Hive meta store returns null response when there is no new notification. Thrift throws exception with this null response, and calling HiveMetaStoreClient.getNextNotification gets this exception.
The desired behavior is that Hive meta store returns normal response with set event. And the events set is empty.
This bug is tracked in https://issues.apache.org/jira/browse/HIVE-15761
We need to add a unit test to expose this bug in Hive meta store. And Hive team can easily verify the fix with this unit test.