Raise an overlimit exception when overlimit/bound

delimiter/drivers/zookeeper.py

@@ -111,11 +111,7 @@ class ZookeeperQuotaEngine(engine.QuotaEngine):
             raise ValueError("Unsupported kind '%s' encountered"
                              " for resource '%s' owned by '%s'"
                              % (kind, resource, for_who))
-        if not processor.process(stored['details'], amount):
-            raise ValueError("Limit reached, '%s' can not"
-                             " consume '%s' of '%s'" % (for_who,
-                                                        resource, amount))
-        return stored
+        return processor.process(stored['details'], amount)
 
     def consume_many(self, for_who, resources, amounts):
         who_path = paths.join(self.uri.path, for_who)

delimiter/exceptions.py

@@ -16,3 +16,7 @@
 
 class DelimiterException(Exception):
     """Base class for *most* exceptions emitted from this library."""
+
+
+class OverLimitException(DelimiterException):
+    """Exception raised when over some limit."""

delimiter/processors.py

@@ -14,6 +14,9 @@
 #    under the License.
 
 
+from delimiter import exceptions
+
+
 class UpperBoundProcessor(object):
     """Processes a limit given some upper bound."""
 
@@ -34,8 +37,8 @@ class UpperBoundProcessor(object):
     def process(self, details, amount):
         consumed = details['consumed']
         if consumed + amount > details['bound']:
-            return False
+            raise exceptions.OverLimitException
         else:
             details = details.copy()
             details['consumed'] = consumed + amount
-            return True
+            return details