@JsonIgnore
    public boolean isConfigServerHost() {
        return isHostedVespaApplicationWithPredicate(ApplicationInstanceId::isConfigServerHost) &&
                Objects.equals(clusterId, ClusterId.CONFIG_SERVER_HOST) &&
                Objects.equals(serviceType, ServiceType.HOST_ADMIN);
    }
Is a config server (and not controller!)
application-model/src/main/java/com/yahoo/vespa/applicationmodel/ServiceCluster.java