dont call ensure_indexes on slave #1338

Author: Erdenezul Batmunkh

mongoengine/document.py

@@ -195,7 +195,9 @@ def _get_collection(cls):
 
             # Ensure indexes on the collection unless auto_create_index was
             # set to False.
-            if cls._meta.get('auto_create_index', True):
+            # Also there is no need to ensure indexes on slave.
+            if cls._meta.get('auto_create_index', True) and\
+                    db.client.is_primary:
                 cls.ensure_indexes()
 
         return cls._collection