Comment 20 for bug 1590779

Reviewed: https://review.openstack.org/369618
Committed: https://git.openstack.org/cgit/openstack/keystone/commit/?id=f1d9c54ef07c61cb80def5779802cc4daf45f4cb
Submitter: Jenkins
Branch: stable/mitaka

commit f1d9c54ef07c61cb80def5779802cc4daf45f4cb
Author: David Stanek <email address hidden>
Date: Mon Aug 1 21:06:50 2016 +0000

    Distributed cache namespace to invalidate regions

    dogpile.cache's region invalidation is not designed to work across
    processes. This patch enables distributed invalidation of keys in a
    region.

    Instead of using a static cache key, we use the original cache key
    and append a dynamic value to it. This value is looked up in
    memcached using the region name as a key. So anytime the value of
    the region key changes the cache keys in that region are
    effectively invalidated.

    Conflicts:
     keystone/assignment/core.py: imports were fixed
     keystone/catalog/core.py: imports were fixed
     keystone/common/cache/core.py:
                    dogpile.cache doesn't have invalidation strategies
                    in 0.5.8. Because of that, call to
                    region.invalidate was redefined.
     keystone/identity/core.py:
                    there is no per-region cache in id_mapping_api
                    in Mitaka
     keystone/revoke/core.py:
                    there is no per-region cache in revocations
                    in Mitaka
     keystone/server/backends.py:
                    removed configuration of regions which were added
                    only in Newton
     keystone/tests/unit/test_v3_assignment.py:
                    conflict due to freezegun being used in Newton and
                    not used in Mitaka
     keystone/token/provider.py:
                    there is no per-region cache in token providers
                    in Mitaka

    Closes-Bug: #1590779
    Change-Id: Ib80d41d43ef815b37282d72ad68e7aa8e1ff354e
    (cherry picked from commit 42eda48c78f1153081b4c193dc13c88561409fd3)