code: protected boolean doDelivery(DeliveryRequest request) {
          final String methodName = "doDelivery";
          logger.entry(this, methodName, request);
  
          final SubData sd =
                  subscribedDestinations.get(new SubscriptionTopic(request.topicPattern));
          boolean result = false;
          if (sd == null) {
              logger.data(methodName, "subscribedDestination not found for " + request.topicPattern);
          } else if (sd.state == SubData.State.ESTABLISHED) {
              result = (request.qos == QOS.AT_MOST_ONCE || sd.pendingDeliveries.contains(request));
              if (result) {
                  engine.tell(new DeliveryResponse(request), this);
              }
          } else {
              logger.data(methodName, "subscription not in ESTABLISHED state for: " + sd);
          }
  
          logger.exit(this, methodName, result);
          return result;
      }
docs: Pass a {@link DeliveryResponse} back to the engine which will settle the delivery (in the
  AT_LEAST_ONCE case) and flow deliveryCount++ and link-credit to the remote end
  
  @param request the {@link DeliveryRequest} to process.
  @return true == it might have worked, false == it really didn't work!