class EtcdDynamicConfiguration implements DynamicConfiguration {

    @Override
    public void addListener(String key, String group, ConfigurationListener listener) {
        if (watchListenerMap.get(listener) == null) {
            EtcdConfigWatcher watcher = new EtcdConfigWatcher(key, group, listener);
            watchListenerMap.put(listener, watcher);
            watcher.watch();
        }
    }

      EtcdDynamicConfiguration(URL url);

}