【RocketMQ源码学习】- 3. Client 发送同步消息

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titleImg

本文较长，代码后面给了方法简图，希望给你帮助

发送的方式

  • 同步发送
  • 异步发送

消息的类型

  • 普通消息
  • 顺序消息
  • 事务消息

发送同步消息的时序图

为了防止读者朋友嫌烦，可以看下时序图，后面我也会给出方法的简图

项目结构如图

源码示例【发送同步消息】

调用DefaultMQProducer.send()发送同步消息

同时需要设置发送的nameSrvAddr\producerGroupName

可以设置发送的超时时间，(默认3s), msgQueueNum(默认4个), 生产端发送异步消息失败重试次数(默认2次)，同步消息无重试次数

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public class Producer {
    public static void main(String[] args) throws MQClientException, InterruptedException {

        DefaultMQProducer producer = new DefaultMQProducer("ProducerGroupName");
        producer.setNamesrvAddr("127.0.0.1:9876");
        producer.setInstanceName("producer1");

        producer.start();

        for (int i = 0; i < 10; i++)
            try {
                {
                    Message msg = new Message("TopicTest",
                        "TagA",
                        "OrderID188",
                            ("Hello world" + i).getBytes(RemotingHelper.DEFAULT_CHARSET));
                    // send方法
                    SendResult sendResult = producer.send(msg);
                    System.out.printf("%s%n", sendResult);
                }

            } catch (Exception e) {
                e.printStackTrace();
            }

        producer.shutdown();
    }
}

步骤三 send方法内部调用sendDefaultImpl()

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private SendResult sendDefaultImpl(
    Message msg,
    final CommunicationMode communicationMode,
    final SendCallback sendCallback,
    final long timeout
    // + 用户来处理异常
) throws MQClientException, RemotingException, MQBrokerException, InterruptedException {
    // + 确保服务状态是RUNNING
    this.makeSureStateOK();
    // + 传参判空
    Validators.checkMessage(msg, this.defaultMQProducer);

    final long invokeID = random.nextLong();
    long beginTimestampFirst = System.currentTimeMillis();
    long beginTimestampPrev = beginTimestampFirst;
    long endTimestamp = beginTimestampFirst;
    /**
     * 根据topic的name,从本地获取tocip信息，如果本地没有就从nameserver中取，同时缓存到本地
     * 包括MessageQueueList, brokeName, topic_name
     */
    TopicPublishInfo topicPublishInfo = this.tryToFindTopicPublishInfo(msg.getTopic());
    if (topicPublishInfo != null && topicPublishInfo.ok()) {
        boolean callTimeout = false;
        MessageQueue mq = null;
        Exception exception = null;
        SendResult sendResult = null;
        /**
         * 生产端的重试：异步方式最大执行次数总共3次，同步1次，
         * 重试针对的是brokeException\MQClientException\RemotingException\返回值失败
         */
        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();
            /** 
             * 根据topic和broke选择1个队列
             * 选择策略，产生一个随机数，hash % broke中队列数，然后hash+1
             * 这个随机数：是线程私有的
             */
            MessageQueue mqSelected = this.selectOneMessageQueue(topicPublishInfo, lastBrokerName);
            if (mqSelected != null) {
                mq = mqSelected;
                // 在重试数组中放入broke_name
                brokersSent[times] = mq.getBrokerName();
                try {
                    beginTimestampPrev = System.currentTimeMillis();
                    if (times > 0) {
                        // Reset topic with namespace during resend.
                        // 重置topic
                        msg.setTopic(this.defaultMQProducer.withNamespace(msg.getTopic()));
                    }
                    // 超时就break，抛出call timeout异常，这时还没有，通过socket重试
                    long costTime = beginTimestampPrev - beginTimestampFirst;
                    if (timeout < costTime) {
                        callTimeout = true;
                        break;
                    }

                    // 【核心，如下】调用sendKernelImpl方法，想选中的messageQueu中投递消息
                    sendResult = this.sendKernelImpl(msg, mq, communicationMode, sendCallback, topicPublishInfo, timeout - costTime);
                    // 获取当前时间，控制所有步骤的时间，不超过用户设置的超时时间，或默认超时时间
                    endTimestamp = System.currentTimeMillis();

                    // 把这个操作时间记录到map中，key=brokerName, value=对象[包括：brokeName, currentLatency当前操作花费时间，startTimestamp开始的时间]
                    this.updateFaultItem(mq.getBrokerName(), endTimestamp - beginTimestampPrev, false);
                    switch (communicationMode) {
                        case ASYNC:
                            return null;
                        case ONEWAY:
                            return null;
                        case SYNC:
                            // 当开启了重试另外一个broke时，才会失败重试
                            if (sendResult.getSendStatus() != SendStatus.SEND_OK) {
                                if (this.defaultMQProducer.isRetryAnotherBrokerWhenNotStoreOK()) {
                                    continue;
                                }
                            }

                            return sendResult;
                        default:
                            break;
                    }
                } catch (RemotingException e) {
                    // 远程调用时异常，会重试
                    endTimestamp = System.currentTimeMillis();
                    // 记录操作时间
                    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();
                    // 记录操作时间
                    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();
                    // 记录操作时间
                    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:          // topic不存在
                        case ResponseCode.SERVICE_NOT_AVAILABLE:    // 服务不可用
                        case ResponseCode.SYSTEM_ERROR:             // 系统错误
                        case ResponseCode.NO_PERMISSION:            // 无权限
                        case ResponseCode.NO_BUYER_ID:              // 
                        case ResponseCode.NOT_IN_CURRENT_UNIT:      // 不在集群中
                            continue;
                        default:
                            if (sendResult != null) {
                                return sendResult;
                            }

                            throw e;
                    }
                } catch (InterruptedException e) {
                    endTimestamp = System.currentTimeMillis();
                    // 记录操作时间
                    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;
    }

    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);
    }

    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);
}

sendDefaultImpl方法简图

步骤四 构建发送参数，使用netty发送消息[sendKernelImpl]

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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 {
    long beginStartTime = System.currentTimeMillis();
    // 获取broker的IP地址，获取到的是主broker
    String brokerAddr = this.mQClientFactory.findBrokerAddressInPublish(mq.getBrokerName());
    if (null == brokerAddr) {
        // 使用topic的name去获取topic，如果本地没有，则在从nameserver中获取，同时也更新broker的信息
        tryToFindTopicPublishInfo(mq.getTopic());
        brokerAddr = this.mQClientFactory.findBrokerAddressInPublish(mq.getBrokerName());
    }

    SendMessageContext context = null;
    if (brokerAddr != null) {
        // 若开启了vipchannel，broke的端口减2
        brokerAddr = MixAll.brokerVIPChannel(this.defaultMQProducer.isSendMessageWithVIPChannel(), brokerAddr);

        byte[] prevBody = msg.getBody();
        try {
            //for MessageBatch,ID has been set in the generating process
            if (!(msg instanceof MessageBatch)) {
                // 设置UNIQ_KEY
                MessageClientIDSetter.setUniqID(msg);
            }

            boolean topicWithNamespace = false;
            if (null != this.mQClientFactory.getClientConfig().getNamespace()) {
                msg.setInstanceId(this.mQClientFactory.getClientConfig().getNamespace());
                topicWithNamespace = true;
            }

            // 尝试压缩消息，有一定的条件，不是MessageBatch，消息超过4k
            int sysFlag = 0;
            boolean msgBodyCompressed = false;
            if (this.tryToCompressMessage(msg)) {
                sysFlag |= MessageSysFlag.COMPRESSED_FLAG;
                msgBodyCompressed = true;
            }

            // 判断是否是事务消息
            final String tranMsg = msg.getProperty(MessageConst.PROPERTY_TRANSACTION_PREPARED);
            if (tranMsg != null && Boolean.parseBoolean(tranMsg)) {
                sysFlag |= MessageSysFlag.TRANSACTION_PREPARED_TYPE;
            }

            // 禁用钩子 todo 疑问待解=>
            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);
            }

            // 发送消息钩子
            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);
                context.setNamespace(this.defaultMQProducer.getNamespace());
                // 事务消息消息类型是半消息
                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);
                }

                 // 记录消息轨迹
                this.executeSendMessageHookBefore(context);
            }

            // 构建请求头
            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);
            // 更新 %RETRY%重试topic里消息的消费时间和 最大消费次数
            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) {
                // 异步
                case ASYNC:
                    Message tmpMessage = msg;
                    boolean messageCloned = false;
                    if (msgBodyCompressed) {
                        //If msg body was compressed, msgbody should be reset using prevBody. 如果消息体被压缩了，应该用prevBody重置msgBody
                        //Clone new message using commpressed message body and recover origin massage. 
                        //Fix bug:https://github.com/apache/rocketmq-externals/issues/66
                        tmpMessage = MessageAccessor.cloneMessage(msg);
                        messageCloned = true;
                        msg.setBody(prevBody);
                    }

                    if (topicWithNamespace) {
                        if (!messageCloned) {
                            tmpMessage = MessageAccessor.cloneMessage(msg);
                            messageCloned = true;
                        }
                        msg.setTopic(NamespaceUtil.withoutNamespace(msg.getTopic(), this.defaultMQProducer.getNamespace()));
                    }

                    // 防止发送之前的处理超时
                    long costTimeAsync = System.currentTimeMillis() - beginStartTime;
                    if (timeout < costTimeAsync) {
                        throw new RemotingTooMuchRequestException("sendKernelImpl call timeout");
                    }

                    // 下面仔细说明这个方法 
                    sendResult = this.mQClientFactory.getMQClientAPIImpl().sendMessage(
                        brokerAddr,
                        mq.getBrokerName(),
                        tmpMessage,
                        requestHeader,
                        timeout - costTimeAsync,
                        communicationMode,
                        sendCallback,
                        topicPublishInfo,
                        this.mQClientFactory,
                        this.defaultMQProducer.getRetryTimesWhenSendAsyncFailed(),
                        context,
                        this);
                    break;
                // 直接发送，不关心发送结果/同步消息
                case ONEWAY:
                case SYNC:
                    // 防止发送之前的处理超时
                    long costTimeSync = System.currentTimeMillis() - beginStartTime;
                    if (timeout < costTimeSync) {
                        throw new RemotingTooMuchRequestException("sendKernelImpl call timeout");
                    }
                    // 下面仔细说明这个方法
                    sendResult = this.mQClientFactory.getMQClientAPIImpl().sendMessage(
                        brokerAddr,
                        mq.getBrokerName(),
                        msg,
                        requestHeader,
                        timeout - costTimeSync,
                        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);
            msg.setTopic(NamespaceUtil.withoutNamespace(msg.getTopic(), this.defaultMQProducer.getNamespace()));
        }
    }

    throw new MQClientException("The broker[" + mq.getBrokerName() + "] not exist", null);
}

方法简图

步骤七 使用netty发送同步消息[invokeSync]

this.mQClientFactory.getMQClientAPIImpl().sendMessage(）

内部调用

  • 异步消息调用的是 NettyRemotingClient.invokeAsync方法
  • 同步消息调用的是 NettyRemotingClient.invokeSync方法

下面跟着代码查看invokeSync方法

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@Override
public RemotingCommand invokeSync(String addr, final RemotingCommand request, long timeoutMillis)
    throws InterruptedException, RemotingConnectException, RemotingSendRequestException, RemotingTimeoutException {
    long beginStartTime = System.currentTimeMillis();
    // 创建channal，如果channel为空，使用 this.bootstrap.connect(RemotingHelper.string2SocketAddress(addr));来创建channel
    final Channel channel = this.getAndCreateChannel(addr);
    // 活跃的channel才能发消息
    if (channel != null && channel.isActive()) {
        try {
            // rpc鉴权
            doBeforeRpcHooks(addr, request);
            long costTime = System.currentTimeMillis() - beginStartTime;
            if (timeoutMillis < costTime) {
                throw new RemotingTimeoutException("invokeSync call timeout");
            }
            // 
            RemotingCommand response = this.invokeSyncImpl(channel, request, timeoutMillis - costTime);
            // 
            doAfterRpcHooks(RemotingHelper.parseChannelRemoteAddr(channel), request, response);
            return response;
        } catch (RemotingSendRequestException e) {
            log.warn("invokeSync: send request exception, so close the channel[{}]", addr);
            this.closeChannel(addr, channel);
            throw e;
        } catch (RemotingTimeoutException e) {
            if (nettyClientConfig.isClientCloseSocketIfTimeout()) {
                this.closeChannel(addr, channel);
                log.warn("invokeSync: close socket because of timeout, {}ms, {}", timeoutMillis, addr);
            }
            log.warn("invokeSync: wait response timeout exception, the channel[{}]", addr);
            throw e;
        }
    } else {
        this.closeChannel(addr, channel);
        throw new RemotingConnectException(addr);
    }
}

方法简图

步骤八 使用netty发送同步消息[invokeSyncImpl]、

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public RemotingCommand invokeSyncImpl(final Channel channel, final RemotingCommand request,
    final long timeoutMillis)
    throws InterruptedException, RemotingSendRequestException, RemotingTimeoutException {
    final int opaque = request.getOpaque();

    try {
        final ResponseFuture responseFuture = new ResponseFuture(channel, opaque, timeoutMillis, null, null);
        this.responseTable.put(opaque, responseFuture);
        final SocketAddress addr = channel.remoteAddress();
        // 使用writeAndFlush发请求，建立返回值的监听，这是netty-client发送消息，还有netty-server收消息
        channel.writeAndFlush(request).addListener(new ChannelFutureListener() {
            @Override
            public void operationComplete(ChannelFuture f) throws Exception {
                if (f.isSuccess()) {
                    responseFuture.setSendRequestOK(true);
                    // 执行成功后return, 跳出这个监听
                    return;
                } else {
                    responseFuture.setSendRequestOK(false);
                }

                responseTable.remove(opaque);
                responseFuture.setCause(f.cause());
                responseFuture.putResponse(null);
                log.warn("send a request command to channel <" + addr + "> failed.");
            }
        });

        // 使用countDownLatch挂起线程，等待收到netty的返回值
        RemotingCommand responseCommand = responseFuture.waitResponse(timeoutMillis);
        // 在clinet的channelRead0将responseCommand赋值，若为空，说明超过一定时间还未获取返回值，这时抛出异常，交由用户处理
        // 可能netty-server收到消息，也有可能没有收到消息，不确定
        if (null == responseCommand) {
            if (responseFuture.isSendRequestOK()) {
                throw new RemotingTimeoutException(RemotingHelper.parseSocketAddressAddr(addr), timeoutMillis,
                    responseFuture.getCause());
            } else {
                throw new RemotingSendRequestException(RemotingHelper.parseSocketAddressAddr(addr), responseFuture.getCause());
            }
        }

        return responseCommand;
    } finally {
        this.responseTable.remove(opaque);
    }
}

方法简图

整体重要步骤

  1. 用send方法发送同步消息
  2. 判断发送service是否处于running状态
  3. 检验发送的参数 如topic是否为空
  4. 根据topicName调用tryToFindTopicPublishInfo方法获取topic详情，里面有这个topic的队列
  5. 选择其中一个队列，选择的策略是：产生一个随机数，hash%brokeSize 然后hash+1, 同时把随机数记录下来，下次还是使用这个随机数
  6. 获取broke的IP地址，如果本地没有，则从nameserver中获取
  7. 如果开启了vipchannel，则端口-2
  8. 尝试压缩消息，消息数不大于4K
  9. 构建消息头
  10. 根据IP创建channel
  11. rpc鉴权
  12. 创建responseFuture, 并把他放到reponseTable中
  13. 使用channel.writeAndFlush发起netty请求，并建立监听
  14. 使用countDownLatch挂起线程，等待收到netty的返回值
  15. 返回结果

结语

刚开始开发送的代码，觉得太长了，不想看了，现在想想他的逻辑挺清晰的，能够帮助你看清别人的开源框架整个构建构成