code: public MasterConnectionInfo masterConnectionInfo() {
          if (!isMaster())
              throw new IllegalStateException("Unable to determine master connection info. This is a slave node");
          return MasterConnectionInfo.builder().connectionUrl(subscriber.connectionUrl())
                          .responderUrl(responder.connectionUrl()).slaveUrls(new ArrayList<>()).build();
      }
docs: When this is a master node,
  it returns the connection url for this node,
  it's slaves (if any exist) and the responder
  connection url in the form of:
  host:port:streamId
  
  @return the master connection info