Improve List Role Assignments API Performance¶
As of the Havana release, keystone provides an API to list all existing role assignments in the system. However, inheritance and group assignments expasion occur at controller level in an inefficient way.
Filtering on returned list of role assignments occurs at controller level, after getting all available entities on the system from calling the manager and driver levels, which is very inefficient. This is the first problem addressed by this change proposal.
The second problem addressed is the expansion of inherited and group role assignments, which occur at controller level, when it should be placed at manager, since it is the level where additional business logic should be put.
Although not explicitly addressed in this spec, having a manager level method that lists role assignments while taking account of filtering and inheritance, would allow a number of other existing manager methods to use it rather than duplicate the inheritance and group processing logic – as it is today.
Basically, three main changes are proposed:
Propagate provided filters from controller to manager and driver levels;
Make the backend drivers consider filtering when executing list role assignment queries;
Move the code of expansion of inherited and group role assignments from the controller to the manager level.
In order to have a global view on how will be the flow of operations after the proposed change, consider the following sequence of operations:
The controller validates and passes provided filters to the manager level;
The manager checks whether effective option is used and then makes performant requests to the driver;
The driver returns the filtered list of role assignments;
If in effective mode, the manager expands inherited and group role assignments and then returns the resultant list;
The controller formats the list of entities and returns the API response.
Other End User Impact¶
The performance of the list role assignments API will be impacted positively.
In terms of memory use, since only the needed data will be coming from driver to manager level, it will be significantly decreased in the cases where filters by attributes are provided.
Regarding computational effort, since the manager will expand only inherited and group role assignments that match the provided filters, it will be significantly decreased as well.
Other Deployer Impact¶
The list role assignments method at assignment manager will become the single entry point for querying role assignments for a given user or group. It will be specially used when issuing a token, which actually uses alternative methods to compute effective role assignments.
Samuel de Medeiros Queiroz (samueldmq)
Henry Nash (henrynash)
Rodrigo Duarte Sousa (rodrigods)
In order to ensure the current behavior will not be changed by the proposed refactoring:
Implement and test restrictions on filters combinations;
Create a consistent suite of tests in order to assert the result from combining available filters.
Regarding the refactoring implementation:
Pass the filters to the driver level and return only requested role assignments;
Migrate inherited and group role assignments expansion from controller to manager.
The patches that implement this specification are already under review and may be found at the links below.