added named volume for data container

improved discovery of masters

templates/es-cluster/0/docker-compose.yml

@@ -11,6 +11,7 @@ services:
             - "bootstrap.memory_lock=true"
             - "xpack.security.enabled=false"
             - "ES_JAVA_OPTS=-Xms${heap_size} -Xmx${heap_size}"
+            - "discovery.zen.ping.unicast.hosts=es-master"
             - "discovery.zen.minimum_master_nodes=${minimum_master_nodes}"
             - "node.master=true"
         ulimits: 
@@ -62,7 +63,7 @@ services:
         image: docker.elastic.co/elasticsearch/elasticsearch:5.3.0
         entrypoint: /bin/true
         volumes: 
-            - /usr/share/elasticsearch/data
+            - es-data-volume:/usr/share/elasticsearch/data
 
     kibana:
         labels: 
@@ -79,3 +80,8 @@ services:
             - "${kibana_port}:5601"
         depends_on:
             - es-master
+
+volumes:
+  es-data-volume:
+    driver: local
+    per_container: true