update docker compose file for docker swarm

Author: James Lee

prod.yml

@@ -5,8 +5,20 @@ services:
       file: common.yml
       service: dockerapp
     image: jleetutorial/dockerapp
+    environment:
+      - constraint:node==master
+    depends_on:
+      - redis
+    networks:
+      - mynet
 
   redis:
     extends:
       file: common.yml
       service: redis
+    networks:
+      - mynet
+
+networks:
+  mynet:
+    driver: overlay