code: private boolean tryToDispatchTokens(MessageHolderWithTokens msg) {
          try {
              dispatchTokensEvent.fire(msg);
              return true;
          } catch (MessageDeliveryException e) {
              Throwable cause = e.getCause();
              if (isQueueFullException(cause)) {
                  return false;
              }
              throw e;
          }
      }
docs: Tries to dispatch tokens; returns true if tokens were successfully queued.
  Detects when queue is full and in that case returns false.
  
  @return returns true if tokens were successfully queued; returns false if queue was full