public void notifyBrokersChange(String topic) {
        for (final BrokerChangeListener listener : this.getListenerList(topic)) {
            try {
                listener.brokersChanged(topic);
            }
            catch (Exception e) {
                log.error("Notify brokers changed failed", e);
            }
        }
    }
called when broker list changed.

@param topic
metamorphosis-client/src/main/java/com/taobao/metamorphosis/client/producer/ProducerZooKeeper.java