/**
* 更新單個(gè)Topic路由信息
*/
public boolean updateTopicRouteInfoFromNameServer(final String topic) {
    return updateTopicRouteInfoFromNameServer(topic, false, null);
}

/**
* 更新單個(gè)Topic路由信息
*/
public boolean updateTopicRouteInfoFromNameServer(final String topic, boolean isDefault,
    DefaultMQProducer defaultMQProducer) {
    try {
        if (this.lockNamesrv.tryLock(LOCK_TIMEOUT_MILLIS, TimeUnit.MILLISECONDS)) {
            try {
                TopicRouteData topicRouteData;
                if (isDefault && defaultMQProducer != null) {
                	// 使用默認(rèn)TopicKey獲取TopicRouteData
                    topicRouteData = this.mQClientAPIImpl.getDefaultTopicRouteInfoFromNameServer(defaultMQProducer.getCreateTopicKey(), 1000 * 3);
                    if (topicRouteData != null) {
                        for (QueueData data : topicRouteData.getQueueDatas()) {
                            int queueNums = Math.min(defaultMQProducer.getDefaultTopicQueueNums(), data.getReadQueueNums());
                            data.setReadQueueNums(queueNums);
                            data.setWriteQueueNums(queueNums);
                        }
                    }
                } else {
                    topicRouteData = this.mQClientAPIImpl.getTopicRouteInfoFromNameServer(topic, 1000 * 3);
                }
                if (topicRouteData != null) {
                    TopicRouteData old = this.topicRouteTable.get(topic);
                    boolean changed = topicRouteDataIsChange(old, topicRouteData);
                    if (!changed) {
                        changed = this.isNeedUpdateTopicRouteInfo(topic);
                    } else {
                        log.info("the topic[{}] route info changed, old[{}] ,new[{}]", topic, old, topicRouteData);
                    }
                    if (changed) {
                    	// 克隆出一個(gè)實(shí)例cloneTopicRouteData ： topicRouteData會(huì)被設(shè)置到下面的publishInfo/subscribeInfo 
                        TopicRouteData cloneTopicRouteData = topicRouteData.cloneTopicRouteData();
						// 更新Broker地址相關(guān)信息，當(dāng)某個(gè)Broker心跳超時(shí)后，會(huì)被從brokerAddrTable中移除
                        for (BrokerData bd : topicRouteData.getBrokerDatas()) {
                            this.brokerAddrTable.put(bd.getBrokerName(), bd.getBrokerAddrs());
                        }
                        // Update Pub info
                        {
                            TopicPublishInfo publishInfo = topicRouteData2TopicPublishInfo(topic, topicRouteData);
                            publishInfo.setHaveTopicRouterInfo(true);
                            Iterator<Entry<String, MQProducerInner>> it = this.producerTable.entrySet().iterator();
                            while (it.hasNext()) {
                                Entry<String, MQProducerInner> entry = it.next();
                                MQProducerInner impl = entry.getValue();
                                if (impl != null) {
                                    impl.updateTopicPublishInfo(topic, publishInfo);
                                }
                            }
                        }
                        // Update sub info
                        {
                            Set<MessageQueue> subscribeInfo = topicRouteData2TopicSubscribeInfo(topic, topicRouteData);
                            Iterator<Entry<String, MQConsumerInner>> it = this.consumerTable.entrySet().iterator();
                            while (it.hasNext()) {
                                Entry<String, MQConsumerInner> entry = it.next();
                                MQConsumerInner impl = entry.getValue();
                                if (impl != null) {
                                    impl.updateTopicSubscribeInfo(topic, subscribeInfo);
                                }
                            }
                        }
                        log.info("topicRouteTable.put. Topic = {}, TopicRouteData[{}]", topic, cloneTopicRouteData);
                        this.topicRouteTable.put(topic, cloneTopicRouteData);
                        return true;
                    }
                } else {
                    log.warn("updateTopicRouteInfoFromNameServer, getTopicRouteInfoFromNameServer return null, Topic: {}. [{}]", topic, this.clientId);
                }
            } catch (MQClientException e) {
                if (!topic.startsWith(MixAll.RETRY_GROUP_TOPIC_PREFIX)) {
                    log.warn("updateTopicRouteInfoFromNameServer Exception", e);
                }
            } catch (RemotingException e) {
                log.error("updateTopicRouteInfoFromNameServer Exception", e);
                throw new IllegalStateException(e);
            } finally {
                this.lockNamesrv.unlock();
            }
        } else {
            log.warn("updateTopicRouteInfoFromNameServer tryLock timeout {}ms. [{}]", LOCK_TIMEOUT_MILLIS, this.clientId);
        }
    } catch (InterruptedException e) {
        log.warn("updateTopicRouteInfoFromNameServer Exception", e);
    }
    return false;
}