any fields that correspond to the metadata of your content, the could be the project name, the author name, or any other type of metadata.

The TYPE class attribute is used for filtering purposes. If a uniqueness constraint is needed, add a Meta class to the model like so:

class {{ plugin_camel_short }}Content(Content):
    TYPE = '{{ plugin_dash_short }}'
    filename = models.TextField(unique=True, db_index=True, blank=False)

    class Meta:
        unique_together = ('filename',)

After adding the model, you can run the migration with

pulp-manager makemigrations {{ plugin_app_label }}

And make sure all your fields are on the {{ plugin_app_label }} database table.

Serializer

Next, add a corresponding serializer field on the in [{{ plugin_snake }}/app/serializers.py]({{ plugin_snake }}/app/serializers.py). See the DRF documentation on serializer fields to see what's available

Viewset

Last, add any additional routes to your [{{ plugin_snake }}/app/viewsets.py]({{ plugin_snake }}/app/viewsets.py). The content viewset usually doesn't require any additinal routes, so you can leave this alone for now.

Remote

A remote knows specifics of the plugin Content to put it into Pulp. Remote defines how to synchronize remote content. Pulp Platform provides support for concurrent downloading of remote content. Plugin writer is encouraged to use one of them but is not required to.

Model

First model your remote. This file is located at [{{ plugin_snake }}/app/models.py]({{ plugin_snake }}/app/models.py). Add any fields that correspond to the remote source.

Remember to define the TYPE class attribute which is used for filtering purposes,

Serializer

Next, add a corresponding serializer field on the in [{{ plugin_snake }}/app/serializers.py]({{ plugin_snake }}/app/serializers.py).

Viewset

Last, add any additional routes to your [{{ plugin_snake }}/app/viewsets.py]({{ plugin_snake }}/app/viewsets.py). Note the sync route is predefined for you. This route kicks off a task [{{ plugin_snake }}.app.tasks.synchronizing.py]({{ plugin_snake }}.app.tasks.synchronizing.py).

Publisher

Model

e. This file is located at [{{ plugin_snake }}/app/models.py]({{ plugin_snake }}/app/models.py). Add any additional fields.

Make sure you define the TYPE class attribute which is used for filtering purposes,

Serializer

Next, add a corresponding serializer field on the in [{{ plugin_snake }}/app/serializers.py]({{ plugin_snake }}/app/serializers.py).

Viewset

Last, add any additional routes to your [{{ plugin_snake }}/app/viewsets.py]({{ plugin_snake }}/app/viewsets.py). Note the publish route is predefined for you. This route kicks off a task [{{ plugin_snake }}.app.tasks.publishing.py]({{ plugin_snake }}.app.tasks.publishing.py).

Exporter

TODO

Tasks

Tasks such as sync and publish are needed to tell Pulp how to perform certain actions.

More about Sync task

More about Publish task

More about Export task

Tests

TODO

Documentation

Your bootstrap template comes with a set of prepopulated docs. You can host these on readthedocs when you are ready.

Pulp also comes with a set of auto API docs. When your plugin is installed endpoints in the live api docs will be automatically populate.

When you run 'make html' command to build the docs, you must have the pulp-api running on localhost. The 'make html' command first downloads the OpenAPI schema for the plugin and saves it in docs/_static/api.json. You should add this file to git. This file will then provide data needed to display the restapi.html page in the root of the built docs.

Travis configuration

This repository also provides a script for generating a Travis configuration. The script should be run with the following command.

$ ./plugin-template --travis plugin_name plugin_app_label

The default behavior enables two build stages that generate client libraries using the OpenAPI schema. One publishes to PyPI using pypi-username setting and the secret environment variable called $PYPI_PASSWORD. The other stage publishes the client to rubygems.org and requires the $RUBYGEMS_API_KEY environment variable to be set. Both environment variables can be created on the travis-ci.com settings page for the plugin[0]. The stage that publishes tagged builds to PyPI uses the same configs as the client publishing stage. The default pipeline can be created using the following commands:

$ git clone git@github.com/pulp/{{ plugin_app_label }}
$ cd {{ plugin_app_label }}
$ # copying the requirements file is only needed if plugin was created before this file was added
$ # to the plugin template
$ cp doc_requirements.txt ../pulp_<plugin_name>/
$ touch ../pulp_<plugin_name>/.travis/test_bindings.py
$ ./plugin-template --travis --pypi-username your_pypi_username plugin_name

The before_install.sh, install.sh, before_script.sh, and script.sh can be augmented by plugin writers by creating specially named scripts in their .travis directories. The scripts are executed in the following order, with optional plugin provided scripts in bold:

1. pre_before_install.sh
2. before_install.sh
3. post_before_install.sh
4. install.sh
5. pre_before_script.sh
6. before_script.sh
7. post_before_script.sh
8. script.sh
9. post_docs_test.sh
10. post_script.sh

The pipeline can be modified, see the help text for available options.

$ ./plugin-template --help
usage: plugin-template [-h] [--generate-config] [--bootstrap] [--test]
                       [--travis] [--docs] [--all] [--verbose]
                       plugin_name plugin_app_label

Generate a .travis.yml and .travis directoryfor a specified plugin

positional arguments:
  plugin_name           Create or update this plugin.
  plugin_app_label      the Django app label for the plugin - usually the part after pulp_ or
                     pulp-


optional arguments:
  -h, --help            show this help message and exit
  --bootstrap           Create a new plugin and template boilerplate code.

  --test                Generate or update functional and unit tests.

  --travis              Generate or update travis configuration files.

  --docs                Generate or update plugin documentation.

  --all                 Create a new plugin and template all non-excluded files.

  --verbose             Include more output.

Additional Topics

• CLI
• Community Development
• Live API
• Error Handling
• Releasing

A Plugin Completeness Checklist

• Plugin django app is defined using PulpAppConfig as a parent

• Plugin entry point is defined

• pulpcore-plugin is specified as a requirement in setup.py

• Necessary models/serializers/viewsets are defined. At a minimum:

  • models for plugin content type, remote, publisher
  • serializers for plugin content type, remote, publisher
  • viewset for plugin content type, remote, publisher

• Errors are handled according to Pulp conventions

• Docs for plugin are available (any location and format preferred and provided by plugin writer)

{{ plugin_dash }}

A Pulp plugin to support hosting your own {{ plugin_dash_short }}.

For more information, please see the documentation or the Pulp project page.