rocketmq源码剖析之客户端topic路由刷新

rocketmq的client在启动的时候，会通过开启一个定时任务来定期刷新topic信息，这里就来看一下这个刷新的过程。

首先来看一下这个定时任务：

this.scheduledExecutorService.scheduleAtFixedRate(new Runnable() {

    @Override
    public void run() {
        try {
            MQClientInstance.this.updateTopicRouteInfoFromNameServer();
        } catch (Exception e) {
            log.error("ScheduledTask updateTopicRouteInfoFromNameServer exception", e);
        }
    }
}, 10, this.clientConfig.getPollNameServerInterval(), TimeUnit.MILLISECONDS);

从源码可以看见，这个定时任务是在client启动之后延迟10ms执行，并且之后每隔一定时长重复执行，如果没有特定设置，该定时为30s。

/**
 * Pulling topic information interval from the named server
 */
private int pollNameServerInterval = 1000 * 30;

在执行刷新topic信息的操作中，其首先是从生产者和消费者两个注册表中获取到topic信息，然后再迭代更新。

public void updateTopicRouteInfoFromNameServer() {
    Set<String> topicList = new HashSet<String>();

    // Consumer
    {
        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) {
                Set<SubscriptionData> subList = impl.subscriptions();
                if (subList != null) {
                    for (SubscriptionData subData : subList) {
                        topicList.add(subData.getTopic());
                    }
                }
            }
        }
    }

    // Producer
    {
        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) {
                Set<String> lst = impl.getPublishTopicList();
                topicList.addAll(lst);
            }
        }
    }

    for (String topic : topicList) {
        this.updateTopicRouteInfoFromNameServer(topic);
    }
}

在更新方面，首先是从远程（namesrv）获取到最新的topic数据，然后再更新。执行更新操作后，对对新老数据进行比较来判断是否需要更新发布订阅的信息，如果需要则去更新。具体源码如下所示：

public boolean updateTopicRouteInfoFromNameServer(final String topic) {
    // 不指定默认的producer
    return updateTopicRouteInfoFromNameServer(topic, false, null);
}

public boolean updateTopicRouteInfoFromNameServer(final String topic, boolean isDefault,
    DefaultMQProducer defaultMQProducer) {
    try {
        // 可重入锁
        if (this.lockNamesrv.tryLock(LOCK_TIMEOUT_MILLIS, TimeUnit.MILLISECONDS)) {
            try {
                TopicRouteData topicRouteData;
                if (isDefault && defaultMQProducer != null) {
                    // 如果指定了默认的producer，则获取指定的topic信息
                    topicRouteData = this.mQClientAPIImpl.getDefaultTopicRouteInfoFromNameServer(defaultMQProducer.getCreateTopicKey(),
                        1000 * 3);
                    // 如果获取到topic信息则设置队列数
                    if (topicRouteData != null) {
                        for (QueueData data : topicRouteData.getQueueDatas()) {
                            int queueNums = Math.min(defaultMQProducer.getDefaultTopicQueueNums(), data.getReadQueueNums());
                            data.setReadQueueNums(queueNums);
                            data.setWriteQueueNums(queueNums);
                        }
                    }
                } else {
                    // 根据给定topic从namesrv获取数据
                    topicRouteData = this.mQClientAPIImpl.getTopicRouteInfoFromNameServer(topic, 1000 * 3);
                }
                if (topicRouteData != null) {
                    TopicRouteData old = this.topicRouteTable.get(topic);
                    // 判断topic信息是否变化
                    boolean changed = topicRouteDataIsChange(old, topicRouteData);
                    if (!changed) {
                        // 如果没有变化则再次判断是否需要更新，如果当前的没有发布队列，则会进行更新
                        changed = this.isNeedUpdateTopicRouteInfo(topic);
                    } else {
                        log.info("the topic[{}] route info changed, old[{}] ,new[{}]", topic, old, topicRouteData);
                    }

                    // 如果需要更新
                    if (changed) {
                        // 克隆拷贝一份topic数据
                        TopicRouteData cloneTopicRouteData = topicRouteData.cloneTopicRouteData();

                        // 设置broker地址
                        for (BrokerData bd : topicRouteData.getBrokerDatas()) {
                            this.brokerAddrTable.put(bd.getBrokerName(), bd.getBrokerAddrs());
                        }

                        // 更新消息发布者的信息
                        {
                            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);
                                }
                            }
                        }

                        // 更新消息订阅者的信息
                        {
                            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);
                        // 设置topic路由信息
                        this.topicRouteTable.put(topic, cloneTopicRouteData);
                        return true;
                    }
                } else {
                    log.warn("updateTopicRouteInfoFromNameServer, getTopicRouteInfoFromNameServer return null, Topic: {}", topic);
                }
            } catch (Exception e) {
                if (!topic.startsWith(MixAll.RETRY_GROUP_TOPIC_PREFIX) && !topic.equals(MixAll.AUTO_CREATE_TOPIC_KEY_TOPIC)) {
                    log.warn("updateTopicRouteInfoFromNameServer Exception", e);
                }
            } finally {
                this.lockNamesrv.unlock();
            }
        } else {
            log.warn("updateTopicRouteInfoFromNameServer tryLock timeout {}ms", LOCK_TIMEOUT_MILLIS);
        }
    } catch (InterruptedException e) {
        log.warn("updateTopicRouteInfoFromNameServer Exception", e);
    }

    return false;
}