// GuaranteedUpdate keeps calling 'tryUpdate()' to update key 'key' (of type 'destination')
	// retrying the update until success if there is index conflict.
	// Note that object passed to tryUpdate may change across invocations of tryUpdate() if
	// other writers are simultaneously updating it, so tryUpdate() needs to take into account

	// Prepare ch so that only one update of resolverConfig may
	// run at once.
	conf.ch = make(chan struct{}, 1)
}

// tryUpdate tries to update conf with the named resolv.conf file.
// The name variable only exists for testing. It is otherwise always
// "/etc/resolv.conf".
func (conf *resolverConfig) tryUpdate(name string) {
	conf.initOnce.Do(conf.init)

	if conf.dnsConfig.Load().noReload {
		return
	}

// GuaranteedUpdate implements storage.Interface.GuaranteedUpdate.
func (s *store) GuaranteedUpdate(
	ctx context.Context, key string, destination runtime.Object, ignoreNotFound bool,
	preconditions *storage.Preconditions, tryUpdate storage.UpdateFunc, cachedExistingObject runtime.Object) error {
	preparedKey, err := s.prepareKey(key)
	if err != nil {
		return err
	}
	ctx, span := tracing.Start(ctx, "GuaranteedUpdate etcd3",