rocketmq producer 高可用原理

rocketmq 分为 namesrv、broker、producer、consumer

broker分为MASTER/SLAVE，对producer而言，会发message到broker上，写只会发送到brokerId=0 主broker上

对consumer而言，是读，既可以是主broker，也可以是备broker

下面来分析一下producer发送message源码过程，以下以顺序消费为例

DefaultMQProducerImpl.sendSelectImpl

其中tryToFindTopicPublishInfo负责查找当前可用的broker

    private SendResult sendSelectImpl(
        Message msg,
        MessageQueueSelector selector,
        Object arg,
        final CommunicationMode communicationMode,
        final SendCallback sendCallback, final long timeout
    ) throws MQClientException, RemotingException, MQBrokerException, InterruptedException {
        long beginStartTime = System.currentTimeMillis();
        this.makeSureStateOK();
        Validators.checkMessage(msg, this.defaultMQProducer);

        TopicPublishInfo topicPublishInfo = this.tryToFindTopicPublishInfo(msg.getTopic());
        if (topicPublishInfo != null && topicPublishInfo.ok()) {
            MessageQueue mq = null;
            try {
                mq = selector.select(topicPublishInfo.getMessageQueueList(), msg, arg);
            } catch (Throwable e) {
                throw new MQClientException("select message queue throwed exception.", e);
            }

            long costTime = System.currentTimeMillis() - beginStartTime;
            if (timeout < costTime) {
                throw new RemotingTooMuchRequestException("sendSelectImpl call timeout");
            }
            if (mq != null) {
                return this.sendKernelImpl(msg, mq, communicationMode, sendCallback, null, timeout - costTime);
            } else {
                throw new MQClientException("select message queue return null.", null);
            }
        }

        throw new MQClientException("No route info for this topic, " + msg.getTopic(), null);
    }

在tryToFindTopicPublishInfo中，调用

1> this.mQClientFactory.updateTopicRouteInfoFromNameServer(topic); 当第一次调用时，NameServer中没有该topic、通过NameServer查topic时是查不到的

2> this.mQClientFactory.updateTopicRouteInfoFromNameServer(topic, true, this.defaultMQProducer); 调用该方法

    private TopicPublishInfo tryToFindTopicPublishInfo(final String topic) {
　　　　　　 //第一次进入时，topicPublishInfoTable中没有该topic的信息
        TopicPublishInfo topicPublishInfo = this.topicPublishInfoTable.get(topic);
        if (null == topicPublishInfo || !topicPublishInfo.ok()) {
            this.topicPublishInfoTable.putIfAbsent(topic, new TopicPublishInfo());
            this.mQClientFactory.updateTopicRouteInfoFromNameServer(topic);
            topicPublishInfo = this.topicPublishInfoTable.get(topic);
        }

        if (topicPublishInfo.isHaveTopicRouterInfo() || topicPublishInfo.ok()) {
            return topicPublishInfo;
        } else {
            this.mQClientFactory.updateTopicRouteInfoFromNameServer(topic, true, this.defaultMQProducer);
            topicPublishInfo = this.topicPublishInfoTable.get(topic);
            return topicPublishInfo;
        }
    }

MQClientInstance.updateTopicRouteInfoFromNameServer(final String topic, boolean isDefault, DefaultMQProducer defaultMQProducer)

这个方法中 isDefault= true, defaultMQProducer!=null时

    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) {//当isDefault=true, defaultMQProducer时会走这个分支
                        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) {
                            TopicRouteData cloneTopicRouteData = topicRouteData.cloneTopicRouteData();

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

                            // Update Pub info
                            {    //在该方法中，过滤到master broker
                                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) {//update topicPublishInfoTable
                                        impl.updateTopicPublishInfo(topic, publishInfo);
                                    }
                                }
                            }

                            // Update sub info
                            {    //拿到readealbe queue
                                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);
                    }
                } 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;
    }

DefaultMQProducerImpl.updateTopicPublishInfo(String, TopicPublishInfo)

该方法中会 更新 DefaultMQProducerImpl.topicPublishInfoTable

@Override
    public void updateTopicPublishInfo(final String topic, final TopicPublishInfo info) {
        if (info != null && topic != null) {
            TopicPublishInfo prev = this.topicPublishInfoTable.put(topic, info);
            if (prev != null) {
                log.info("updateTopicPublishInfo prev is not null, " + prev.toString());
            }
        }
    }

另外，如果某一个broker异常，还有定时任务检查

MQClientInstance.startScheduledTask()

    private void startScheduledTask() {
        if (null == this.clientConfig.getNamesrvAddr()) {
            this.scheduledExecutorService.scheduleAtFixedRate(new Runnable() {

                @Override
                public void run() {
                    try {
                        MQClientInstance.this.mQClientAPIImpl.fetchNameServerAddr();
                    } catch (Exception e) {
                        log.error("ScheduledTask fetchNameServerAddr exception", e);
                    }
                }
            }, 1000 * 10, 1000 * 60 * 2, TimeUnit.MILLISECONDS);
        }

        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);

        this.scheduledExecutorService.scheduleAtFixedRate(new Runnable() {

            @Override
            public void run() {
                try {
                    MQClientInstance.this.cleanOfflineBroker();
                    MQClientInstance.this.sendHeartbeatToAllBrokerWithLock();
                } catch (Exception e) {
                    log.error("ScheduledTask sendHeartbeatToAllBroker exception", e);
                }
            }
        }, 1000, this.clientConfig.getHeartbeatBrokerInterval(), TimeUnit.MILLISECONDS);

        this.scheduledExecutorService.scheduleAtFixedRate(new Runnable() {

            @Override
            public void run() {
                try {
                    MQClientInstance.this.persistAllConsumerOffset();
                } catch (Exception e) {
                    log.error("ScheduledTask persistAllConsumerOffset exception", e);
                }
            }
        }, 1000 * 10, this.clientConfig.getPersistConsumerOffsetInterval(), TimeUnit.MILLISECONDS);

        this.scheduledExecutorService.scheduleAtFixedRate(new Runnable() {

            @Override
            public void run() {
                try {
                    MQClientInstance.this.adjustThreadPool();
                } catch (Exception e) {
                    log.error("ScheduledTask adjustThreadPool exception", e);
                }
            }
        }, 1, 1, TimeUnit.MINUTES);
    }

调用链

　　1. MQClientInstance.updateTopicRouteInfoFromNameServer()

        2.MQClientInstance.updateTopicRouteInfoFromNameServer(String)

        3. MQClientInstance.updateTopicRouteInfoFromNameServer(String, boolean, DefaultMQProducer)

这样就可以最大限度的保证获取到最新的broker

即使这样，还是有可能发送失败，

　　1、因为当定时更新任务30秒内执行完，这时broker也有可能出现问题。会发送失败。

　　2、当失败重试时，MessageQueueSelector.select(List<MessageQueue>, Message, Object)中List<MessageQueue>

list个数会发生变化，对顺序发送来说，会发送到不同的queue中