code: protected synchronized void sendCommandToShard(VoidMessage message) {
          // if this node is shard - we just step over TCP/IP infrastructure
          // TODO: we want LocalTransport to be used in such cases
          if (nodeRole == NodeRole.SHARD) {
              message.setTargetId(shardIndex);
              messages.add(message);
              return;
          }
  
  
          //log.info("Sending CS: {}", message.getClass().getCanonicalName());
  
          message.setTargetId(targetIndex);
          DirectBuffer buffer = message.asUnsafeBuffer();
  
          long result = publicationForShards.offer(buffer);
  
          if (result < 0)
              for (int i = 0; i < 5 && result < 0; i++) {
                  try {
                      // TODO: make this configurable
                      Thread.sleep(1000);
                  } catch (Exception e) {
                  }
                  result = publicationForShards.offer(buffer);
              }
  
          // TODO: handle retransmit & backpressure separately
  
          if (result < 0)
              throw new RuntimeException("Unable to send message over the wire. Error code: " + result);
      }
docs: This command is possible to issue only from Client
  
  @param message