Second pass at Docker MTU assignment

ansible/roles/docker/tasks/config.yml

@@ -5,4 +5,3 @@
     dest: /etc/docker/daemon.json
   become: True
   notify: restart docker service
-

ansible/roles/docker/tasks/main.yml

@@ -6,6 +6,12 @@
     append: yes
   become: True
 
+- name: Check Docker state with systemd
+  service:
+    name: docker
+    state: started
+  become: True
+
 - name: Check whether docker storage is in loopback mode
   command: docker info
   register: docker_info
@@ -25,15 +31,4 @@
 - include: storage.yml
   when: "{{ 'Data loop file' in docker_info.stdout }}"
 
-- name: Read Docker daemon config file
-  slurp:
-    src: /etc/docker/daemon.json
-  register: docker_daemon_conf
-  become: True
-
-- name: Parse Docker daemon config JSON
-  set_fact:
-    docker_daemon_json: "{{ docker_daemon_conf['content'] | b64decode | from_json }}"
-
 - include: config.yml
-  when: "{{ docker_daemon_json['mtu'] }} != 1450 or {{ docker_daemon_json['storage-driver'] }} != 'devicemapper'"

ansible/roles/docker/templates/daemon.json.j2

@@ -1,6 +1,6 @@
 {
   "storage-driver": "devicemapper",
-  "mtu": 1450,
+  "mtu": {{ external_net_name | net_mtu }},
   "storage-opts": [
     "dm.thinpooldev=/dev/mapper/{{ docker_storage_volume_group | replace('-', '--') }}-{{ docker_storage_volume_thinpool | replace('-', '--') }}",
     "dm.use_deferred_removal=true",