private static void applyDefaultPreload(List<ApplicationContainer> containers, Element nodesElement) {
        if (! nodesElement.hasAttribute(VespaDomBuilder.PRELOAD_ATTRIB_NAME)) return;
        for (Container container: containers)
            container.setPreLoad(nodesElement.getAttribute(VespaDomBuilder.PRELOAD_ATTRIB_NAME));
    }
Allocate a container cluster without a nodes tag
config-model/src/main/java/com/yahoo/vespa/model/container/xml/ContainerModelBuilder.java