python-openstackclient/doc/source/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 the setuptools entry points mechanism to advertise to OSC the plugin module and supported commands.

Implementation

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)
• 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.

DEFAULT_OSCPLUGIN_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>',
        default=utils.env(
            'OS_OSCPLUGIN_API_VERSION',
            default=DEFAULT_OSCPLUGIN_API_VERSION),
        help='OSC Plugin API version, default=' +
             DEFAULT_OSCPLUGIN_API_VERSION +
             ' (Env: OS_OSCPLUGIN_API_VERSION)')
    return parser