Add optional fallback DNS servers to resolvconf

(cherry picked from commit 6f61a337d6335244dcf4946a4e460b822fb90c5f)

CHANGELOG.md

+- Role: common
+  - Added `COMMON_FALLBACK_DNS_SERVERS`, which optionally adds additional `nameserver` entries to the resolvconf tail
+  - Explicitly added `resolvconf` as a dependency
+
 - Role: edxapp
   - Added creation of enterprise_worker user to provisioning. This user is used by the edx-enterprise package when making API requests to Open edX IDAs.
 

playbooks/roles/common/tasks/main.yml

@@ -145,6 +145,19 @@
   shell: hostname -F /etc/hostname
   when: COMMON_HOSTNAME|length >0 and (etc_hosts.changed or etc_hostname.changed)
 
+- name: Add fallback DNS servers to resolvconf
+  lineinfile:
+    dest: /etc/resolvconf/resolv.conf.d/tail
+    line: "nameserver {{ item }}"
+    create: yes
+    state: present
+  with_items: "{{ COMMON_FALLBACK_DNS_SERVERS }}"
+
+- name: restart networking
+  service:
+    name: networking
+    state: restarted
+
 - name: Copy the templates to their respestive destination
   template:
     dest: "{{ item.dest }}"

playbooks/roles/common_vars/defaults/main.yml

@@ -66,6 +66,9 @@ COMMON_GIT_PATH: 'edx'  # git path prefix
 # override this var to set a different hostname
 COMMON_HOSTNAME: ""
 
+# List of DNS server addresses to append to resolvconf
+COMMON_FALLBACK_DNS_SERVERS: []
+
 # Set to true to customize DNS search domains
 COMMON_CUSTOM_DHCLIENT_CONFIG: false
 # uncomment and specifity your domains.
@@ -108,6 +111,7 @@ common_redhat_pkgs:
   - git
   - unzip
   - acl
+  - resolvconf
 common_debian_pkgs:
   - apt-transport-https
   - ntp
@@ -119,6 +123,7 @@ common_debian_pkgs:
   - unzip
   - python-pip
   - python2.7-dev
+  - resolvconf
 
 # Packages that should be installed from our custom PPA, i.e. COMMON_EDX_PPA
 old_python_debian_pkgs: