private MessageStoreFactory<I, Writable, MessageStore<I, Writable>>
createMessageStoreFactory() {
Class<? extends MessageStoreFactory> messageStoreFactoryClass =
MESSAGE_STORE_FACTORY_CLASS.get(conf);
MessageStoreFactory messageStoreFactoryInstance =
ReflectionUtils.newInstance(messageStoreFactoryClass);
messageStoreFactoryInstance.initialize(service, conf);
return messageStoreFactoryInstance;
}