@edu.umd.cs.findbugs.annotations.SuppressWarnings(value = "DC_DOUBLECHECK")
    private VipAddressResolver getVipAddressResolver() {
        if (vipResolver == null) {
            synchronized (this) {
                if (vipResolver == null) {
                    try {
                        vipResolver = (VipAddressResolver) Class
                                .forName(getOrDefault(CommonClientConfigKey.VipAddressResolverClassName))
                                .newInstance();
                    } catch (InstantiationException | IllegalAccessException | ClassNotFoundException e) {
                        throw new RuntimeException("Cannot instantiate VipAddressResolver", e);
                    }
                }
            }
        }
        return vipResolver;
    }
This class only exists to support code that depends on these constants that are deprecated now that defaults have
moved into the key.
ribbon-core/src/main/java/com/netflix/client/config/AbstractDefaultClientConfigImpl.java