private void setCpuSocketAffinity() {
        // Currently only distribute affinity for search nodes
        AbstractService.distributeCpuSocketAffinity(cluster.getSearch().getSearchNodes());
    }
Returns indexing cluster implicitly created by this,
or empty if an explicit cluster is used (or if called before the build phase)
config-model/src/main/java/com/yahoo/vespa/model/content/Content.java