[designate] Add coordination backend for designate workers

Add coordination backend configuration to designate.conf which is
required in multinode environments. Fixes warning from designate:

WARNING designate.coordination [-] No coordination backend configured,
assuming we are the only worker. Please configure a coordination backend

Change-Id: I23c4d2de7e3f9368795c423000a4f9a6c3a431e2
Closes-Bug: #1843842
Related-Bug: #1840070

ansible/group_vars/all.yml

@@ -869,6 +869,8 @@ designate_backend: "bind9"
 designate_ns_record: "sample.openstack.org"
 designate_backend_external: "no"
 designate_backend_external_bind9_nameservers: ""
+# Valid options are [ '', redis, etcd ]
+designate_coordination_backend: "{{ 'redis' if enable_redis|bool else 'etcd' if enable_etcd|bool else '' }}"
 
 #######################
 # Neutron options

ansible/roles/designate/templates/designate.conf.j2

@@ -114,3 +114,11 @@ enable_proxy_headers_parsing = True
 [oslo_policy]
 policy_file = {{ designate_policy_file }}
 {% endif %}
+
+[coordination]
+{% if designate_coordination_backend == 'redis' %}
+backend_url = {{ redis_connection_string }}
+{% elif designate_coordination_backend == 'etcd' %}
+# NOTE(noxoid): python-etcd3 does not support multiple endpoints
+backend_url = etcd3://{{ hostvars[groups['etcd'][0]]['ansible_' + hostvars[groups['etcd'][0]]['api_interface']]['ipv4']['address'] }}:{{ etcd_client_port }}
+{% endif %}

doc/source/reference/networking/designate-guide.rst

@@ -37,6 +37,13 @@ Configure Designate options in ``/etc/kolla/globals.yml``
    dns_interface: "eth1"
    designate_ns_record: "sample.openstack.org"
 
+.. important::
+
+   If multiple nodes are assigned to be Designate workers then you must
+   enable a supported coordination backend, currently either 'redis' or
+   'etcd'. The backend choice can be overridden by the
+   ``designate_coordination_backend`` variable.
+
 The following additional variables are required depending on which backend you
 intend to use:
 

etc/kolla/globals.yml

@@ -439,6 +439,8 @@
 # Valid options are [ bind9 ]
 #designate_backend: "bind9"
 #designate_ns_record: "sample.openstack.org"
+# Valid options are [ '', redis, etcd ]
+#designate_coordination_backend: "{{ 'redis' if enable_redis|bool else 'etcd' if enable_etcd|bool else '' }}"
 
 ########################
 # Nova - Compute Options

releasenotes/notes/new-variable-designate-coordination-backend-741ec71946e7567e.yaml

@@ -0,0 +1,7 @@
+---
+features:
+  - |
+    Designate coordination backend can now be configured via the
+    designate_coordination_backend variable. Coordination is mandatory
+    when multiple workers are deployed as in a multinode environment.
+    Possible values are redis or etcd.