start-first, remove default env vars

compose.yml

@@ -15,8 +15,6 @@ services:
       - DISCOURSE_DATABASE_USER=discourse
       - DISCOURSE_DATABASE_NAME=discourse
       - DISCOURSE_DATABASE_PASSWORD_FILE=/run/secrets/db_password
-      - DISCOURSE_REDIS_HOST=redis
-      - DISCOURSE_REDIS_PORT_NUMBER=6379
       - DISCOURSE_SMTP_HOST
       - DISCOURSE_SMTP_PORT
       - DISCOURSE_SMTP_USER
@@ -30,8 +28,9 @@ services:
       - db
       - redis
     deploy:
-      restart_policy:
-        condition: on-failure
+      update_config:
+        failure_action: rollback
+        order: start-first
       labels:
         - "traefik.enable=true"
         - "traefik.http.services.${STACK_NAME}.loadbalancer.server.port=3000"