python-openstackclient/doc/source/contributor/plugins.rst

Plugins

The OpenStackClient plugin system is designed so that the plugin need only be properly installed for OSC to find and use it. It utilizes Python's entry points mechanism to advertise to OSC the plugin module and supported commands.

Adoption

OpenStackClient promises to provide first class support for the following OpenStack services: Compute, Identity, Image, Object Storage, Block Storage and Network (core objects). These services are considered essential to any OpenStack deployment.

Other OpenStack services, such as Orchestration or Telemetry may create an OpenStackClient plugin. The source code will not be hosted by OpenStackClient.

The following is a list of projects that are an OpenStackClient plugin.

• aodhclient
• gnocchiclient
• osc-placement
• python-barbicanclient
• python-designateclient
• python-heatclient
• python-ironicclient
• python-ironic-inspector-client
• python-mistralclient
• python-muranoclient
• python-neutronclient***
• python-octaviaclient
• python-rsdclient
• python-saharaclient
• python-senlinclient
• python-tripleoclient**
• python-troveclient
• python-watcherclient
• python-zaqarclient
• python-zunclient

** Note that some clients are not listed in global-requirements.

*** Project contains advanced network services.

The following is a list of projects that are not an OpenStackClient plugin.

• python-magnumclient
• python-monascaclient
• python-solumclient

Implementation

Client module

Plugins are discovered by enumerating the entry points found under :pyopenstack.cli.extension and initializing the specified client module.

[entry_points]
openstack.cli.extension =
    oscplugin = oscplugin.client

The client module must define the following top-level variables:

• API_NAME - A string containing the plugin API name; this is the name of the entry point declaring the plugin client module (oscplugin = ... in the example above) and the group name for the plugin commands (openstack.oscplugin.v1 = in the example below). OSC reserves the following API names: compute, identity, image, network, object_store and volume.
• API_VERSION_OPTION (optional) - If set, the name of the API version attribute; this must be a valid Python identifier and match the destination set in build_option_parser().
• API_VERSIONS - A dict mapping a version string to the client class

The client module must implement the following interface functions:

• build_option_parser(parser) - Hook to add global options to the parser
• make_client(instance) - Hook to create the client object

OSC enumerates the plugin commands from the entry points in the usual manner defined for the API version:

openstack.oscplugin.v1 =
    plugin_list = oscplugin.v1.plugin:ListPlugin
    plugin_show = oscplugin.v1.plugin:ShowPlugin

Note that OSC defines the group name as :pyopenstack.<api-name>.v<version> so the version should not contain the leading 'v' character.

from osc_lib import utils


DEFAULT_API_VERSION = '1'

# Required by the OSC plugin interface
API_NAME = 'oscplugin'
API_VERSION_OPTION = 'os_oscplugin_api_version'
API_VERSIONS = {
    '1': 'oscplugin.v1.client.Client',
}

# Required by the OSC plugin interface
def make_client(instance):
    """Returns a client to the ClientManager

    Called to instantiate the requested client version.  instance has
    any available auth info that may be required to prepare the client.

    :param ClientManager instance: The ClientManager that owns the new client
    """
    plugin_client = utils.get_client_class(
        API_NAME,
        instance._api_version[API_NAME],
        API_VERSIONS)

    client = plugin_client()
    return client

# Required by the OSC plugin interface
def build_option_parser(parser):
    """Hook to add global options

    Called from openstackclient.shell.OpenStackShell.__init__()
    after the builtin parser has been initialized.  This is
    where a plugin can add global options such as an API version setting.

    :param argparse.ArgumentParser parser: The parser object that has been
        initialized by OpenStackShell.
    """
    parser.add_argument(
        '--os-oscplugin-api-version',
        metavar='<oscplugin-api-version>',
        help='OSC Plugin API version, default=' +
             DEFAULT_API_VERSION +
             ' (Env: OS_OSCPLUGIN_API_VERSION)')
    return parser

Client usage of OSC interfaces

OSC provides the following interfaces that may be used to implement the plugin commands:

# osc-lib interfaces available to plugins:
from osc_lib.cli import parseractions
from osc_lib.command import command
from osc_lib import exceptions
from osc_lib import logs
from osc_lib import utils


class DeleteMypluginobject(command.Command):
    """Delete mypluginobject"""

    ...

    def take_action(self, parsed_args):
        # Client manager interfaces are available to plugins.
        # This includes the OSC clients created.
        client_manager = self.app.client_manager

        ...

        return

OSC provides the following interfaces that may be used to implement unit tests for the plugin commands:

# OSC unit test interfaces available to plugins:
from openstackclient.tests import fakes
from openstackclient.tests import utils

...

Requirements

OSC should be included in the plugin's test-requirements.txt if the plugin can be installed as a library with the CLI being an optional feature (available when OSC is also installed).

OSC should not appear in requirements.txt unless the plugin project wants OSC and all of its dependencies installed with it. This is specifically not a good idea for plugins that are also libraries installed with OpenStack services.

python-openstackclient>=X.Y.Z # Apache-2.0

Checklist for adding new OpenStack plugins

Creating the initial plugin described above is the first step. There are a few more steps needed to fully integrate the client with openstackclient.

Add the command checker to your CI

1. Add openstackclient-plugin-jobs to the list of job templates for your project. These jobs ensures that all plugin libraries are co-installable with python-openstackclient and checks for conflicts across all OpenStackClient plugins, such as duplicated commands, missing entry points, or other overlaps.
2. Add your project to the required-projects list in the .zuul.yaml file in the openstack/openstackclient repo.

Changes to python-openstackclient

1. In doc/source/plugins.rst, update the Adoption section to reflect the status of the project.
2. Update doc/source/commands.rst to include objects that are defined by fooclient's new plugin.
3. Update doc/source/plugin-commands.rst to include the entry point defined in fooclient. We use sphinxext to automatically document commands that are used.
4. Update test-requirements.txt to include fooclient. This is necessary to auto-document the commands in the previous step.