TL;DR: I think we can handle most of oslo.context with some additions to auth_token middleware and simplify policy enforcement (from a service perspective) at the same time.
There is currently a push to release oslo.context as a library, for reference: https://github.com/openstack/oslo.context/blob/master/oslo_context/context.py Whilst I love the intent to standardize this functionality I think that many of the requirements in there are incorrect and don't apply to all services. It is my understanding for example that read_only, show_deleted are essentially nova requirements, and the use of is_admin needs to be killed off, not standardized. Currently each service builds a context based on headers made available from auth_token middleware and some additional interpretations based on that user authentication. Each service does this slightly differently based on its needs/when it copied it from nova. I propose that auth_token middleware essentially handle the creation and management of an authentication object that will be passed and used by all services. This will standardize so much of the oslo.context library that I'm not sure it will be still needed. I bring this up now as I am wanting to push this way and don't want to change things after everyone has adopted oslo.context. The current release of auth_token middleware creates and passes to services (via env['keystone.token_auth']) an auth plugin that can be passed to clients to use the current user authentication. My intention here is to expand that object to expose all of the authentication information required for the services to operate. There are two components to context that I can see: - The current authentication information that is retrieved from auth_token middleware. - service specific context added based on that user information eg read_only, show_deleted, is_admin, resource_id Regarding the first point of current authentication there are three places I can see this used: - communicating with other services as that user - associating resources with a user/project - policy enforcement Addressing each of the 'current authentication' needs: - As mentioned for service to service communication auth_token middleware already provides an auth_plugin that can be used with (at this point most) of the clients. This greatly simplifies reusing an existing token and correctly using the service catalog as each client would do this differently. In future this plugin will be extended to provide support for concepts such as filling in the X-Service-Token  on behalf of the service, managing the request id, and generally standardizing service->service communication without requiring explicit support from every project and client. - Given that this authentication plugin is built within auth_token middleware it is a fairly trivial step to provide public properties on this object to give access to the current user_id, project_id and other relevant authentication data that the services can access. This is fairly well handled today but it means it is done without the service having to fetch all these objects from headers. - With upcoming changes to policy to handle features such as the X-Service-Token the existing context will need to gain a bunch of new entries. With the keystone team looking to wrap policy enforcement into its own standalone library it makes more sense to provide this authentication object directly to policy enforcement. This will allow the keystone team to manipulate policy data from both auth_token and the enforcement side, letting us introduce new features to policy transparent to the services. It will also standardize the naming of variables within these policy files. What is left for a context object after this is managing serialization and deserialization of this auth object and any additional fields (read_only etc) that are generally calculated at context creation time. This would be a very small library. There are still a number of steps to getting there: - Adding enough data to the existing authentication plugin to allow policy enforcement and general usage. - Making the authentication object serializable for transmitting between services. - Extracting policy enforcement into a library. However I think that this approach brings enough benefits to hold off on releasing and standardizing the use of the current context objects. I'd love to hear everyone thoughts on this, and where it would fall down. I see there could be some issues with how the context would fit into nova's versioned objects for example - but I think this would be the same issues that an oslo.context library would face anyway. Jamie  This is where service->service communication includes the service token as well as the user token to allow smarter policy and resource access. For example, a user can't access certain neutron functions directly however it should be allowed when nova calls neutron on behalf of a user, or an object that a service made on behalf of a user can only be deleted when the service makes the request on behalf of that user. _______________________________________________ OpenStack-dev mailing list OpenStackfirstname.lastname@example.org http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev