add note about labels

documentation/operator-guide/setup.rst

@@ -68,6 +68,23 @@ This prints out a command that can be run on a machine to join the swarm:
 
     docker swarm join --token <obtained token>
 
+It is possible to dedicate certain workers for example to contribute to ingestion exclusively, while others can take care only for rendering. This setup has benefits, when a mixed setup of nodes with different parameters is available.
+
+In order to set a node for example as `external`, to contribute in rendering only, one can simply run: 
+
+.. code-block:: bash
+
+    docker node update --label-add type=external <node-id>
+    
+Additionally, it is necessary to modify `placement` parameter in the docker compose file.
+
+.. code-block:: yaml
+
+  renderer:
+    deploy:
+      placement:
+        constraints:
+          - node.labels.type == external
 
 Additional information for swarm management can be obtained in the official
 `documentation of the project