void dispose() {
            final String partitionPath = ProducerZooKeeper.this.metaZookeeper.brokerTopicsPubPath + "/" + this.topic;
            ProducerZooKeeper.this.zkClient.unsubscribeChildChanges(partitionPath, this);
        }
called when broker list changed.

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