Merge "Improve way of cache backend selection"

defaults/main.yml

@@ -357,6 +357,8 @@ keystone_memcached_servers: "{{ memcached_servers }}"
 # The cache_servers default backend is memcached, so this variable
 # should point to a list of memcached servers.
 # If empty, caching is disabled.
+keystone_cache_backend: "{{ openstack_cache_backend | default('oslo_cache.memcache_pool') }}"
+keystone_cache_backend_map: "{{ openstack_cache_backend_map | default(_keystone_cache_backend_map) }}"
 keystone_cache_servers: "{{ keystone_memcached_servers.split(',') }}"
 
 ## LDAP Section
@@ -572,8 +574,7 @@ keystone_pip_packages:
   - ldappool
   - osprofiler
   - PyMySQL
-  - pymemcache
-  - python-memcached
+  - "{{ _keystone_cache_backend_package }}"
   - python-openstackclient
   - systemd-python
   - uWSGI

releasenotes/notes/cache_backend-3ac67f78fa111445.yaml

@@ -0,0 +1,10 @@
+---
+features:
+  - |
+    New variables have been added to manage used cache backends:
+
+      * ``openstack_cache_backend``: defines driver, that will be used for
+        caching.
+        Default: oslo_cache.memcache_pool
+      * ``openstack_cache_backend_map``: maps selected backend to
+        the oslo driver that should be installed and configured for it.

templates/keystone.conf.j2

@@ -43,13 +43,15 @@ transport_url = {{ keystone_oslomsg_notify_transport }}://{% for host in keyston
 
 {% if keystone_cache_servers | length > 0 %}
 [cache]
-backend = oslo_cache.memcache_pool
+backend = {{ keystone_cache_backend }}
+{% if keystone_cache_backend in keystone_cache_backend_map['dogpile'] %}
 # FIXME(lbragstad): Some strange behaviors have been reported when using
 # multiple memcached instances with backend_argument. This has been documented
 # in https://bugs.launchpad.net/oslo.cache/+bug/1743036
 # For the time being, memcache_servers works with a single memcached instance
 # and multiple instances.
 memcache_servers = {{ keystone_cache_servers | join(',') }}
+{% endif %}
 config_prefix = cache.keystone
 enabled = true
 {% endif %}

vars/main.yml

@@ -37,3 +37,22 @@ uwsgi_keystone_services: |-
 
 _keystone_is_first_play_host: "{{ (keystone_services['keystone-wsgi-public']['group'] in group_names and inventory_hostname == ((groups[keystone_services['keystone-wsgi-public']['group']] | intersect(ansible_play_hosts)) | list)[0]) | bool }}"
 _keystone_is_last_play_host: "{{ (keystone_services['keystone-wsgi-public']['group'] in group_names and inventory_hostname == ((groups[keystone_services['keystone-wsgi-public']['group']] | intersect(ansible_play_hosts)) | list)[-1]) | bool }}"
+_keystone_cache_backend_map:
+  dogpile:
+    - oslo_cache.memcache_pool
+    - dogpile.cache.pymemcache
+    - dogpile.cache.memcached
+    - dogpile.cache.bmemcached
+  mongo:
+    - oslo_cache.mongo
+  etcd3gw:
+    - oslo_cache.etcd3gw
+
+_keystone_cache_backend_package: |-
+    {% set oslo = namespace(backend='dogpile') %}
+    {% for key, value in _keystone_cache_backend_map.items() %}
+    {%   if keystone_cache_backend in value %}
+    {%     set oslo.backend = key %}
+    {%-   endif %}
+    {%- endfor %}
+    oslo.cache[{{ oslo.backend }}]