Cache list projects and domains for user

Listing projects and domains for a user based on their role
assignments was noted as being really slow, especially when users
have a lot of assignments. This commit implements caching to mitigate
the issue while we continue to investigate ways to speed up the
assignment API.

Change-Id: I72e398c65f01aa4f9a37f817d184a13ed01089ce
Closes-Bug: 1700852

keystone/assignment/core.py

@@ -223,7 +223,15 @@ class Manager(manager.Manager):
 
     # TODO(henry-nash): We might want to consider list limiting this at some
     # point in the future.
+    @MEMOIZE_COMPUTED_ASSIGNMENTS
     def list_projects_for_user(self, user_id):
+        # FIXME(lbragstad): Without the use of caching, listing effective role
+        # assignments is slow, especially with large data set (lots of users
+        # with multiple role assignments). This should serve as a marker in
+        # case we have the opportunity to come back and optimize this code so
+        # that it can be performant without having a hard dependency on
+        # caching. Please see https://bugs.launchpad.net/keystone/+bug/1700852
+        # for more details.
         assignment_list = self.list_role_assignments(
             user_id=user_id, effective=True)
         # Use set() to process the list to remove any duplicates
@@ -233,6 +241,7 @@ class Manager(manager.Manager):
 
     # TODO(henry-nash): We might want to consider list limiting this at some
     # point in the future.
+    @MEMOIZE_COMPUTED_ASSIGNMENTS
     def list_domains_for_user(self, user_id):
         assignment_list = self.list_role_assignments(
             user_id=user_id, effective=True)

keystone/resource/core.py

@@ -332,6 +332,11 @@ class Manager(manager.Manager):
 
             notifications.Audit.disabled(self._PROJECT, project_id,
                                          public=False)
+            # Drop the computed assignments if the project is being disabled.
+            # This ensures an accurate list of projects is returned when
+            # listing projects/domains for a user based on role assignments.
+            assignment.COMPUTED_ASSIGNMENTS_REGION.invalidate()
+
         if cascade:
             self._only_allow_enabled_to_update_cascade(project,
                                                        original_project)

releasenotes/notes/bug-1700852-de775d0eb2ddfdd1.yaml

@@ -0,0 +1,6 @@
+---
+fixes:
+  - |
+    [`bug 1700852 <https://bugs.launchpad.net/keystone/+bug/1700852>`_]
+    Keystone now supports caching of the `GET|HEAD
+    /v3/users/{user_id}/projects` API in an effort to improve performance.