[HIVE-9550] ObjectStore.getNextNotification() can return events inside NotificationEventResponse as null which conflicts with its thrift "required" tag

• Type: Sub-task
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 1.2.0
• Assignee: Sushanth Sowmyan
• Reporter: Sushanth Sowmyan
• Created: 02/Feb/15 20:58
• Updated: 01/Oct/19 22:07
• Resolved: 04/Feb/15 19:18

Description

Per hive_metastore.thrift, the "events" list inside NotificationEventResponse is a required field that cannot be null.

struct NotificationEventResponse {
    1: required list<NotificationEvent> events,
}

However, per ObjectStore.java, this events field can be uninitialized if the events retrieved from the metastore is empty instead of null:

      NotificationEventResponse result = new NotificationEventResponse();
      int maxEvents = rqst.getMaxEvents() > 0 ? rqst.getMaxEvents() : Integer.MAX_VALUE;
      int numEvents = 0; 
      while (i.hasNext() && numEvents++ < maxEvents) {
        result.addToEvents(translateDbToThrift(i.next()));
      }    
      return result;

The fix is simple enough - we need to call result.setEvents(new ArrayList<NotificationEvent>()) before we begin the iteration to do result.addToEvents(...).