Use service catalog to get endpoint URLs

Make use of service catalog to find endpoint URLs instead of reading from nova configuration file.

Problem description

Nova uses configuration parameters for API endpoints from the nova.conf file to communicate with other services within an OpenStack deployment. This set of services primarily includes service like Glance, Cinder and Neutron.

Ideally, these API endpoints should not be hardcoded. We should have a simple and consistent way to retrieve these endpoint URLs in Nova.

This spec focuses on using the Keystone service catalog to get API endpoints when Nova interacts with Cinder, Glance, Neutron, and others.

The service catalog is composed of a list of services which represent services in an OpenStack deployment. Each service has one or more endpoints associated with it.

Use Cases

As an operator, I want to configure the service catalog and have my services use that to interact with each other so I don’t have to individually manage inter-project connections separately.

Proposed change

The service catalog offers list of all available services along with additional information about regions, API endpoints and API versions. It is useful to efficiently find information about services such as how to configure communication between services.

Currently, Nova uses configuration settings from nova.conf file to get endpoint URLs. Each service has options in nova.conf which represent service endpoints or (e.g. in the case of cinder) ways to discover them. The option names and formats are different for each group. For example, in nova.conf, there are options like:

api_servers =,http://glance2:9292
url =
api_endpoint =
catalog_info = volumev3:cinderv3:publicURL

Keystoneauth provides a simple and consistent way to get API endpoints from the Keystone service catalog instead of configuring it in a conf file.

To make retrieving API endpoints consistent, we can add a new method get_service_url() in Nova. To establish communication with any other service, Nova will call this method to find API endpoints.

The method will first look at the existing configuration options such as [neutron]url and use these options if they exist in the configuration file. This is to ensure backwards compatibility and a smooth upgrade experience. However, the old style options will be deprecated in Pike and setting them will result in a warning being logged. The old deprecated endpoint options will be removed in the Queens release.

The exception is [glance]api_servers, which will continue to be supported. Glance needs a way to specify a list of service endpoints, and there is no such mechanism available via the service catalog.

If the existing configuration option is not found or has no value, then the method will look up the API endpoint corresponding to the conf group from the Keystone service catalog using keystoneauth.

Conf groups supporting get_service_url() will include the following set of options, based on keystoneauth1.adapter.Adapter:

  • service_type

  • service_name

  • interface

  • region_name

  • endpoint_override

If service_type is not supplied, a mapping from conf group name to corresponding service types will be consulted, and each will be tried successively until a result is found. (This mapping may be hardcoded initially, but should ultimately move to using os-client-config or service-types-authority.)

For example, a subset of the default mapping might be:

    'glance': ['image'],
    'cinder': ['block-storage', 'volumev3', 'volumev2', 'volume'],
    'ironic': ['baremetal'],
    'neutron': ['network'],

If get_service_url() is invoked for conf group cinder and [cinder]service_type is empty or missing from the conf, the method will attempt lookup with service_type='block-storage', then service_type='volumev3', etc.

If interface is not supplied, internal, admin, and public will be tried successively until a result is found. (It should be noted that publicURL is the form that has been used up until now, but public is the keystone v3 version of interface. The config should accept both, but documentation should be updated to show examples using public.)

Conf groups must also include keystone auth and session options, or may pass existing auth and/or session objects to get_service_url().

By adding this change, we will have a consistent way to connect with other services from Nova.



Data model impact


REST API impact


Security impact


Notifications impact


Other end user impact


Performance Impact


Other deployer impact

The old endpoint configuration options, except for [glance]api_servers, will be deprecated in Pike and removed in Queens.

Developer impact




Primary assignee:

Eric Fried (

Other contributors:


Work Items

  • Add methods in keystoneauth1.loading to register and list Adapter conf options in a manner similar to those existing for session and auth.

  • Add a utility method in Nova to get endpoint from service catalog.

  • Update conf groups to include the Adapter conf options.

  • Update conf groups (except Glance) to deprecate existing endpoint-related options.

  • Update Nova code using endpoints to exploit the new utility method if the legacy conf options are not specified.

  • (Queens) Remove deprecated endpoint-related conf options, and the code branches that use them.


  • Changes need to be coordinated between keystoneauth and nova.


  • Unit tests need to be added.

Documentation Impact

  • Updating admin guide for configuration related changes.





Release Name