docs: public boolean existsOnBroker (String brokerId) {
          boolean result = false;
  
          PerBrokerInfo info;
          synchronized (this.brokerDetails) {
              info = this.brokerDetails.get(brokerId);
          }
  
          if ((info != null) && (info.exists)) {
              result = true;
          }
  
          return result;
      }