private static void validateAndAddConfiguredComponents(DeployState deployState,
                                                           ContainerCluster<? extends Container> cluster,
                                                           Element spec,
                                                           String componentName,
                                                           Consumer<Element> elementValidator) {
        for (Element node : XML.getChildren(spec, componentName)) {
            elementValidator.accept(node); // throws exception here if something is wrong
            cluster.addComponent(new DomComponentBuilder().build(deployState, cluster, node));
        }
    }
Allocate a container cluster without a nodes tag
config-model/src/main/java/com/yahoo/vespa/model/container/xml/ContainerModelBuilder.java