code: private boolean isAttributeRegistrationAllowed(AttributeDefinition definition) {
          boolean runtime = definition.getImmutableFlags().contains(AttributeAccess.Flag.STORAGE_RUNTIME);
          if (!runtime) {
              return true;
          }
          boolean runtimeServiceNotRequired = definition.getImmutableFlags().contains(AttributeAccess.Flag.RUNTIME_SERVICE_NOT_REQUIRED);
          if (runtimeServiceNotRequired) {
              return true;
          }
          return getProcessType().isServer();
      }
docs: Metrics and runtime attributes are always registered in the MMR only for normal server.
  If they are flagged with {@link AttributeAccess.Flag#STORAGE_RUNTIME} and
  {@link AttributeAccess.Flag#RUNTIME_SERVICE_NOT_REQUIRED}, they are registered regardless of the process type.