if err != nil {
			return err
		}
		updated, _, err := tryUpdate(current, storage.ResponseMeta{ResourceVersion: rev})
		if err != nil {
			return err
		}
		return s.copyInto(updated, destination)
	}
	return s.Storage.GuaranteedUpdate(ctx, key, destination, ignoreNotFound, preconditions, tryUpdate, cachedExistingObject)
}

func (s *DryRunnableStorage) Count(key string) (int64, error) {

	e.lock.Lock()
	defer e.lock.Unlock()

	return e.tryUpdate(func() error {
		return e.alloc.Release(item)
	})

}

func (e *Etcd) ForEach(fn func(int)) {
	e.lock.Lock()
	defer e.lock.Unlock()
	e.alloc.ForEach(fn)
}

// tryUpdate performs a read-update to persist the latest snapshot state of allocation.
func (e *Etcd) tryUpdate(fn func() error) error {

func getSystemNSS() *nssConf {
	nssConfig.tryUpdate()
	nssConfig.mu.Lock()
	conf := nssConfig.nssConf
	nssConfig.mu.Unlock()
	return conf
}

// init initializes conf and is only called via conf.initOnce.
func (conf *nsswitchConfig) init() {
	conf.nssConf = parseNSSConfFile("/etc/nsswitch.conf")
	conf.lastChecked = time.Now()
	conf.ch = make(chan struct{}, 1)
}

// tryUpdate tries to update conf.