Merge pull request docker#218 from livier92/update-votingapp-doc

Update doc voting apps

Author: Mano Marks

beginner/chapters/votingapp.md

@@ -82,7 +82,7 @@ services:
     depends_on:
       - db
     deploy:
-      replicas: 2
+      replicas: 1
       update_config:
         parallelism: 2
         delay: 10s
@@ -103,6 +103,8 @@ services:
         delay: 10s
         max_attempts: 3
         window: 120s
+      placement:
+        constraints: [node.role == manager]
 
   visualizer:
     image: manomarks/visualizer
@@ -111,6 +113,9 @@ services:
     stop_grace_period: 1m30s
     volumes:
       - "/var/run/docker.sock:/var/run/docker.sock"
+    deploy:
+      placement:
+        constraints: [node.role == manager]
 
 networks:
   frontend: