Verify if hosts file already managed with OSA

With this patch we ensure that duplicated records are not
created with rabbitmq role if hosts file already contain
OSA managed block. Managing hosts still might be required for
role usage outside of the OSA so we workaround this usecase.

Change-Id: Ia20902f0ffe21ce563966fee4d233e5ec3afe3d9
Related-Bug: #1960587

defaults/main.yml

@@ -29,8 +29,10 @@ rabbitmq_node_address: "{{ ansible_host }}"
 rabbit_system_user_name: rabbitmq
 rabbit_system_group_name: rabbitmq
 
-# Hosts file entries (set this to an empty list to disable /etc/hosts generation
-# for the rabbitmq cluster nodes)
+# Allow role to adjust /etc/hosts file
+rabbitmq_manage_hosts_entries: True
+
+# Hosts file entries
 rabbitmq_hosts_entries: >-
   {{ groups[rabbitmq_host_group] | map('extract', hostvars) | list |
      json_query(

releasenotes/notes/rabbitmq_manage_hosts-834150c45dfc0771.yaml

@@ -0,0 +1,9 @@
+---
+features:
+  - |
+    Added variable ``rabbitmq_manage_hosts_entries`` that controls if
+    rabbitmq_server role will attempt to adjust /etc/hosts file
+fixes:
+  - |
+    Do not duplicate records in /etc/hosts file by rabbitmq role when hosts
+    file is already managed by OSA.

tasks/rabbitmq_pre_install.yml

@@ -30,21 +30,27 @@
     - rabbitmq-package-rpm
     - rabbitmq-package-rpm-get
 
-- name: Fix /etc/hosts
-  lineinfile:
-    dest: /etc/hosts
-    state: present
-    line: "{{ item.address }} {{ item.hostnames | join(' ') }}"
-  with_items: "{{ rabbitmq_hosts_entries }}"
-  tags:
-    - rabbitmq-config
-
-- name: Ensure localhost /etc/hosts entry is correct
-  lineinfile:
-    dest: /etc/hosts
-    state: present
-    line: '127.0.0.1 localhost'
-    regexp: '^127.0.0.1'
+- name: Manage /etc/hosts files
+  block:
+    - name: Fail if hosts file is not managed yet
+      command: grep "OPENSTACK-ANSIBLE MANAGED BLOCK" /etc/hosts
+      changed_when: false
+  rescue:
+    - name: Rescue failure and add required records
+      lineinfile:
+        dest: /etc/hosts
+        state: present
+        line: "{{ item.address }} {{ item.hostnames | join(' ') }}"
+      with_items: "{{ rabbitmq_hosts_entries }}"
+  always:
+    - name: Ensure localhost /etc/hosts entry is correct
+      lineinfile:
+        dest: /etc/hosts
+        state: present
+        line: '127.0.0.1 localhost'
+        regexp: '^127\.0\.0\.1'
+  when:
+    - rabbitmq_manage_hosts_entries | bool
   tags:
     - rabbitmq-config