update docker swarm notes

docs/docker-swarm/index.md

@@ -20,6 +20,12 @@ Sometimes services get stuck or need to be forcefully updated:
 docker service update --force <service_name>
 ```
 
+To check placement and/or task history:
+
+```bash
+docker service ps <service_name> --no-trunc
+```
+
 ::: tip
 
 Sometimes if you need to force containers to restart use the update force (e.g. after restarting a node).