Settings indexSettings = settingsBuilder().put(_settings)
.put(Esi4JUtils.getSettings(_settings, "index." + indexName + ".", "index."))
.put(Esi4JUtils.getSettings(_settings, "esi4j.index." + indexName + ".", "esi4j.index.")).build();
String clientName = indexSettings.get("esi4j.index.client", DEFAULT_CLIENT);
Esi4JClient client = _clients.get(clientName);
if (client == null) {
// TODO better exception
throw new NullPointerException("client");
}