Define condition for the first play host one time

We use the same condition, which defines against what host some "service"
tasks should run against, several times. It's hard to keep it the same
across the role and ansible spending additional resources to evaluate
it each time, so it's simpler and better for the maintenance to set
a boolean variable which will say for all tasks, that we want to run
only against signle host, if they should run or not now.

Change-Id: Ibdb078d39b3189c844aed14aa1ae74cb2ce97600

tasks/cinder_post_install.yml

@@ -84,7 +84,7 @@
     flat: yes
   changed_when: false
   with_items: "{{ cinder_core_files }}"
-  run_once: true
+  when: _cinder_is_first_play_host
 
 - name: Copy common config
   config_template:

tasks/main.yml

@@ -42,8 +42,7 @@
 
 - import_tasks: db_setup.yml
   when:
-    - "cinder_services['cinder-api']['group'] in group_names"
-    - "inventory_hostname == ((groups[cinder_services['cinder-api']['group']] | intersect(ansible_play_hosts)) | list)[0]"
+    - _cinder_is_first_play_host
   vars:
     _oslodb_setup_host: "{{ cinder_db_setup_host }}"
     _oslodb_databases:
@@ -57,8 +56,7 @@
 
 - import_tasks: mq_setup.yml
   when:
-    - "cinder_services['cinder-api']['group'] in group_names"
-    - "inventory_hostname == ((groups[cinder_services['cinder-api']['group']]| intersect(ansible_play_hosts)) | list)[0]"
+    - _cinder_is_first_play_host
   vars:
     _oslomsg_rpc_setup_host: "{{ cinder_oslomsg_rpc_setup_host }}"
     _oslomsg_rpc_userid: "{{ cinder_oslomsg_rpc_userid }}"
@@ -129,9 +127,7 @@
 
 - import_tasks: cinder_db_sync.yml
   when:
-    - "groups['cinder_api'] | length > 0"
-    - "cinder_services['cinder-api']['group'] in group_names"
-    - "inventory_hostname == ((groups['cinder_api'] | intersect(ansible_play_hosts)) | list)[0]"
+    - _cinder_is_first_play_host
   tags:
     - cinder-config
 
@@ -160,9 +156,7 @@
         password: "{{ cinder_service_password }}"
         role: "{{ cinder_service_role_name }}"
   when:
-    - "groups['cinder_api'] | length > 0"
-    - "cinder_services['cinder-api']['group'] in group_names"
-    - "inventory_hostname == ((groups['cinder_api'] | intersect(ansible_play_hosts)) | list)[0]"
+    - "_cinder_is_first_play_host"
   tags:
     - cinder-config
 
@@ -200,7 +194,6 @@
 - import_tasks: cinder_backends.yml
   when:
     - "groups[cinder_services['cinder-volume']['group']] | length > 0"
-    - "cinder_services['cinder-api']['group'] in group_names"
-    - "inventory_hostname == ((groups[cinder_services['cinder-api']['group']] | intersect(ansible_play_hosts)) | list)[-1]"
+    - "_cinder_is_first_play_host"
   tags:
     - cinder-config

vars/main.yml

@@ -13,6 +13,8 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+_cinder_is_first_play_host: "{{ (cinder_services['cinder-api']['group'] in group_names and inventory_hostname == (groups[cinder_services['cinder-api']['group']] | intersect(ansible_play_hosts)) | first) | bool }}"
+
 _cinder_rootwrap_conf_overrides:
   DEFAULT:
     filters_path: "/etc/cinder/rootwrap.d,/usr/share/cinder/rootwrap"