private ContainerDocproc buildDocproc(DeployState deployState, ApplicationContainerCluster cluster, Element spec) {
        Element docprocElement = XML.getChild(spec, "document-processing");
        if (docprocElement == null)
            return null;

        addIncludes(docprocElement);
        DocprocChains chains = new DomDocprocChainsBuilder(null, false).build(deployState, cluster, docprocElement);

        ContainerDocproc.Options docprocOptions = DocprocOptionsBuilder.build(docprocElement, deployState.getDeployLogger());
        return new ContainerDocproc(cluster, chains, docprocOptions, !standaloneBuilder);
     }
Allocate a container cluster without a nodes tag
config-model/src/main/java/com/yahoo/vespa/model/container/xml/ContainerModelBuilder.java