rocketmq实现延迟队列精确到秒级实现（总结编）

前言篇：

　　为了节约成本，决定通过自研来改造rocketmq，添加任意时间延迟的延时队列，开源版本的rocketmq只有支持18个等级的延迟时间，

其实对于大部分的功能是够用了的，但是以前的项目，全部都是使用了阿里云的rocketmq，原因是不同的供应商的订单的延时时间是不同的

（部分供应商的订单未支付30分钟取消，有些1个半小时取消，各种时间都有），

所以使用了大量的延时队列，但是开源版本不支持任意时间延时（希望官方支持这个功能）

为了实现这个功能，网上查询了不少资料，查询到不少相关的文章，主要实现都是基于时间轮来实现的，

但是比较少开源的代码实现（也许大家都没有这个需求吧）

debug实践篇：

1. 撸起袖子加油干，首先，下载源代码 https://github.com/apache/rocketmq.git，导入ide

运行mvn  package 生成jar包，如果成功的话，会生成到distribution目录下面

2. 查看文档，发现要运行namesvr 和 broker

找到 src\main\java\org\apache\rocketmq\namesrv\NamesrvStartup.java ，开心的执行main方法，

哦哦哦哦哦，果然报错了，提示 rocketmq.home.dir 目录不存在，查看源码, 原来是从system.propeties读取的，

为了调试，我毫不犹豫的加上了配置文件，

再次运行，不报错了，控制台显示，成功啦（生活是多么美好，空气是多么清晰！）

3.运行 broker ，打开 src\main\java\org\apache\rocketmq\broker\BrokerStartup.java，执行main方法，

添加 配置文件 （D:\\mq\\rocketmq-rocketmq-all-4.9.2是我本地的路径，你要修改成自己的）

1 System.setProperty("rocketmq.home.dir", "D:\\mq\\rocketmq-rocketmq-all-4.9.2\\rb");
2 System.setProperty("user.home", "D:\\mq\\rocketmq-rocketmq-all-4.9.2\\rb\\home\\");

运行一下，成功了，开心的发一条消息，试试，哦哦哦哦哦。发不出去哦（人生最痛苦的事情是，快要成功了，却没有成功）。

原来还要配置namesvr地址，在启动命令，添加 -n   localhost:9876   ( 上面的namesvr 启动的ip和端口)

4.漫长的改造之路 （我们是勇敢的斯巴达勇士，一直勇往直前）

用了阿里云的延时队列，发现它的message 可以传一个时间过来（任意的延时时间）

来来来，我们复制一下（不要告诉别人，我们一直是复制，粘贴的，没有原创， 嘘 ......）

 1     /**
 2      * 该类预定义一些系统键.
 3      */
 4     static public class SystemPropKey {
 5         public static final String TAG = "__TAG";
 6         public static final String KEY = "__KEY";
 7         public static final String MSGID = "__MSGID";
 8         public static final String SHARDINGKEY = "__SHARDINGKEY";
 9         public static final String RECONSUMETIMES = "__RECONSUMETIMES";
10         public static final String BORNTIMESTAMP = "__BORNTIMESTAMP";
11         public static final String BORNHOST = "__BORNHOST";
12         /**
13          * 设置消息的定时投递时间（绝对时间). <p>例1: 延迟投递, 延迟3s投递, 设置为: System.currentTimeMillis() + 3000; <p>例2: 定时投递,
14          * 2016-02-01 11:30:00投递, 设置为: new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").parse("2016-02-01
15          * 11:30:00").getTime()
16          */
17         public static final String STARTDELIVERTIME = "__STARTDELIVERTIME";
18     }

/**
     * <p> 设置消息的定时投递时间（绝对时间),最大延迟时间为7天. </p> <ol> <li>延迟投递: 延迟3s投递, 设置为: System.currentTimeMillis() + 3000;</li>
     * <li>定时投递: 2016-02-01 11:30:00投递, 设置为: new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").parse("2016-02-01
     * 11:30:00").getTime()</li> </ol>
     */
    public void setStartDeliverTime(final long value) {
        putSystemProperties(SystemPropKey.STARTDELIVERTIME, String.valueOf(value));
    }

5.既然要改造rocketmq，在哪里改呢，debug，debug，debug（一直到天荒地老），功夫不负有心人，找到啦，

找到  \src\main\java\org\apache\rocketmq\broker\processor\SendMessageProcessor.java， 发现

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;
        }
    }

继续debug，发现 sendMessage 就是处理发送消息的，

如果我们在这里判断是否延时消息就写入文件，然后返回成功到客户端，等到了时间就发送延迟消息，不就搞定了吗？

oh，yes，就是这么干的

        //处理延迟消息 delay message

        String startTime = msgInner.getProperty(Message.SystemPropKey.STARTDELIVERTIME);
        boolean isDelayMsg = false;
        long nextStartTime = 0;
        if (startTime != null && msgInner.getDelayTimeLevel() <= 0) {
            nextStartTime = Long.parseLong(startTime);
            if (nextStartTime >= System.currentTimeMillis()) {
                isDelayMsg = true;
            }
        }
        if (isDelayMsg) {
            return delayProcessor.handlePutMessageResultFuture(response, request, msgInner, ctx, queueIdInt, nextStartTime);
        } else {
            if (traFlag != null && Boolean.parseBoolean(traFlag)) {
                if (this.brokerController.getBrokerConfig().isRejectTransactionMessage()) {
                    response.setCode(ResponseCode.NO_PERMISSION);
                    response.setRemark(
                            "the broker[" + this.brokerController.getBrokerConfig().getBrokerIP1()
                                    + "] sending transaction message is forbidden");
                    return response;
                }
                putMessageResult = this.brokerController.getTransactionalMessageService().prepareMessage(msgInner);
            } else {
                putMessageResult = this.brokerController.getMessageStore().putMessage(msgInner);
            }

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

        }
    }

其中 delayProcessor.handlePutMessageResultFuture 是我们用来处理延迟消息的地方

我们按照每个时间一个文件夹来保存延时消息，等延时消息到达后，定时的写入延时队列里面。

详细原理，请查考 rocketmq 原理实现篇 https://www.cnblogs.com/tomj2ee/p/15815186.html

package org.apache.rocketmq.broker.delay;

import io.netty.channel.ChannelHandlerContext;
import org.apache.commons.lang3.time.DateFormatUtils;
import org.apache.rocketmq.broker.BrokerController;
import org.apache.rocketmq.common.protocol.ResponseCode;
import org.apache.rocketmq.common.protocol.header.SendMessageResponseHeader;
import org.apache.rocketmq.logging.InternalLogger;
import org.apache.rocketmq.logging.InternalLoggerFactory;
import org.apache.rocketmq.remoting.protocol.RemotingCommand;
import org.apache.rocketmq.store.MessageExtBrokerInner;

import java.io.*;
import java.net.InetSocketAddress;
import java.net.SocketAddress;
import java.util.Date;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.ThreadLocalRandom;

public class DelayProcessor implements  Runnable {

    protected static final InternalLogger log = InternalLoggerFactory.getLogger(DelayProcessor.class.getCanonicalName());

    protected final BrokerController brokerController;
    protected final SocketAddress storeHost;

    private ExecutorService jobTaskExecute = Executors.newFixedThreadPool(16);

    public DelayProcessor(final BrokerController brokerController) {
        this.brokerController = brokerController;
        this.storeHost = new InetSocketAddress(brokerController.getBrokerConfig().getBrokerIP1(), brokerController
                .getNettyServerConfig().getListenPort());
        Thread thread = new Thread(this);
        thread.setName("delayProcessor-run---thread");

        thread.setDaemon(true);
        new File(getDelayPath()).mkdirs();
        thread.start();
        Thread missCallThread = new Thread(() -> {
            try {
                for(;;) {
                    Thread.sleep(10 * 1000);
                    sendMissCallMsg();
                }
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        });
        missCallThread.setName("delayProcessor-callback-thread");
        missCallThread.start();
        System.out.println("init delay success " +getDelayPath());

    }

    public RemotingCommand handlePutMessageResultFuture(RemotingCommand response,
                                                        RemotingCommand request,
                                                        MessageExtBrokerInner msgInner,
                                                        ChannelHandlerContext ctx,
                                                        int queueIdInt, long nextStartTime) {
        return handlePutMessageResult(response, request, msgInner, ctx, queueIdInt, nextStartTime);

    }

    private RemotingCommand handlePutMessageResult(RemotingCommand response,
                                                   RemotingCommand request, MessageExtBrokerInner msg,
                                                   ChannelHandlerContext ctx,
                                                   int queueIdInt, long nextStartTime) {
        boolean svOk = saveMsgFile(nextStartTime, msg);
        SendMessageResponseHeader sendMessageResponseHeader = new SendMessageResponseHeader();
        sendMessageResponseHeader.setQueueId(1);
        sendMessageResponseHeader.setMsgId("0");
        sendMessageResponseHeader.setQueueOffset(0l);
        sendMessageResponseHeader.setTransactionId("");
        RemotingCommand newCommand = RemotingCommand.createRequestCommand(ResponseCode.SUCCESS, sendMessageResponseHeader);

        if (svOk) {
            newCommand.setCode(ResponseCode.SUCCESS);
        } else {
            newCommand.setCode(ResponseCode.SYSTEM_ERROR);
            newCommand.setRemark("发送消息延迟失败！");
        }
        newCommand.setExtFields(request.getExtFields());
        newCommand.setVersion(response.getVersion());
        newCommand.setOpaque(response.getOpaque());
        newCommand.setLanguage(response.getLanguage());
        newCommand.setBody(request.getBody());

        if (!request.isOnewayRPC()) {
            try {
                ctx.writeAndFlush(newCommand);
            } catch (Throwable e) {
                log.error("DelayProcessor process request over, but response failed", e);
                log.error(request.toString());
                log.error(response.toString());
            }
        }
        return newCommand;
    }

    public void putMessage(MessageExtBrokerInner msgInner) {
        this.brokerController.getMessageStore().putMessage(msgInner);
    }

    @Override
    public void run() {
        for (; ; ) {
            long curTime = System.currentTimeMillis() / 1000;
            jobTaskExecute.submit(() -> sendMsg(curTime));
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {

            }
        }
    }

    private String getDelayPath() {
        String delayPath = "./delay-store"+ File.separator + "delay";
        return delayPath;
    }

    private boolean saveMsgFile(long startTime, MessageExtBrokerInner msgInner) {

        ObjectOutputStream objectOutputStream = null;
        try {
            String msgId =(startTime/1000 )+"-"+ System.currentTimeMillis() + "-" + ThreadLocalRandom.current().nextInt(99999999);
            System.out.println( getCurrentTime()+"写入延迟消息 >>" + msgId);
            String parentDir = getDelayPath() + File.separator + startTime / 1000;
            File parentFile = new File(parentDir);
            if (!parentFile.exists()) {
                parentFile.mkdirs();
            }
            String fileName = parentDir + File.separator + msgId;

            FileOutputStream fos = new FileOutputStream(fileName);
            BufferedOutputStream bos = new BufferedOutputStream(fos);
            objectOutputStream = new ObjectOutputStream(bos);
            objectOutputStream.writeObject(msgInner);
            return true;
        } catch (Exception ex) {
            log.error("saveMsgFile ex:", ex);
            return false;
        } finally {
            try {
                if (objectOutputStream != null) {
                    objectOutputStream.close();
                }
            } catch (Exception ex) {
                log.error("saveMsgFile ex:", ex);
            }
        }

    }

    private MessageExtBrokerInner readFile(File f) {
        ObjectInputStream ois = null;
        try {
            ois = new ObjectInputStream(new FileInputStream(f));
            return (MessageExtBrokerInner) ois.readObject();
        } catch (Exception ex) {
            return null;
        } finally {
            if (ois != null) {
                try {
                    ois.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    private  void sendMissCallMsg() {
        File lst = new File(getDelayPath());
        File[] files = lst.listFiles();
        long startTime = System.currentTimeMillis() / 1000 - 10 * 1000;
        for (File f : files) {
            String name = f.getName();
            if (f.isDirectory() && !name.equals(".") && !name.equals("..")) {
                try {
                    Long fileTime = Long.parseLong(name);
                    if (fileTime <= startTime) {
                        sendMsg(fileTime);
                    }
                } catch (Exception ex) {
                }
            }
        }

    }

    private String  getCurrentTime(){
       return  Thread.currentThread().getName()+ ">>["+DateFormatUtils.format(new Date(), "yyyy-MM-dd HH:mm:ss")+"] ";
    }
    private void sendMsg(long startTime) {
        File lst = new File(getDelayPath() + File.separator + startTime);
        File[] files = lst.listFiles();
        if (files != null) {
            for (File f : files) {
                System.out.println( getCurrentTime()+"时间到发送>> "+ startTime+" to commitLog " + f.getName());
                MessageExtBrokerInner msgInner = readFile(f);
                if (msgInner != null) {
                    putMessage(msgInner);
                    System.out.println( getCurrentTime()+"写入log >> "+ startTime+" to commitLog " + f.getName()+" success");
                    f.delete();
                }
            }
            lst.delete();
        }
    }
}

总结：rocketmq延迟队列实现主要是通过时间轮和文件来保存延时消息，等到了时间后，再写入延时队列，来达到延时的目的。

总共有4种方式来实现延时队列，可以参考延时队列的实现原理篇

https://www.cnblogs.com/tomj2ee/p/15815157.html