Cache loaded plugins in memory

common/lib/xmodule/x_module.py

@@ -23,6 +23,9 @@ class Plugin(object):
 
         entry_point: The name of the entry point to load plugins from
     """
+
+    _plugin_cache = None
+
     @classmethod
     def load_class(cls, identifier, default=None):
         """
@@ -33,6 +36,10 @@ class Plugin(object):
         If default is not None, will return default if no entry_point matching identifier
         is found. Otherwise, will raise a ModuleMissingError
         """
+        if cls._plugin_cache is None:
+            cls._plugin_cache = {}
+
+        if identifier not in cls._plugin_cache:
             identifier = identifier.lower()
             classes = list(pkg_resources.iter_entry_points(cls.entry_point, name=identifier))
             if len(classes) > 1:
@@ -46,7 +53,8 @@ class Plugin(object):
                     return default
                 raise ModuleMissingError(identifier)
 
-        return classes[0].load()
+            cls._plugin_cache[identifier] = classes[0].load()
+        return cls._plugin_cache[identifier]
 
     @classmethod
     def load_classes(cls):