Only execute this role, if required variables are defined

defaults/main.yml

 ---
 
+elasticsearch_install: yes
 elasticsearch:
   purge:
     - index: logstash

tasks/main.yml

@@ -34,4 +34,4 @@
         - Config
       when: elasticsearch.snapshot is defined and elasticsearch.snapshot.indices is defined
 
-  when: (not excluded_roles or "elasticsearch" not in excluded_roles) and 'logserver' in groups and inventory_hostname in groups.logserver
+  when: elasticsearch_install and (not excluded_roles or "elasticsearch" not in excluded_roles) and 'logserver' in groups and inventory_hostname in groups.logserver