进入RouteInfoManager#pickupTopicRouteData方法

public TopicRouteData pickupTopicRouteData(final String topic) {
    TopicRouteData topicRouteData = new TopicRouteData();
    boolean foundQueueData = false;
    boolean foundBrokerData = false;
    Set<String> brokerNameSet = new HashSet<String>();
    List<BrokerData> brokerDataList = new LinkedList<BrokerData>();
    topicRouteData.setBrokerDatas(brokerDataList);
​
    HashMap<String, List<String>> filterServerMap = new HashMap<String, List<String>>();
    topicRouteData.setFilterServerTable(filterServerMap);
​
    try {
        try {
            //加读锁
            this.lock.readLock().lockInterruptibly();
            //从元数据topicQueueTable中根据topic名字获取队列集合
            List<QueueData> queueDataList = this.topicQueueTable.get(topic);
            if (queueDataList != null) {
                //将获取到的队列集合写入topicRouteData的queueDatas中
                topicRouteData.setQueueDatas(queueDataList);
                foundQueueData = true;
​
                Iterator<QueueData> it = queueDataList.iterator();
                while (it.hasNext()) {
                    QueueData qd = it.next();
                    brokerNameSet.add(qd.getBrokerName());
                }
        //遍历从QueueData集合中提取的brokerName
                for (String brokerName : brokerNameSet) {
                    //根据brokerName从brokerAddrTable获取brokerData
                    BrokerData brokerData = this.brokerAddrTable.get(brokerName);
                    if (null != brokerData) {
                        //克隆brokerData对象，并写入到topicRouteData的brokerDatas中
                        BrokerData brokerDataClone = new BrokerData(brokerData.getCluster(), brokerData.getBrokerName(), (HashMap<Long, String>) brokerData.getBrokerAddrs().clone());
                        brokerDataList.add(brokerDataClone);
                        foundBrokerData = true;
                        //遍历brokerAddrs
                        for (final String brokerAddr : brokerDataClone.getBrokerAddrs().values()) {
                            //根据brokerAddr获取filterServerList，封装后写入到topicRouteData的filterServerTable中
                            List<String> filterServerList = this.filterServerTable.get(brokerAddr);
                            filterServerMap.put(brokerAddr, filterServerList);
                        }
                    }
                }
            }
        } finally {
            //释放读锁
            this.lock.readLock().unlock();
        }
    } catch (Exception e) {
        log.error("pickupTopicRouteData Exception", e);
    }
​
    log.debug("pickupTopicRouteData {} {}", topic, topicRouteData);
​
    if (foundBrokerData && foundQueueData) {
        return topicRouteData;
    }
​
    return null;
}