@Override
  protected void registerEventDroppedInPrimaryQueue(EntryEventImpl droppedEvent) {
    sendBatchDestroyOperationForDroppedEvent(droppedEvent, -1);
  }
Initialize the Executor that handles listener events. Only used by non-primary gateway senders
geode-core/src/main/java/org/apache/geode/internal/cache/wan/serial/SerialGatewaySenderEventProcessor.java