RocketMQ-发送消息

消息发送与接收整体流程图

作者：数齐
链接：https://www.jianshu.com/p/464e558ae398
来源：简书
简书著作权归作者所有，任何形式的转载都请联系作者获得授权并注明出处

Producer发送消息局部时序图

发送消息

测试用例

public class Producer {
    public static void main(String[] args) throws MQClientException {
        DefaultMQProducer producer = new DefaultMQProducer("ProducerGroupName");
        producer.setNamesrvAddr("localhost:9876");
        producer.start();

        for (int i = 0; i < 100; i++){
            try {
                Message msg = new Message("TopicTest8",
                        "TagA",
                        "Hello world".getBytes(RemotingHelper.DEFAULT_CHARSET));
                SendResult sendResult = producer.send(msg);
                System.out.println(sendResult);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        producer.shutdown();
    }
}

具体的实现是在org.apache.rocketmq.client.impl.producer.DefaultMQProducerImpl#sendDefaultImpl

private SendResult sendDefaultImpl(
        Message msg,
        final CommunicationMode communicationMode,
        final SendCallback sendCallback,
        final long timeout
    ) throws MQClientException, RemotingException, MQBrokerException, InterruptedException {
        this.makeSureStateOK();
        Validators.checkMessage(msg, this.defaultMQProducer);

        final long invokeID = random.nextLong();
        long beginTimestampFirst = System.currentTimeMillis();
        long beginTimestampPrev = beginTimestampFirst;
        long endTimestamp = beginTimestampFirst;
        //根据topic获取路由对象
        TopicPublishInfo topicPublishInfo = this.tryToFindTopicPublishInfo(msg.getTopic());
        if (topicPublishInfo != null && topicPublishInfo.ok()) {
            boolean callTimeout = false;
            MessageQueue mq = null;
            Exception exception = null;
            SendResult sendResult = null;
            int timesTotal = communicationMode == CommunicationMode.SYNC ? 1 + this.defaultMQProducer.getRetryTimesWhenSendFailed() : 1;
            int times = 0;
            String[] brokersSent = new String[timesTotal];
            for (; times < timesTotal; times++) {
                String lastBrokerName = null == mq ? null : mq.getBrokerName();
                //负载均衡，这个topic对应好多个队列，但只挑选一个
                MessageQueue mqSelected = this.selectOneMessageQueue(topicPublishInfo, lastBrokerName);
                if (mqSelected != null) {
                    mq = mqSelected;
                    brokersSent[times] = mq.getBrokerName();
                    try {
                        beginTimestampPrev = System.currentTimeMillis();
                        if (times > 0) {
                            //Reset topic with namespace during resend.
                            msg.setTopic(this.defaultMQProducer.withNamespace(msg.getTopic()));
                        }
                        long costTime = beginTimestampPrev - beginTimestampFirst;
                        if (timeout < costTime) {
                            callTimeout = true;
                            break;
                        }

                        //真正的发送
                        sendResult = this.sendKernelImpl(msg, mq, communicationMode, sendCallback, topicPublishInfo, timeout - costTime);
                        endTimestamp = System.currentTimeMillis();
                        this.updateFaultItem(mq.getBrokerName(), endTimestamp - beginTimestampPrev, false);
                        switch (communicationMode) {
                            case ASYNC:
                                return null;
                            case ONEWAY:
                                return null;
                            case SYNC:
                                if (sendResult.getSendStatus() != SendStatus.SEND_OK) {
                                    if (this.defaultMQProducer.isRetryAnotherBrokerWhenNotStoreOK()) {
                                        continue;
                                    }
                                }

                                return sendResult;
                            default:
                                break;
                        }
                    } catch (RemotingException e) {
                        endTimestamp = System.currentTimeMillis();
                        this.updateFaultItem(mq.getBrokerName(), endTimestamp - beginTimestampPrev, true);
                        log.warn(String.format("sendKernelImpl exception, resend at once, InvokeID: %s, RT: %sms, Broker: %s", invokeID, endTimestamp - beginTimestampPrev, mq), e);
                        log.warn(msg.toString());
                        exception = e;
                        continue;
                    } catch (MQClientException e) {
                        endTimestamp = System.currentTimeMillis();
                        this.updateFaultItem(mq.getBrokerName(), endTimestamp - beginTimestampPrev, true);
                        log.warn(String.format("sendKernelImpl exception, resend at once, InvokeID: %s, RT: %sms, Broker: %s", invokeID, endTimestamp - beginTimestampPrev, mq), e);
                        log.warn(msg.toString());
                        exception = e;
                        continue;
                    } catch (MQBrokerException e) {
                        endTimestamp = System.currentTimeMillis();
                        this.updateFaultItem(mq.getBrokerName(), endTimestamp - beginTimestampPrev, true);
                        log.warn(String.format("sendKernelImpl exception, resend at once, InvokeID: %s, RT: %sms, Broker: %s", invokeID, endTimestamp - beginTimestampPrev, mq), e);
                        log.warn(msg.toString());
                        exception = e;
                        switch (e.getResponseCode()) {
                            case ResponseCode.TOPIC_NOT_EXIST:
                            case ResponseCode.SERVICE_NOT_AVAILABLE:
                            case ResponseCode.SYSTEM_ERROR:
                            case ResponseCode.NO_PERMISSION:
                            case ResponseCode.NO_BUYER_ID:
                            case ResponseCode.NOT_IN_CURRENT_UNIT:
                                continue;
                            default:
                                if (sendResult != null) {
                                    return sendResult;
                                }

                                throw e;
                        }
                    } catch (InterruptedException e) {
                        endTimestamp = System.currentTimeMillis();
                        this.updateFaultItem(mq.getBrokerName(), endTimestamp - beginTimestampPrev, false);
                        log.warn(String.format("sendKernelImpl exception, throw exception, InvokeID: %s, RT: %sms, Broker: %s", invokeID, endTimestamp - beginTimestampPrev, mq), e);
                        log.warn(msg.toString());

                        log.warn("sendKernelImpl exception", e);
                        log.warn(msg.toString());
                        throw e;
                    }
                } else {
                    break;
                }
            }

            if (sendResult != null) {
                return sendResult;
            }

            String info = String.format("Send [%d] times, still failed, cost [%d]ms, Topic: %s, BrokersSent: %s",
                times,
                System.currentTimeMillis() - beginTimestampFirst,
                msg.getTopic(),
                Arrays.toString(brokersSent));

            info += FAQUrl.suggestTodo(FAQUrl.SEND_MSG_FAILED);

            MQClientException mqClientException = new MQClientException(info, exception);
            if (callTimeout) {
                throw new RemotingTooMuchRequestException("sendDefaultImpl call timeout");
            }

            if (exception instanceof MQBrokerException) {
                mqClientException.setResponseCode(((MQBrokerException) exception).getResponseCode());
            } else if (exception instanceof RemotingConnectException) {
                mqClientException.setResponseCode(ClientErrorCode.CONNECT_BROKER_EXCEPTION);
            } else if (exception instanceof RemotingTimeoutException) {
                mqClientException.setResponseCode(ClientErrorCode.ACCESS_BROKER_TIMEOUT);
            } else if (exception instanceof MQClientException) {
                mqClientException.setResponseCode(ClientErrorCode.BROKER_NOT_EXIST_EXCEPTION);
            }

            throw mqClientException;
        }
        //找到NameServer的列表
        List nsList = this.getmQClientFactory().getMQClientAPIImpl().getNameServerAddressList();
        if (null == nsList || nsList.isEmpty()) {
            throw new MQClientException(
                "No name server address, please set it." + FAQUrl.suggestTodo(FAQUrl.NAME_SERVER_ADDR_NOT_EXIST_URL), null).setResponseCode(ClientErrorCode.NO_NAME_SERVER_EXCEPTION);
        }

        throw new MQClientException("No route info of this topic, " + msg.getTopic() + FAQUrl.suggestTodo(FAQUrl.NO_TOPIC_ROUTE_INFO),
            null).setResponseCode(ClientErrorCode.NOT_FOUND_TOPIC_EXCEPTION);
    }

如何获取路由表的org.apache.rocketmq.client.impl.producer.DefaultMQProducerImpl#tryToFindTopicPublishInfo

    private TopicPublishInfo tryToFindTopicPublishInfo(final String topic) {
        //从缓存中取数据
        TopicPublishInfo topicPublishInfo = this.topicPublishInfoTable.get(topic);
        if (null == topicPublishInfo || !topicPublishInfo.ok()) {
            //不存在就添加
            this.topicPublishInfoTable.putIfAbsent(topic, new TopicPublishInfo());
           //添加完了，在这里进行从nameServer获取数据进行更新，比如说队列数
            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;
        }
    }

先从缓存中获取TopicPublishInfo类型的路由信息，如果是第一次缓存中肯定是没有的，就往topicPublishInfoTable（ConcurrentMap）中塞入一个新创建的对象也就是this.topicPublishInfoTable.putIfAbsent(topic, new TopicPublishInfo()),我们看到在代码块了又从缓存中获取数据，所以我们可以得出this.mQClientFactory.updateTopicRouteInfoFromNameServer(topic)这个方法做的事情应该是：从namesrv中获取Topic的数据，然后封装成TopicPublishInfo类型的对数放置到topicPublishInfoTable中进行缓存。具体是不是这样呢，我们继续看,最终进入的代码是

org.apache.rocketmq.client.impl.factory.MQClientInstance#updateTopicRouteInfoFromNameServer(java.lang.String, boolean, org.apache.rocketmq.client.producer.DefaultMQProducer)

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) {
                        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 {
                        //获取路由的数据
                        topicRouteData = this.mQClientAPIImpl.getTopicRouteInfoFromNameServer(topic, 1000 * 3);
                    }
                    if (topicRouteData != null) {
                        //从缓存中获取到老的路由的信息
                        TopicRouteData old = this.topicRouteTable.get(topic);
                        //比较一下是否发生了变化
                        boolean changed = topicRouteDataIsChange(old, topicRouteData);
                        if (!changed) {
                            /*如果未发生改变就运行下面的参数，
                            判断判断生产者和消费者是否可用，
                            如果不可用，也算修改了，
                            也就是changed=true
                            * */
                            changed = this.isNeedUpdateTopicRouteInfo(topic);
                        } else {
                            log.info("the topic[{}] route info changed, old[{}] ,new[{}]", topic, old, topicRouteData);
                        }

                        if (changed) {
                            //不使用原来的信息，复制数据
                            TopicRouteData cloneTopicRouteData = topicRouteData.cloneTopicRouteData();

                            for (BrokerData bd : topicRouteData.getBrokerDatas()) {
                                //设置broker的名字与地址信息
                                this.brokerAddrTable.put(bd.getBrokerName(), bd.getBrokerAddrs());
                            }

                            // Update Pub info
                            {
                                //更新TopicPublishInfo中的数据
                                TopicPublishInfo publishInfo = topicRouteData2TopicPublishInfo(topic, topicRouteData);
                                //设置有topic的路由的信息
                                publishInfo.setHaveTopicRouterInfo(true);
                                Iterator> it = this.producerTable.entrySet().iterator();
                                while (it.hasNext()) {
                                    Entry entry = it.next();
                                    MQProducerInner impl = entry.getValue();
                                    if (impl != null) {
                                        //更新product的路由信息等
                                        impl.updateTopicPublishInfo(topic, publishInfo);
                                    }
                                }
                            }

                            // Update sub info
                            {
                                Set subscribeInfo = topicRouteData2TopicSubscribeInfo(topic, topicRouteData);
                                Iterator> it = this.consumerTable.entrySet().iterator();
                                while (it.hasNext()) {
                                    Entry entry = it.next();
                                    MQConsumerInner impl = entry.getValue();
                                    if (impl != null) {
                                        //更新consumer的路由信息等
                                        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;
    }

首先是根据入参中的isDefault和defaultMQProducer是否符合获取默认topic配置的条件，如果isDefault为true并且defaultMQProducer不为空的话，就回去默认的Topic：TBW102的配置，首先说一下，这个Topic是系统自带的，当broker启动的时候会将这个Topic的配置同步到namesrv，所以namesrv中一定是有这个信息的。获取到这个配置后再填充QueueData中读写队列的个数。当然如果不符合isDefault和defaultMQProducer的限制，那么就直接根据传入的Topic去namesrv拉取该Topic的配置。假如说我们这个Topic是新创建的，那么namesrv中肯定没有这个信息，所以返回null，如果不是第一次的话，是能查到的，返回的就是这个Topic的配置，如果能查到，那么就存储缓存，里面有一个和老数据比对的过程，然后根据数据。这个方法所做的事情就是这么多。我们返回到我们的执行逻辑中，也就是我们上面tryToFindTopicPublishInfo方法中的操作，先根据传入的Topic到namesrv中回去数据，如果获取不到，那么在用默认的Topic去获取并填充数据，放入缓存。不管怎样，现在缓存中的路由信息是肯定存在的。好了，到目前为止，我们已经有了该Topic的配置了。我们之前没有看过这个TopicPublishInfo类型数据的组成，现在我们看下

public class TopicPublishInfo {
    private boolean orderTopic = false;
    private boolean haveTopicRouterInfo = false;
    private List messageQueueList = new ArrayList();
    private volatile ThreadLocalIndex sendWhichQueue = new ThreadLocalIndex();
    private TopicRouteData topicRouteData;
    ....
    }

里面最核心的部分就是messageQueueList,看下MessageQueue

public class MessageQueue implements Comparable, Serializable {
    private static final long serialVersionUID = 6191200464116433425L;
    private String topic;
    private String brokerName;
    private int queueId;
    ...
    }

定消息要发送到哪个broker中的哪个队列中。下面就是要确定这一点，我们再返回org.apache.rocketmq.client.impl.producer.DefaultMQProducerImpl#sendDefaultImpl现在已经确定了路由表，下面我们需要选出一个消息队列来发送数据，也就是确定一个MessageQueue.也就是MessageQueue tmpmq = this.selectOneMessageQueue(topicPublishInfo, lastBrokerName);在这里也不做累述，通过负载均衡算法选出一个MessageQueue。现在我们有了要发送的数据，另外我们也有了要发送的具体的地点，所以我们现在可以执行发送了。

org.apache.rocketmq.client.impl.MQClientAPIImpl#sendMessage(java.lang.String, java.lang.String, 
org.apache.rocketmq.common.message.Message, 
org.apache.rocketmq.common.protocol.header.SendMessageRequestHeader, long, 
org.apache.rocketmq.client.impl.CommunicationMode, 
org.apache.rocketmq.client.producer.SendCallback, 
org.apache.rocketmq.client.impl.producer.TopicPublishInfo, 
org.apache.rocketmq.client.impl.factory.MQClientInstance, int, 
org.apache.rocketmq.client.hook.SendMessageContext, 
org.apache.rocketmq.client.impl.producer.DefaultMQProducerImpl)

 public SendResult sendMessage(
        final String addr,
        final String brokerName,
        final Message msg,
        final SendMessageRequestHeader requestHeader,
        final long timeoutMillis,
        final CommunicationMode communicationMode,
        final SendCallback sendCallback,
        final TopicPublishInfo topicPublishInfo,
        final MQClientInstance instance,
        final int retryTimesWhenSendFailed,
        final SendMessageContext context,
        final DefaultMQProducerImpl producer
    ) throws RemotingException, MQBrokerException, InterruptedException {
        long beginStartTime = System.currentTimeMillis();
        RemotingCommand request = null;
        if (sendSmartMsg || msg instanceof MessageBatch) {
            SendMessageRequestHeaderV2 requestHeaderV2 = SendMessageRequestHeaderV2.createSendMessageRequestHeaderV2(requestHeader);
           //拼接request
            request = RemotingCommand.createRequestCommand(msg instanceof MessageBatch ? RequestCode.SEND_BATCH_MESSAGE : RequestCode.SEND_MESSAGE_V2, requestHeaderV2);
        } else {
            request = RemotingCommand.createRequestCommand(RequestCode.SEND_MESSAGE, requestHeader);
        }
        //设置请求体
        request.setBody(msg.getBody());

        switch (communicationMode) {
            case ONEWAY:
                //单向请求，不需要返回值
                this.remotingClient.invokeOneway(addr, request, timeoutMillis);
                return null;
            case ASYNC:
                final AtomicInteger times = new AtomicInteger();
                long costTimeAsync = System.currentTimeMillis() - beginStartTime;
                if (timeoutMillis < costTimeAsync) {
                    throw new RemotingTooMuchRequestException("sendMessage call timeout");
                }
                this.sendMessageAsync(addr, brokerName, msg, timeoutMillis - costTimeAsync, request, sendCallback, topicPublishInfo, instance,
                    retryTimesWhenSendFailed, times, context, producer);
                return null;
            case SYNC:
                long costTimeSync = System.currentTimeMillis() - beginStartTime;
                if (timeoutMillis < costTimeSync) {
                    throw new RemotingTooMuchRequestException("sendMessage call timeout");
                }
                return this.sendMessageSync(addr, brokerName, msg, timeoutMillis - costTimeSync, request);
            default:
                assert false;
                break;
        }

        return null;
    }

经过上一步的封装业务数据，到了这里就是封装发送的数据，MQ组件之间的通信遵循统一的协议，就是通过RemotingCommand来实现的，表明这是一个发送信息的请求（RequestCode.SEND_MESSAGE），有了broker的地址，就可以将数据发送给broker进行处理。

Broker如何处理发送过来的数据

Broker在启动的时候，注册了很多数据的解析器。

org.apache.rocketmq.broker.BrokerController#registerProcessor

/**
     * 注册处理器
     */
    public void registerProcessor() {
        /**
         * SendMessageProcessor
         */
        SendMessageProcessor sendProcessor = new SendMessageProcessor(this);
        sendProcessor.registerSendMessageHook(sendMessageHookList);
        sendProcessor.registerConsumeMessageHook(consumeMessageHookList);

        this.remotingServer.registerProcessor(RequestCode.SEND_MESSAGE, sendProcessor, this.sendMessageExecutor);
        this.remotingServer.registerProcessor(RequestCode.SEND_MESSAGE_V2, sendProcessor, this.sendMessageExecutor);
        this.remotingServer.registerProcessor(RequestCode.SEND_BATCH_MESSAGE, sendProcessor, this.sendMessageExecutor);
        this.remotingServer.registerProcessor(RequestCode.CONSUMER_SEND_MSG_BACK, sendProcessor, this.sendMessageExecutor);
        this.fastRemotingServer.registerProcessor(RequestCode.SEND_MESSAGE, sendProcessor, this.sendMessageExecutor);
        this.fastRemotingServer.registerProcessor(RequestCode.SEND_MESSAGE_V2, sendProcessor, this.sendMessageExecutor);
        this.fastRemotingServer.registerProcessor(RequestCode.SEND_BATCH_MESSAGE, sendProcessor, this.sendMessageExecutor);
        this.fastRemotingServer.registerProcessor(RequestCode.CONSUMER_SEND_MSG_BACK, sendProcessor, this.sendMessageExecutor);
        /**
         * PullMessageProcessor
         */
        this.remotingServer.registerProcessor(RequestCode.PULL_MESSAGE, this.pullMessageProcessor, this.pullMessageExecutor);
        this.pullMessageProcessor.registerConsumeMessageHook(consumeMessageHookList);

        /**
         * QueryMessageProcessor
         */
        NettyRequestProcessor queryProcessor = new QueryMessageProcessor(this);
        this.remotingServer.registerProcessor(RequestCode.QUERY_MESSAGE, queryProcessor, this.queryMessageExecutor);
        this.remotingServer.registerProcessor(RequestCode.VIEW_MESSAGE_BY_ID, queryProcessor, this.queryMessageExecutor);

        this.fastRemotingServer.registerProcessor(RequestCode.QUERY_MESSAGE, queryProcessor, this.queryMessageExecutor);
        this.fastRemotingServer.registerProcessor(RequestCode.VIEW_MESSAGE_BY_ID, queryProcessor, this.queryMessageExecutor);

        /**
         * ClientManageProcessor
         */
        ClientManageProcessor clientProcessor = new ClientManageProcessor(this);
        this.remotingServer.registerProcessor(RequestCode.HEART_BEAT, clientProcessor, this.heartbeatExecutor);
        this.remotingServer.registerProcessor(RequestCode.UNREGISTER_CLIENT, clientProcessor, this.clientManageExecutor);
        this.remotingServer.registerProcessor(RequestCode.CHECK_CLIENT_CONFIG, clientProcessor, this.clientManageExecutor);

        this.fastRemotingServer.registerProcessor(RequestCode.HEART_BEAT, clientProcessor, this.heartbeatExecutor);
        this.fastRemotingServer.registerProcessor(RequestCode.UNREGISTER_CLIENT, clientProcessor, this.clientManageExecutor);
        this.fastRemotingServer.registerProcessor(RequestCode.CHECK_CLIENT_CONFIG, clientProcessor, this.clientManageExecutor);

        /**
         * ConsumerManageProcessor
         */
        ConsumerManageProcessor consumerManageProcessor = new ConsumerManageProcessor(this);
        this.remotingServer.registerProcessor(RequestCode.GET_CONSUMER_LIST_BY_GROUP, consumerManageProcessor, this.consumerManageExecutor);
        this.remotingServer.registerProcessor(RequestCode.UPDATE_CONSUMER_OFFSET, consumerManageProcessor, this.consumerManageExecutor);
        this.remotingServer.registerProcessor(RequestCode.QUERY_CONSUMER_OFFSET, consumerManageProcessor, this.consumerManageExecutor);

        this.fastRemotingServer.registerProcessor(RequestCode.GET_CONSUMER_LIST_BY_GROUP, consumerManageProcessor, this.consumerManageExecutor);
        this.fastRemotingServer.registerProcessor(RequestCode.UPDATE_CONSUMER_OFFSET, consumerManageProcessor, this.consumerManageExecutor);
        this.fastRemotingServer.registerProcessor(RequestCode.QUERY_CONSUMER_OFFSET, consumerManageProcessor, this.consumerManageExecutor);

        /**
         * EndTransactionProcessor
         */
        this.remotingServer.registerProcessor(RequestCode.END_TRANSACTION, new EndTransactionProcessor(this), this.endTransactionExecutor);
        this.fastRemotingServer.registerProcessor(RequestCode.END_TRANSACTION, new EndTransactionProcessor(this), this.endTransactionExecutor);

        /**
         * Default
         */
        AdminBrokerProcessor adminProcessor = new AdminBrokerProcessor(this);
        this.remotingServer.registerDefaultProcessor(adminProcessor, this.adminBrokerExecutor);
        this.fastRemotingServer.registerDefaultProcessor(adminProcessor, this.adminBrokerExecutor);
    }

我们可以看到，当请求码是RequestCode.SEND_MESSAGE的时候，他的处理器是SendMessageProcessor
下面我们看下，这个Processor是如何处理这类请求的

org.apache.rocketmq.broker.processor.SendMessageProcessor#processRequest

 @Override
    public RemotingCommand processRequest(ChannelHandlerContext ctx,
                                          RemotingCommand request) throws RemotingCommandException {
        SendMessageContext mqtraceContext;
        switch (request.getCode()) {
            case RequestCode.CONSUMER_SEND_MSG_BACK:
                return this.consumerSendMsgBack(ctx, request);
            default:
                SendMessageRequestHeader requestHeader = parseRequestHeader(request);
                if (requestHeader == null) {
                    return null;
                }

                mqtraceContext = buildMsgContext(ctx, requestHeader);
                this.executeSendMessageHookBefore(ctx, request, mqtraceContext);

                RemotingCommand response;
                if (requestHeader.isBatch()) {
                    response = this.sendBatchMessage(ctx, request, mqtraceContext, requestHeader);
                } else {
                    response = this.sendMessage(ctx, request, mqtraceContext, requestHeader);
                }

                this.executeSendMessageHookAfter(response, mqtraceContext);
                return response;
        }
    }

首先解析得到RequestHeader，另外创建消息上下文mqtraceContext，随后调用回调this.executeSendMessageHookBefore,然后判断发送过来的消息是单条还是批量的，然后分别处理，最后执行回调this.executeSendMessageHookAfter,我们实例中传递过来的数据是单条的，所以看下org.apache.rocketmq.broker.processor.SendMessageProcessor#sendMessage的实现。

private RemotingCommand sendMessage(final ChannelHandlerContext ctx,
        final RemotingCommand request,
        final SendMessageContext sendMessageContext,
        final SendMessageRequestHeader requestHeader) throws RemotingCommandException {

        final RemotingCommand response = RemotingCommand.createResponseCommand(SendMessageResponseHeader.class);
        final SendMessageResponseHeader responseHeader = (SendMessageResponseHeader) response.readCustomHeader();

        response.setOpaque(request.getOpaque());

        response.addExtField(MessageConst.PROPERTY_MSG_REGION, this.brokerController.getBrokerConfig().getRegionId());
        response.addExtField(MessageConst.PROPERTY_TRACE_SWITCH, String.valueOf(this.brokerController.getBrokerConfig().isTraceOn()));

        log.debug("receive SendMessage request command, {}", request);

        final long startTimstamp = this.brokerController.getBrokerConfig().getStartAcceptSendRequestTimeStamp();
        if (this.brokerController.getMessageStore().now() < startTimstamp) {
            response.setCode(ResponseCode.SYSTEM_ERROR);
            response.setRemark(String.format("broker unable to service, until %s", UtilAll.timeMillisToHumanString2(startTimstamp)));
            return response;
        }

        response.setCode(-1);
        //这里面会将topic的数据持久化，然后注册到nameserver
        //关注点2
        super.msgCheck(ctx, requestHeader, response);
        if (response.getCode() != -1) {
            return response;
        }

        final byte[] body = request.getBody();

        int queueIdInt = requestHeader.getQueueId();
        TopicConfig topicConfig = this.brokerController.getTopicConfigManager().selectTopicConfig(requestHeader.getTopic());

        if (queueIdInt < 0) {
            queueIdInt = Math.abs(this.random.nextInt() % 99999999) % topicConfig.getWriteQueueNums();
        }

        MessageExtBrokerInner msgInner = new MessageExtBrokerInner();
        msgInner.setTopic(requestHeader.getTopic());
        msgInner.setQueueId(queueIdInt);

        if (!handleRetryAndDLQ(requestHeader, response, request, msgInner, topicConfig)) {
            return response;
        }

        msgInner.setBody(body);
        msgInner.setFlag(requestHeader.getFlag());
        MessageAccessor.setProperties(msgInner, MessageDecoder.string2messageProperties(requestHeader.getProperties()));
        msgInner.setPropertiesString(requestHeader.getProperties());
        msgInner.setBornTimestamp(requestHeader.getBornTimestamp());
        msgInner.setBornHost(ctx.channel().remoteAddress());
        msgInner.setStoreHost(this.getStoreHost());
        msgInner.setReconsumeTimes(requestHeader.getReconsumeTimes() == null ? 0 : requestHeader.getReconsumeTimes());

        if (this.brokerController.getBrokerConfig().isRejectTransactionMessage()) {
            String traFlag = msgInner.getProperty(MessageConst.PROPERTY_TRANSACTION_PREPARED);
            if (traFlag != null) {
                response.setCode(ResponseCode.NO_PERMISSION);
                response.setRemark(
                    "the broker[" + this.brokerController.getBrokerConfig().getBrokerIP1() + "] sending transaction message is forbidden");
                return response;
            }
        }

        //关注点3
        PutMessageResult putMessageResult = this.brokerController.getMessageStore().putMessage(msgInner);

        return handlePutMessageResult(putMessageResult, response, request, msgInner, responseHeader, sendMessageContext, ctx, queueIdInt);

    }

首先我们看下关注点2，是一个check,为啥要单独拎出来说，是因为这里面有个重要的步骤就是：创建新的topic的步骤

protected RemotingCommand msgCheck(final ChannelHandlerContext ctx,
        final SendMessageRequestHeader requestHeader, final RemotingCommand response) {
        if (!PermName.isWriteable(this.brokerController.getBrokerConfig().getBrokerPermission())
            && this.brokerController.getTopicConfigManager().isOrderTopic(requestHeader.getTopic())) {
            response.setCode(ResponseCode.NO_PERMISSION);
            response.setRemark("the broker[" + this.brokerController.getBrokerConfig().getBrokerIP1()
                + "] sending message is forbidden");
            return response;
        }
        if (!this.brokerController.getTopicConfigManager().isTopicCanSendMessage(requestHeader.getTopic())) {
            String errorMsg = "the topic[" + requestHeader.getTopic() + "] is conflict with system reserved words.";
            log.warn(errorMsg);
            response.setCode(ResponseCode.SYSTEM_ERROR);
            response.setRemark(errorMsg);
            return response;
        }

        TopicConfig topicConfig =
            this.brokerController.getTopicConfigManager().selectTopicConfig(requestHeader.getTopic());
        if (null == topicConfig) {
            int topicSysFlag = 0;
            if (requestHeader.isUnitMode()) {
                if (requestHeader.getTopic().startsWith(MixAll.RETRY_GROUP_TOPIC_PREFIX)) {
                    topicSysFlag = TopicSysFlag.buildSysFlag(false, true);
                } else {
                    topicSysFlag = TopicSysFlag.buildSysFlag(true, false);
                }
            }

            log.warn("the topic {} not exist, producer: {}", requestHeader.getTopic(), ctx.channel().remoteAddress());
            topicConfig = this.brokerController.getTopicConfigManager().createTopicInSendMessageMethod(
                requestHeader.getTopic(),
                requestHeader.getDefaultTopic(),
                RemotingHelper.parseChannelRemoteAddr(ctx.channel()),
                requestHeader.getDefaultTopicQueueNums(), topicSysFlag);

            if (null == topicConfig) {
                if (requestHeader.getTopic().startsWith(MixAll.RETRY_GROUP_TOPIC_PREFIX)) {
                    topicConfig =
                        this.brokerController.getTopicConfigManager().createTopicInSendMessageBackMethod(
                            requestHeader.getTopic(), 1, PermName.PERM_WRITE | PermName.PERM_READ,
                            topicSysFlag);
                }
            }

            if (null == topicConfig) {
                response.setCode(ResponseCode.TOPIC_NOT_EXIST);
                response.setRemark("topic[" + requestHeader.getTopic() + "] not exist, apply first please!"
                    + FAQUrl.suggestTodo(FAQUrl.APPLY_TOPIC_URL));
                return response;
            }
        }

        int queueIdInt = requestHeader.getQueueId();
        int idValid = Math.max(topicConfig.getWriteQueueNums(), topicConfig.getReadQueueNums());
        if (queueIdInt >= idValid) {
            String errorInfo = String.format("request queueId[%d] is illegal, %s Producer: %s",
                queueIdInt,
                topicConfig.toString(),
                RemotingHelper.parseChannelRemoteAddr(ctx.channel()));

            log.warn(errorInfo);
            response.setCode(ResponseCode.SYSTEM_ERROR);
            response.setRemark(errorInfo);

            return response;
        }
        return response;
    }

这里面会根据传入的Topic的名称查询TopicConfig，也就是TopicConfig topicConfig =this.brokerController.getTopicConfigManager().selectTopicConfig(requestHeader.getTopic()）;因为是新的topic，所以broker本地肯定是没有的，所以需要createTopicInSendMessageMethod

public TopicConfig createTopicInSendMessageMethod(final String topic, final String defaultTopic,
                                                      final String remoteAddress, final int clientDefaultTopicQueueNums, final int topicSysFlag) {
        TopicConfig topicConfig = null;
        boolean createNew = false;

        try {
            if (this.lockTopicConfigTable.tryLock(LOCK_TIMEOUT_MILLIS, TimeUnit.MILLISECONDS)) {
                try {
                    topicConfig = this.topicConfigTable.get(topic);
                    if (topicConfig != null)
                        return topicConfig;

                    TopicConfig defaultTopicConfig = this.topicConfigTable.get(defaultTopic);
                    if (defaultTopicConfig != null) {
                        if (defaultTopic.equals(MixAll.DEFAULT_TOPIC)) {
                            if (!this.brokerController.getBrokerConfig().isAutoCreateTopicEnable()) {
                                defaultTopicConfig.setPerm(PermName.PERM_READ | PermName.PERM_WRITE);
                            }
                        }

                        if (PermName.isInherited(defaultTopicConfig.getPerm())) {
                            topicConfig = new TopicConfig(topic);

                            int queueNums =
                                    clientDefaultTopicQueueNums > defaultTopicConfig.getWriteQueueNums() ? defaultTopicConfig
                                            .getWriteQueueNums() : clientDefaultTopicQueueNums;

                            if (queueNums < 0) {
                                queueNums = 0;
                            }

                            topicConfig.setReadQueueNums(queueNums);
                            topicConfig.setWriteQueueNums(queueNums);
                            int perm = defaultTopicConfig.getPerm();
                            perm &= ~PermName.PERM_INHERIT;
                            topicConfig.setPerm(perm);
                            topicConfig.setTopicSysFlag(topicSysFlag);
                            topicConfig.setTopicFilterType(defaultTopicConfig.getTopicFilterType());
                        } else {
                            log.warn("Create new topic failed, because the default topic[{}] has no perm [{}] producer:[{}]",
                                    defaultTopic, defaultTopicConfig.getPerm(), remoteAddress);
                        }
                    } else {
                        log.warn("Create new topic failed, because the default topic[{}] not exist. producer:[{}]",
                                defaultTopic, remoteAddress);
                    }

                    if (topicConfig != null) {
                        log.info("Create new topic by default topic:[{}] config:[{}] producer:[{}]",
                                defaultTopic, topicConfig, remoteAddress);

                        this.topicConfigTable.put(topic, topicConfig);

                        this.dataVersion.nextVersion();

                        createNew = true;

                        //持久化配置信息到本地
                        this.persist();
                    }
                } finally {
                    this.lockTopicConfigTable.unlock();
                }
            }
        } catch (InterruptedException e) {
            log.error("createTopicInSendMessageMethod exception", e);
        }

        if (createNew) {
            this.brokerController.registerBrokerAll(false, true);
        }

        return topicConfig;
    }

首先根据topic的名称查询本地缓存，如果存在的话，直接返回，如果不存在根据defaultTopic获取默认的Topic的配置来创建一个TopicConfig来添加到本地缓存中，并且将数据持久化到本地，重启的时候就会有这个新创建的数据的信息了，这还不够，还需要同步到namesrv,也就是registerBrokerAll,这样namesrv中也会有新创建的这个Topic的信息了，后续不管是producer还是consumer来拉取topic的配置，都能拉取了。下面我们再看下关注点3，存储数据PutMessageResult putMessageResult = this.brokerController.getMessageStore().putMessage(msgInner);

public PutMessageResult putMessage(MessageExtBrokerInner msg) {
        /**
         * 检查是否shutdown，若是则直接返回服务不可用的错误
         */
        if (this.shutdown) {
            log.warn("message store has shutdown, so putMessage is forbidden");
            return new PutMessageResult(PutMessageStatus.SERVICE_NOT_AVAILABLE, null);
        }
        /**
         * 检查是否为备用Broker，若是则直接返回服务不可用的错误；
         */
        if (BrokerRole.SLAVE == this.messageStoreConfig.getBrokerRole()) {
            long value = this.printTimes.getAndIncrement();
            if ((value % 50000) == 0) {
                log.warn("message store is slave mode, so putMessage is forbidden ");
            }

            return new PutMessageResult(PutMessageStatus.SERVICE_NOT_AVAILABLE, null);
        }
        /**
         * 检查是否有写的权限，若无则直接返回服务不可用的错误；
         */
        if (!this.runningFlags.isWriteable()) {
            long value = this.printTimes.getAndIncrement();
            if ((value % 50000) == 0) {
                log.warn("message store is not writeable, so putMessage is forbidden " + this.runningFlags.getFlagBits());
            }

            return new PutMessageResult(PutMessageStatus.SERVICE_NOT_AVAILABLE, null);
        } else {
            this.printTimes.set(0);
        }
        /**
         * 检查topic的长度是否大于最大值127，若是则返回消息不合法；
         */
        if (msg.getTopic().length() > Byte.MAX_VALUE) {
            log.warn("putMessage message topic length too long " + msg.getTopic().length());
            return new PutMessageResult(PutMessageStatus.MESSAGE_ILLEGAL, null);
        }
        /**
         * 检查peroperties的长度是否大于32767，若是则返回消息不合法；
         */
        if (msg.getPropertiesString() != null && msg.getPropertiesString().length() > Short.MAX_VALUE) {
            log.warn("putMessage message properties length too long " + msg.getPropertiesString().length());
            return new PutMessageResult(PutMessageStatus.PROPERTIES_SIZE_EXCEEDED, null);
        }

        if (this.isOSPageCacheBusy()) {
            return new PutMessageResult(PutMessageStatus.OS_PAGECACHE_BUSY, null);
        }

        long beginTime = this.getSystemClock().now();
        /**
         * 上述检查全部通过之后，调用CommitLog对象的putMessage方法进行消息的写入；
         */
        PutMessageResult result = this.commitLog.putMessage(msg);

        /**
         * 完成消息写入之后，调用StoreStatsService对象进行相关统计工作
         */
        long eclipseTime = this.getSystemClock().now() - beginTime;
        if (eclipseTime > 500) {
            log.warn("putMessage not in lock eclipse time(ms)={}, bodyLength={}", eclipseTime, msg.getBody().length);
        }
        this.storeStatsService.setPutMessageEntireTimeMax(eclipseTime);

        if (null == result || !result.isOk()) {
            this.storeStatsService.getPutMessageFailedTimes().incrementAndGet();
        }

        return result;
    }

可以很明显的看到关键的方法就是PutMessageResult result = this.commitLog.putMessage(msg);将数据存放到CommitLog中,随后告诉producer已经发送成功了。