Message Queuing (D) --- RocketMQ- message 2

Outline

  Then we continue on an analysis messaging, talked about the festival may encounter situations broker fails before the message is sent, RocketMQ mainly used two strategies:

• Retry sending
• broker failure delay mechanism when the latter refers to a failure of a broker, the broker will temporarily excluded in the message queue of the selected range, and then reaches the point in time continues to retry sending, when the transmission time of consumption long the more, the more so when the long delay (as caching algorithms, the use of the less, the easier it is to eliminate). Here broker failure delay mechanism

LatencyFaultToleranceImpl

接着昨天选取某一个消息队列的代码 

    / ** 
     * Broker fault delay mechanism 
     * acquired, determines whether the failure, failure of the shift register recording 
     * 
     * / 
    public selectOneMessageQueue the MessageQueue (Final TopicPublishInfo tpInfo, Final String lastBrokerName) { 
        IF (this.sendLatencyFaultEnable) { 
            the try { 
                // the same thread , index increases. 1 
                int index = tpInfo.getSendWhichQueue () getAndIncrement ();. 
                for (int I = 0; I <tpInfo.getMessageQueueList () size ();. I ++) { 
                    // modulo the same threads to send different MessageQueue 
                    int the Math.abs POS = (index ++)% tpInfo.getMessageQueueList () size ();. 
                    IF (POS <0) 
                        POS = 0;
                    MessageQueue mq = tpInfo.getMessageQueueList().get(pos);
                    //判断该 broker 是否失效
                    if (latencyFaultTolerance.isAvailable(mq.getBrokerName())) {
                        if (null == lastBrokerName || mq.getBrokerName().equals(lastBrokerName))
                            return mq;
                    }
                }
                // 获取的 mq 失效
                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);
            }

            return tpInfo.selectOneMessageQueue();
        }

        return tpInfo.selectOneMessageQueue(lastBrokerName);
    }

broker 故障延迟机制相关类如下

其中LatencyFaultToleranceImpl 定义内部类 FaultItem ，从名字也可以看出这是放置失效broker用的，内部存放 currentLatency表示延时时间，startTimestamp 表示失效时间终点时间戳。

    // LatencyFaultToleranceImpl#updateFaultItem 

    @Override
    /**
     *
     * @param name broker名字
     * @param currentLatency 当前延迟时长
     * @param notAvailableDuration 延迟时长
     */
    @Override
    public void updateFaultItem(final String name, final long currentLatency, final long notAvailableDuration) {
        FaultItem old = this.faultItemTable.get(name);
        if (null == old) {
            final FaultItem faultItem = new FaultItem(name);
            faultItem.setCurrentLatency(currentLatency);
            //可以看到 下次可用的时间 =  现在的时间 + 延迟的时间
            faultItem.setStartTimestamp(System.currentTimeMillis() + notAvailableDuration);

            old = this.faultItemTable.putIfAbsent(name, faultItem);
            if (old != null) {
                old.setCurrentLatency(currentLatency);
                old.setStartTimestamp(System.currentTimeMillis() + notAvailableDuration);
            }
        } else {
            old.setCurrentLatency(currentLatency);
            old.setStartTimestamp(System.currentTimeMillis() + notAvailableDuration);
        }
    }


    /**
     * 尝试从规避的broker 中选择一个可用的较好的 broker ,如果没找到，将返回 null
     * 哪一个较好呢？ 肯定是规避时间较短的
     */
    @Override
    public String pickOneAtLeast() {
        final Enumeration<FaultItem> elements = this.faultItemTable.elements();
        List<FaultItem> tmpList = new LinkedList<FaultItem>();
        while (elements.hasMoreElements()) {
            final FaultItem faultItem = elements.nextElement();
            tmpList.add(faultItem);
        }

        if (!tmpList.isEmpty()) {
            //洗牌后又排序,这里看不懂为啥要洗牌后排序，为什么不直接排序？
            Collections.shuffle(tmpList);
            //排序的根据看 FaultItem 的 compareTo 方法，根据时间排序
            Collections.sort(tmpList);

            final int half = tmpList.size() / 2;
            if (half <= 0) {
                return tmpList.get(0).getName();
            } else {
                // whichItemWorst 记录本次选取的 broker ,加若选去后还是发送失败，那么同个线程下次再次调用 pickOneAtLeast 的时候
                //就会调用选用另外一个broker
                final int i = this.whichItemWorst.getAndIncrement() % half;
                return tmpList.get(i).getName();
            }
        }

        return null;
    }

    // MQFaultStrategy#updateFaultItem
    // 其中 currentLatency 是发送时长（发送花了多少时间）
    public void updateFaultItem(final String brokerName, final long currentLatency, boolean isolation) {
        if (this.sendLatencyFaultEnable) {
            long duration = computeNotAvailableDuration(isolation ? 30000 : currentLatency);
            this.latencyFaultTolerance.updateFaultItem(brokerName, currentLatency, duration);
        }
    }

    //计算出需要延迟的时长
    private long computeNotAvailableDuration(final long currentLatency) {
        for (int i = latencyMax.length - 1; i >= 0; i--) {
            if (currentLatency >= latencyMax[i])
                return this.notAvailableDuration[i];
        }

        return 0;
    }


    private long[] latencyMax = {50L, 100L, 550L, 1000L, 2000L, 3000L, 15000L};
    private long[] notAvailableDuration = {0L, 0L, 30000L, 60000L, 120000L, 180000L, 600000L};

消息发送核心方法

  假如是一个异步发送方法

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

        DefaultMQProducer producer = new DefaultMQProducer("Jodie_Daily_test");
        producer.start();
        producer.setRetryTimesWhenSendAsyncFailed(0);

        for (int i = 0; i < 10000000; i++) {
            try {
                final int index = i;
                Message msg = new Message("Jodie_topic_1023",
                    "TagA",
                    "OrderID188",
                    "Hello world".getBytes(RemotingHelper.DEFAULT_CHARSET));
                producer.send(msg, new SendCallback() {
                    @Override
                    public void onSuccess(SendResult sendResult) {
                        System.out.printf("%-10d OK %s %n", index, sendResult.getMsgId());
                    }

                    @Override
                    public void onException(Throwable e) {
                        System.out.printf("%-10d Exception %s %n", index, e);
                        e.printStackTrace();
                    }
                });
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        producer.shutdown();
    }

DefaultMQProducerimpl#sendKernelImpl是消息发送的核心方法，我们看一下

    /**
     *
     * @param msg 发送的消息
     * @param mq  选定的消息队列
     * @param communicationMode 交互模式
     * @param sendCallback  异步消息 callback 回调
     * @param topicPublishInfo topic消息
     * @param timeout 超时时长
     * @return
     * @throws MQClientException
     * @throws RemotingException
     * @throws MQBrokerException
     * @throws InterruptedException
     */
    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 {
        //No.1 获取地址
        String brokerAddr = this.mQClientFactory.findBrokerAddressInPublish(mq.getBrokerName());
        if (null == brokerAddr) {
            tryToFindTopicPublishInfo(mq.getTopic());
            brokerAddr = this.mQClientFactory.findBrokerAddressInPublish(mq.getBrokerName());
        }

        SendMessageContext context = null;
        if (brokerAddr != null) {
            //
            brokerAddr = MixAll.brokerVIPChannel(this.defaultMQProducer.isSendMessageWithVIPChannel(), brokerAddr);

            byte[] prevBody = msg.getBody();
            try {
                //for MessageBatch,ID has been set in the generating process
                // 为消息分配全局唯一 ID ,如果消息体默认超过 4K ,会对消息采用 zip 压缩，设置标识位
                if (!(msg instanceof MessageBatch)) {
                    MessageClientIDSetter.setUniqID(msg);
                }

                int sysFlag = 0;
                if (this.tryToCompressMessage(msg)) {
                    sysFlag |= MessageSysFlag.COMPRESSED_FLAG;
                }

                final String tranMsg = msg.getProperty(MessageConst.PROPERTY_TRANSACTION_PREPARED);
                if (tranMsg != null && Boolean.parseBoolean(tranMsg)) {
                    sysFlag |= MessageSysFlag.TRANSACTION_PREPARED_TYPE;
                }

                // 如果有钩子函数，执行钩子函数
                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);
                }

                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);
                }

                //==================== 构造request请求体 ==================
                
                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;

                //==================== 构造request请求体 ==================

                //（重要）根据不同的交互模式，发送请求，核心发送逻辑
                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:
                        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;
                ....
                ....
                (异常处理)

    }           

底层发送

  MQ 客户端发送消息的入口是 MQClientAPIImpl#sendMessage，MQClientAPIImpl 持有 RemotingClient 字段，它是个接口，实现类是 NettyRemotingClient ，即是它就是真正执行发送的对象，请求命令是 RequestCode.SEND_MESSAGE，我们可以找到该命令的处理类： org . apache.rocketmq. broker.processor.SendMessageProcessor。人口方法在 SendMessageProcessor#sendMessage。

    //SendMessageProcessor#sendMessage 

    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);
        // No.1 先检查
        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);
        // 如果消息重试次数超过允许的最大重试次数，消息将进入DLD延迟队列
        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;
            }
        }

        //（重要）进行消息存储，后续分析
        PutMessageResult putMessageResult = this.brokerController.getMessageStore().putMessage(msgInner);

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

    }

    //

    protected RemotingCommand msgCheck(final ChannelHandlerContext ctx,
        final SendMessageRequestHeader requestHeader, final RemotingCommand response) {
        // 检查是否可写
        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;
        }
        // 检查该Topic是否可以进行消息发送
        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;
        }

        //在 NameServer端存储主题的配置信息
        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;
            }
        }
        // 检查队列，如果队列不合法，返回错误码
        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;
    }

to sum up

  Send logic we can summarize

1. Creating DefaultProducer, started its start method
2. send method call, using internal DefaultProducer the DefaultProducerImpl perform transmission operation, MQClient perform transmission DefaultProducerImpl use, which the middle of a broker failure delay transmission mechanism, finally to MQClientAPIImpl transmission method, MQClientAPIImpl using RemotingClient transmission command, the message inspection, and finally to DefaultMessageStore #putMessage for message storage. Another one, we know brokerController and NamerServerController two classes that store a variety of important information so that messages sent to other modules and other modules (as long as the module is held controller) can be a variety of methods to get the message. At the same time through the class interface design, function expansion package in an abstract class, but do not hold the actual use and ultimately, interface classes are being held, to facilitate the expansion later in the design.

Reference material

• "RocketMQ Inside"