API Extensions¶
API extensions provide a standardized way of introducing new API functionality.
While the neutron-lib
project itself does not serve an API, the neutron
project does and leverages the API extension framework from neutron-lib
.
API extensions consist of the following high-level constructs:
API definitions that specify the extension’s static metadata. This metadata includes basic details about the extension such as its name, description, alias, etc. as well as its extended resources/sub-resources and required/optional extensions. These definitions live in the
neutron_lib.api.definitions
package.API reference documenting the APIs/resources added/modified by the extension. This documentation is in
rst
format and is used to generate the OpenStack Networking API reference. The API reference lives under theapi-ref/source/v2
directory of theneutron-lib
project repository.An extension descriptor class that must be defined in an extension directory for
neutron
or other sub-project that supports extensions. This concrete class provides the extension’s metadata to the API server. These extension classes reside outside ofneutron-lib
, but leverage the base classes fromneutron_lib.api.extensions
. For more details see the section below on using neutron-lib’s extension classes.The API extension plugin implementation itself. This is the code that implements the extension’s behavior and should carry out the operations defined by the extension. This code resides under its respective project repository, not in
neutron-lib
. For more details see the neutron api extension dev-ref.
Using neutron-lib’s base extension classes¶
The neutron_lib.api.extensions
module provides a set of base extension
descriptor classes consumers can use to define their extension descriptor(s).
For those extensions that have an API definition in
neutron_lib.api.definitions
, the APIExtensionDescriptor
class can
be used. For example:
from neutron_lib.api.definitions import provider_net
from neutron_lib.api import extensions
class Providernet(extensions.APIExtensionDescriptor):
api_definition = provider_net
# nothing else needed if default behavior is acceptable
For extensions that do not yet have a definition in
neutron_lib.api.definitions
, they can continue to use the
ExtensionDescriptor
as has been done historically.