private AddServiceInfo validate(Cluster cluster, AddServiceRequest request) {
    LOG.info("Validating {}", request);

    RequestValidator validator = requestValidatorFactory.create(request, cluster);
    validator.validate();

    return validator.createValidServiceInfo(actionManager, requestFactory);
  }
Performs basic validation of the request and
fills in details about the requested services and components.

@return validated information about the requested services
ambari-server/src/main/java/org/apache/ambari/server/topology/addservice/AddServiceOrchestrator.java