Add automatic restart for RabbitMQ

This patch ensures that systemd will restart RabbitMQ in case of
failure or if the process is manually killed.

Closes-Bug: 1659954
Change-Id: Id8dbdccfe445f4a25902054eb6809d42a92d5f5d

tasks/rabbitmq_post_install.yml

@@ -60,10 +60,20 @@
     - rabbitmq-config
 
 - name: Apply resource limits (systemd)
-  register: rabbit_resource_limit_changed
   template:
     src: "limits.conf.j2"
     dest: "/etc/systemd/system/rabbitmq-server.service.d/limits.conf"
+  register: rabbit_resource_limit
+  when:
+    - ansible_service_mgr == 'systemd'
+  tags:
+    - rabbitmq-config
+
+- name: Add automatic restart on failure
+  template:
+    src: systemd-restart-on-failure.conf.j2
+    dest: "/etc/systemd/system/rabbitmq-server.service.d/systemd-restart-on-failure.conf"
+  register: rabbit_restart_on_failure
   when:
     - ansible_service_mgr == 'systemd'
   tags:
@@ -73,7 +83,8 @@
   command: "systemctl daemon-reload"
   when:
     - ansible_service_mgr == 'systemd'
-    - rabbit_resource_limit_changed|changed
+    - rabbit_resource_limit | changed
+    - rabbit_restart_on_failure | changed
   tags:
     - rabbitmq-config
     # don't trigger ANSIBLE0016

templates/systemd-restart-on-failure.conf.j2

@@ -0,0 +1,4 @@
+# {{ ansible_managed }}
+[Service]
+Restart=on-failure
+RestartSec=2