RocketMQ-Producer
为什么学习RocketMQ？很大一部分原因是被官方文档里的这句洗脑了：Apache RocketMQ is a distributed messaging and streaming platform with low latency, high performance and reliability, trillion-level capacity and flexible scalability.注意：是trillion-level。下面解析的主要是RocketMQ中Producer发送同步消息的部分源码(代码部分加上注释后直接从编译器里copy出来的格式多少有些不友好，望大家见谅)
注：转载请注明出处
RocketMQ-Producer发送同步消息流程：消息校验-获取Topic信息-进入发送消息循环-选择发送队列-消息发送(包含很多具体步骤)-检测发送状态-更新Broker延时信息-返回消息发送结果
- 用到的主要方法：
- DefaultMQProducer-send(msg)
- DefaultMQProducerImpl-sendDefaultImpl(msg,communicationMode,sendCallback,timeout)
- DefaultMQProducerImpl-tryToFindTopicPublishInfo(topic)
- MQFaultStrategy-selectOneMessageQueue(tpInfo,lastBrokerName)
- DefaultMQProducerImpl-sendKernelImpl(msg,mq,communicationMode,sendCallback,topicPublishInfo,timeout)
- MQFaultStrategy-updateFaultItem(brokerName,currentLatency,isolation)
具体解析：
- 首先从业务代码里调用RocketMQ的send方法，发送普通消息的话会调用到下面这里
可以看出此时的消息发送是同步发送 - 之后进入到DefaultMQProducerImpl-sendDefaultImpl(msg,communicationMode,sendCallback,timeout)这个方法进行发送消息，具体代码解析如下
private SendResult sendDefaultImpl( Message msg,// 封装好的消息，包括topic，tag，消息内容等信息 final CommunicationMode communicationMode,// 封装后传进来的是SYNC同步发送 final SendCallback sendCallback,// null final long timeout // 默认3000ms ) throws MQClientException, RemotingException, MQBrokerException, InterruptedException { this.makeSureStateOK();// 检测Producer状态是否为RUNNING // 校验消息是否符合规范（校验topic和body各种属性 如是否为空，消息体大小是否过大（最大4M）） Validators.checkMessage(msg, this.defaultMQProducer); final long invokeID = random.nextLong(); long beginTimestampFirst = System.currentTimeMillis(); long beginTimestampPrev = beginTimestampFirst; long endTimestamp = beginTimestampFirst; // 获取Topic信息，详见tryToFindTopicPublishInfo TopicPublishInfo topicPublishInfo = this.tryToFindTopicPublishInfo(msg.getTopic()); if (topicPublishInfo != null && topicPublishInfo.ok()) { MessageQueue mq = null; Exception exception = null; SendResult sendResult = null; // 目测是个三元表达式，既然是同步发送那么timesTotal = 3 int timesTotal = communicationMode == CommunicationMode.SYNC ? 1 + this.defaultMQProducer.getRetryTimesWhenSendFailed() : 1; int times = 0; String[] brokersSent = new String[timesTotal]; // 总共尝试三次发送 for (; times < timesTotal; times++) { String lastBrokerName = null == mq ? null : mq.getBrokerName(); // 选择消息要发送到的队列，有具体解析 MessageQueue mqSelected = this.selectOneMessageQueue(topicPublishInfo, lastBrokerName); if (mqSelected != null) { mq = mqSelected; brokersSent[times] = mq.getBrokerName();// 记录每次消息发送到哪个Broker try { beginTimestampPrev = System.currentTimeMillis(); // 调用发送消息的核心方法 sendResult = this.sendKernelImpl(msg, mq, communicationMode, sendCallback, topicPublishInfo, timeout); endTimestamp = System.currentTimeMillis(); // 更新Broker延时信息 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) {// 更新Broker延时信息，打印出异常，继续循环 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) {// 更新Broker延时信息，打印出异常，继续循环 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) {// 更新Broker延时信息，打印出异常，根据异常情况决定是否继续循环，其余情况直接返回结束循环 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) {// 更新Broker延时信息，打印出异常结束循环 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; } } // 返回消息发送的结果 if (sendResult != null) { return sendResult; } // 异常信息 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 (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; } // NameServer异常 List<String> 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); } // Topic路由信息异常 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); } - 其中调用到DefaultMQProducerImpl-tryToFindTopicPublishInfo(topic)方法获取Topic信息：
private TopicPublishInfo tryToFindTopicPublishInfo(final String topic) { // 从缓存中获取Topic信息，是个ConcurrentMap TopicPublishInfo topicPublishInfo = this.topicPublishInfoTable.get(topic); // 如果没获取到，则去NameServer获取 if (null == topicPublishInfo || !topicPublishInfo.ok()) { this.topicPublishInfoTable.putIfAbsent(topic, new TopicPublishInfo()); // 从NameServer取Topic信息之后会有介绍（此处调用经过封装,后两个参数设为false和null） this.mQClientFactory.updateTopicRouteInfoFromNameServer(topic); topicPublishInfo = this.topicPublishInfoTable.get(topic); } // 检测Topic信息是否可用，可用则返回 if (topicPublishInfo.isHaveTopicRouterInfo() || topicPublishInfo.ok()) { return topicPublishInfo; } else { // 从NameServer取Topic信息，之后会有介绍（此处调用未经封装） this.mQClientFactory.updateTopicRouteInfoFromNameServer(topic, true, this.defaultMQProducer); topicPublishInfo = this.topicPublishInfoTable.get(topic); return topicPublishInfo; } } - 之后调用MQFaultStrategy-selectOneMessageQueue(tpInfo,lastBrokerName)方法获取到要把消息发送到哪个队列：
public MessageQueue selectOneMessageQueue(final TopicPublishInfo tpInfo, final String lastBrokerName) { // 默认情况下为false if (this.sendLatencyFaultEnable) { try { // 如果是第一次发送，lastBrokerName为空，则选择一个可用的Broker中的队列返回 // 如果不是第一次发送，最好的情况是在BrokerName为lastBrokerName且可用的Broker中选择一个队列返回 int index = tpInfo.getSendWhichQueue().getAndIncrement(); for (int i = 0; i < tpInfo.getMessageQueueList().size(); i++) { int pos = Math.abs(index++) % tpInfo.getMessageQueueList().size(); if (pos < 0) pos = 0; MessageQueue mq = tpInfo.getMessageQueueList().get(pos); // 可用的Broker通过一个ConcurrentHashMap维护，key为BrokerName if (latencyFaultTolerance.isAvailable(mq.getBrokerName())) { if (null == lastBrokerName || mq.getBrokerName().equals(lastBrokerName)) return mq; } } // 其次从FaultItemTable选择一个未验证可用性的队列 final String notBestBroker = latencyFaultTolerance.pickOneAtLeast(); int writeQueueNums = tpInfo.getQueueIdByBroker(notBestBroker); if (writeQueueNums > 0) { final MessageQueue mq = tpInfo.selectOneMessageQueue(); if (notBestBroker != null) { mq.setBrokerName(notBestBroker); mq.setQueueId(tpInfo.getSendWhichQueue().getAndIncrement() % writeQueueNums); } return mq; } else { latencyFaultTolerance.remove(notBestBroker); } } catch (Exception e) { log.error("Error occurred when selecting message queue", e); } // 最差的情况随机返回一个队列，未验证队列的可用性 return tpInfo.selectOneMessageQueue(); } // 未开启容错策略 // 第一次发送的话随机选择Broker，重试的时候选择BrokerName != lastBrokerName的Broker中的队列，未验证队列的可用性 return tpInfo.selectOneMessageQueue(lastBrokerName); }未开启容错策略的话直接走最下面return这行代码，开启容错策略的话会有三种情况，最好的情况是选择可用的Broker中的队列 - DefaultMQProducerImpl-sendKernelImpl(msg,mq,communicationMode,sendCallback,topicPublishInfo,timeout)是发送消息的核心方法，同步发送的话包含消息校验-消息发送-校验发送结果流程，代码比较多
private SendResult sendKernelImpl(final Message msg, final MessageQueue mq, final CommunicationMode communicationMode, final SendCallback sendCallback, final TopicPublishInfo topicPublishInfo, final long timeout) throws MQClientException, RemotingException, MQBrokerException, InterruptedException { // 从BrokerAddrTable中获取Broker地址 String brokerAddr = this.mQClientFactory.findBrokerAddressInPublish(mq.getBrokerName()); if (null == brokerAddr) { // tryToFindTopicPublishInfo这个方法有解析 tryToFindTopicPublishInfo(mq.getTopic()); brokerAddr = this.mQClientFactory.findBrokerAddressInPublish(mq.getBrokerName()); } SendMessageContext context = null; if (brokerAddr != null) { // 检测Broker是否使用vip，使用的话返回新的brokerAddr brokerAddr = MixAll.brokerVIPChannel(this.defaultMQProducer.isSendMessageWithVIPChannel(), brokerAddr); byte[] prevBody = msg.getBody();// 消息内容 try { //for MessageBatch,ID has been set in the generating process if (!(msg instanceof MessageBatch)) { MessageClientIDSetter.setUniqID(msg); } int sysFlag = 0; // 消息压缩，把压缩后的消息存在msg的body里，修改sysFlag if (this.tryToCompressMessage(msg)) { sysFlag |= MessageSysFlag.COMPRESSED_FLAG; } //如果属于事物消息，修改sysFlag final String tranMsg = msg.getProperty(MessageConst.PROPERTY_TRANSACTION_PREPARED); if (tranMsg != null && Boolean.parseBoolean(tranMsg)) { sysFlag |= MessageSysFlag.TRANSACTION_PREPARED_TYPE; } // 是否注册了CheckForbiddenHook，若注册了则检查消息否属于禁止消息 if (hasCheckForbiddenHook()) { CheckForbiddenContext checkForbiddenContext = new CheckForbiddenContext(); checkForbiddenContext.setNameSrvAddr(this.defaultMQProducer.getNamesrvAddr()); checkForbiddenContext.setGroup(this.defaultMQProducer.getProducerGroup()); checkForbiddenContext.setCommunicationMode(communicationMode); checkForbiddenContext.setBrokerAddr(brokerAddr); checkForbiddenContext.setMessage(msg); checkForbiddenContext.setMq(mq); checkForbiddenContext.setUnitMode(this.isUnitMode()); this.executeCheckForbiddenHook(checkForbiddenContext); } // 是否注册了sendMessageHookList if (this.hasSendMessageHook()) { context = new SendMessageContext(); context.setProducer(this); context.setProducerGroup(this.defaultMQProducer.getProducerGroup()); context.setCommunicationMode(communicationMode); context.setBornHost(this.defaultMQProducer.getClientIP()); context.setBrokerAddr(brokerAddr); context.setMessage(msg); context.setMq(mq); String isTrans = msg.getProperty(MessageConst.PROPERTY_TRANSACTION_PREPARED); if (isTrans != null && isTrans.equals("true")) { context.setMsgType(MessageType.Trans_Msg_Half); } if (msg.getProperty("__STARTDELIVERTIME") != null || msg.getProperty(MessageConst.PROPERTY_DELAY_TIME_LEVEL) != null) { context.setMsgType(MessageType.Delay_Msg); } this.executeSendMessageHookBefore(context); } // 构建SendMessageRequestHeader对象 SendMessageRequestHeader requestHeader = new SendMessageRequestHeader(); requestHeader.setProducerGroup(this.defaultMQProducer.getProducerGroup()); requestHeader.setTopic(msg.getTopic()); requestHeader.setDefaultTopic(this.defaultMQProducer.getCreateTopicKey()); requestHeader.setDefaultTopicQueueNums(this.defaultMQProducer.getDefaultTopicQueueNums()); requestHeader.setQueueId(mq.getQueueId()); requestHeader.setSysFlag(sysFlag); requestHeader.setBornTimestamp(System.currentTimeMillis()); requestHeader.setFlag(msg.getFlag()); requestHeader.setProperties(MessageDecoder.messageProperties2String(msg.getProperties())); requestHeader.setReconsumeTimes(0); requestHeader.setUnitMode(this.isUnitMode()); requestHeader.setBatch(msg instanceof MessageBatch); if (requestHeader.getTopic().startsWith(MixAll.RETRY_GROUP_TOPIC_PREFIX)) { String reconsumeTimes = MessageAccessor.getReconsumeTime(msg); if (reconsumeTimes != null) { requestHeader.setReconsumeTimes(Integer.valueOf(reconsumeTimes)); MessageAccessor.clearProperty(msg, MessageConst.PROPERTY_RECONSUME_TIME); } String maxReconsumeTimes = MessageAccessor.getMaxReconsumeTimes(msg); if (maxReconsumeTimes != null) { requestHeader.setMaxReconsumeTimes(Integer.valueOf(maxReconsumeTimes)); MessageAccessor.clearProperty(msg, MessageConst.PROPERTY_MAX_RECONSUME_TIMES); } } SendResult sendResult = null; switch (communicationMode) { case ASYNC: sendResult = this.mQClientFactory.getMQClientAPIImpl().sendMessage( brokerAddr, mq.getBrokerName(), msg, requestHeader, timeout, communicationMode, sendCallback, topicPublishInfo, this.mQClientFactory, this.defaultMQProducer.getRetryTimesWhenSendAsyncFailed(), context, this); break; case ONEWAY: case SYNC: // 同步发送消息 // 消息发送完之后会调用MQClientAPIImpl.processSendResponse方法检测发送结果并返回到这里，之后会有详细解析 sendResult = this.mQClientFactory.getMQClientAPIImpl().sendMessage( brokerAddr, mq.getBrokerName(), msg, requestHeader, timeout, communicationMode, context, this); break; default: assert false; break; } if (this.hasSendMessageHook()) { context.setSendResult(sendResult); this.executeSendMessageHookAfter(context); } return sendResult; } catch (RemotingException e) { if (this.hasSendMessageHook()) { context.setException(e); this.executeSendMessageHookAfter(context); } throw e; } catch (MQBrokerException e) { if (this.hasSendMessageHook()) { context.setException(e); this.executeSendMessageHookAfter(context); } throw e; } catch (InterruptedException e) { if (this.hasSendMessageHook()) { context.setException(e); this.executeSendMessageHookAfter(context); } throw e; } finally { msg.setBody(prevBody); } } // 抛出Broker不存在异常 throw new MQClientException("The broker[" + mq.getBrokerName() + "] not exist", null); } - 发送完消息之后还会有一些操作，比如更新Broker延时信息
public void updateFaultItem(final String brokerName, final long currentLatency, boolean isolation) { // 传进来的isolation为false，所以根据currentLatency和latencyMax判断延时情况 if (this.sendLatencyFaultEnable) { // 更新FaultItemTable，当然了sendLatencyFaultEnable目测为false long duration = computeNotAvailableDuration(isolation ? 30000 : currentLatency); this.latencyFaultTolerance.updateFaultItem(brokerName, currentLatency, duration); } } - 返回发送结果SendResult