Only update apt cache if necessary

Workarounding the upstream ansible apt module bug
documented here:

https://github.com/ansible/ansible-modules-core/pull/1517

For the next versions of ansible we'll be using, we should
check if the apt bug is fixed. When it's fixed, we could
abandon this change and use the standard apt module
with correct cache handling.

Change-Id: Id86af470197fe5b70724f0296f1cb0aed21bf826

defaults/main.yml

@@ -13,6 +13,9 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+## APT Cache Options
+cache_timeout: 600
+
 galera_server_bootstrap_node: "{{ groups['galera_all'][0] }}"
 galera_ignore_cluster_state: false
 

tasks/galera_install.yml

@@ -23,14 +23,22 @@
   tags:
     - galera-debconf
 
-- name: Update apt sources
+#TODO(evrardjp): Replace the next 2 tasks by a standard apt with cache
+#when https://github.com/ansible/ansible-modules-core/pull/1517 is merged
+#in 1.9.x or we move to 2.0 (if tested working)
+- name: Check apt last update file
+  stat:
+    path: /var/cache/apt
+  register: apt_cache_stat
+  tags:
+    - galera-apt-packages
+
+- name: Update apt if needed
   apt:
     update_cache: yes
-    cache_valid_time: 600
-  register: apt_update
-  until: apt_update|success
-  retries: 5
-  delay: 2
+  when: >
+    "ansible_date_time.epoch|float - apt_cache_stat.stat.mtime > {{cache_timeout}}" or
+    add_repos | changed
   tags:
     - galera-apt-packages
 

tasks/galera_pre_install.yml

@@ -13,14 +13,20 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-- name: Update apt sources
+#TODO(evrardjp): Replace the next 2 tasks by a standard apt with cache
+#when https://github.com/ansible/ansible-modules-core/pull/1517 is merged
+#in 1.9.x or we move to 2.0 (if tested working)
+- name: Check apt last update file
+  stat:
+    path: /var/cache/apt
+  register: apt_cache_stat
+  tags:
+    - galera-apt-packages
+
+- name: Update apt if needed
   apt:
     update_cache: yes
-    cache_valid_time: 600
-  register: apt_update
-  until: apt_update|success
-  retries: 5
-  delay: 2
+  when: "ansible_date_time.epoch|float - apt_cache_stat.stat.mtime > {{cache_timeout}}"
   tags:
     - galera-apt-packages