Use the clustering logic we use with rabbit.

playbooks/roles/elasticsearch/templates/elasticsearch.yml.j2

+
+# Path to directory where to store index data allocated for this node.
+#
+path.data: {{elasticsearch_data_dir}}
+
+
+# Path to log files:
+#
+path.logs: {{elasticsearch_log_dir}}
+
+# ElasticSearch performs poorly when JVM starts swapping: you should ensure that
+# it _never_ swaps.
+#
+# Set this property to true to lock the memory:
+#
+bootstrap.mlockall: true
+
+# Unicast discovery allows to explicitly control which nodes will be used
+# to discover the cluster. It can be used when multicast is not present,
+# or to restrict the cluster communication-wise.
+#
+# 1. Disable multicast discovery (enabled by default):
+#
+# discovery.zen.ping.multicast.enabled: false
+#
+# 2. Configure an initial list of master nodes in the cluster
+#    to perform discovery when new nodes (master or data) are started:
+#
+# discovery.zen.ping.unicast.hosts: ["host1", "host2:port", "host3[portX-portY]"]
+{%- if ELASTICSEARCH_CLUSTERED -%}
+{%- set hosts= [] -%}
+{%- set all_elasticsearch_hosts = [] -%}
+{%- do all_elasticsearch_hosts.extend(groups.tag_role_elasticsearch) -%}
+{%- do all_elasticsearch_hosts.extend(groups.tag_group_elasticsearch) -%}
+{%- for name in  group_names -%}
+  {%- if name.startswith(elasticsearch_aws_stack_name) -%}
+    {%- for host in all_elasticsearch_hosts -%}
+      {%- if host in groups[name] -%}
+        {% do hosts.append(host) %}
+      {%- endif -%}
+    {%- endfor -%}
+  {%- endif -%}
+{%- endfor -%}
+
+[{rabbit,
+  [{cluster_nodes, {['{{ hosts|join("\',\'") }}'], disc}}]}].
+
+{%- else -%}
+
+{%- endif -%}