Add Version Responses Consistent with Openstack

Launchpad blueprint: https://blueprints.launchpad.net/barbican/+spec/fix-version-api

Barbican currently returns one-off version information for GETs to the root resource. This blueprint calls for replacing that response with an OpenStack consistent response based on json-home (see http://http://tools.ietf.org/html/draft-nottingham-json-home-03), that includes which API versions are currently supported. Such version information could facilitate automatic discovery of services when appended with the endpoint information retrieved from Keystone service catalogs for example.

Problem description

When the root resource of Barbican is queried with a GET request, it should respond with a version response consistent with other OpenStack projects, based on json-home. This was discussed at a July 2014 mid-cycle meetup for Keystone and Barbican (see https://etherpad.openstack.org/p/keystone-juno-hackathon for details). The following is an example of implementing a json-home type of response from Keystone (documented here: http://docs.openstack.org/api/openstack-identity-service/2.0/content/Versions-d1e472.html):

{
    "choices": [
        {
            "id": "v1.0",
            "status": "DEPRECATED",
            "links": [
                {
                    "rel": "self",
                    "href": "http://identity.api.openstack.org/v1.0"
                }
            ],
            "media-types": {
                "values": [
                    {
                        "base": "application/xml",
                        "type": "application/vnd.openstack.identity+xml;version=1.0"
                    },
                    {
                        "base": "application/json",
                        "type": "application/vnd.openstack.identity+json;version=1.0"
                    }
                ]
            }
        },
        {
            "id": "v1.1",
            "status": "CURRENT",
            "links": [
                {
                    "rel": "self",
                    "href": "http://identity.api.openstack.org/v1.1"
                }
            ],
            "media-types": {
                "values": [
                    {
                        "base": "application/xml",
                        "type": "application/vnd.openstack.identity+xml;version=1.1"
                    },
                    {
                        "base": "application/json",
                        "type": "application/vnd.openstack.identity+json;version=1.1"
                    }
                ]
            }
        },
        {
            "id": "v2.0",
            "status": "BETA",
            "links": [
                {
                    "rel": "self",
                    "href": "http://identity.api.openstack.org/v2.0"
                }
            ],
            "media-types": {
                "values": [
                    {
                        "base": "application/xml",
                        "type": "application/vnd.openstack.identity+xml;version=2.0"
                    },
                    {
                        "base": "application/json",
                        "type": "application/vnd.openstack.identity+json;version=2.0"
                    }
                ]
            }
        }
    ],
    "choices_links": ""
}

When a GET is performed for a specific version, version details should be provided in response such as per this Keystone example:

 {
    "version": {
        "status": "stable",
        "updated": "2014-04-17T00:00:00Z",
        "media-types": [
        {
                "base": "application/json",
                "type": "application/vnd.openstack.identity-v2.0+json"
            },
            {
                "base": "application/xml",
                "type": "application/vnd.openstack.identity-v2.0+xml"
            }
        ],
        "id": "v2.0",
        "links": [
            {
                "href": "http://23.253.228.211:5000/v2.0/",
                "rel": "self"
            },
            {
                "href": "http://docs.openstack.org/api/openstack-identity-service/2.0/content/",
                "type": "text/html",
                "rel": "describedby"
            },
            {
                "href": "http://docs.openstack.org/api/openstack-identity-service/2.0/identity-dev-guide-2.0.pdf",
                "type": "application/pdf",
                "rel": "describedby"
            }
        ]
    }
}

Proposed change

However, as Chad Lung pointed out in the Launchpad blueprint, several projects document and implement the version responses shown above, so Barbican can follow the same approach. Barbican only supports requests and response in the JSON format, so XML formats will not be supported or implemented via this blueprint.

Keystone’s keystone/controllers.py implements the GET requests and builds the version responses. Note that the MEDIA_TYPE_JSON should be ‘application/vnd.openstack.keymanagement-%s+json’. The ‘Version’ controller defined in this file is mapped to the URI path via the keystone/routers.py module. Finally the keystone/service.py module builds the final WSGI application, and includes the version routers defined in routers.py.

For Barbican then, the barbican/api/controllers/versions.py VersionController class could be modified similarly to Keystone’s controllers.py, but should be renamed to VersionsController to handle the root requests, with a new VersionController added to return specific version detail responses.

The barbican/api/app.py file should be modified to use the new VersionsController wherever VersionController is used now. Note that while the root version resource would support unauthenticated requests, specific version resource requests would require authentication.

Also, the build version information that is responded with the root resource now would still need to be provided to support automated deployment and testing processes. This blueprint proposes adding a query parameter to the root resource such as ?build_version, that would return a JSON response similar to the current one but without the version information, such as this:

{
    "build": "2014.1.dev43.g22d1a96"
}

An alternative to retrieving this build information is detailed in the Alternatives section below.

Finally, the Barbican Python client should be updated to take advantage of this new version discovery information to augment the endpoint information it retrieves from Keystone service catalogs.

Alternatives

Regarding utilizing existing frameworks to generate the version information, there does not appear to be a Python library that implements json-home.

Regarding the build version information, that is not addressed by the json-home specification, although in Appendix C of the IETF reference in a section labeled ‘Open Issues’, there appears to be a placeholder called ‘release info?’ that might address this at a future date. So perhaps we could just add the build information to the root version response.

Data model impact

None.

REST API impact

The root version response will be changed from the one-off version information returned now to the OpenStack consistent response. A specific version details response (i.e. when performing a GET on v1/ for example) will need to be added. The current root response that includes the build version would need to be modified to only return this information if a query parameter is specified.

Security impact

None.

Notifications impact

None.

Other end user impact

Any processes that rely on the current build version response would need to be modified. Clients using the Barbican Python client will need to update to the release after the changes in this blueprint are made.

Performance Impact

None.

Other deployer impact

None.

Developer impact

None.

Implementation

Assignee(s)

Primary assignee:
jaosorior
Other potential contributors:
john-wood-w chad-lung

Work Items

The following CRs would build out this blueprint:

  1. Modify version-related modules per proposal above.

2) Implement the build_version query parameter on the root resource to return the build version.

3) Update Barbican Python client code base to query the root resource for version information and then apply that to the endpoint information retrieved from the Keystone service catalog.

Dependencies

None.

Testing

Unit testing of the version resources will be added.

Documentation Impact

Update this page with API changes: https://github.com/cloudkeep/barbican/wiki/Application-Programming-Interface

References

See code and documentation references embedded in this blueprint above.

Information about json-home is found at http://http://tools.ietf.org/html/draft-nottingham-json-home-03.

Notes on the json-home discussion at the July 2014 Barbican and Keystone mid-cycle meetup can be found at https://etherpad.openstack.org/p/keystone-juno-hackathon.