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/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*/4static 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* -02-01 11:30:00投递, 设置为: new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").parse("-02-0115* 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: -02-01 11:30:00投递, 设置为: new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").parse("-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 messageString 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/tomj2ee/p/15815186.html
<em> </em>
package org.apache.rocketmq.broker.delay;import ty.channel.ChannelHandlerContext;import mons.lang3.time.DateFormatUtils;import org.apache.rocketmq.broker.BrokerController;import org.mon.protocol.ResponseCode;import org.mon.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 .InetSocketAddress;import .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);}@Overridepublic 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
/tomj2ee/p/15815157.html
开源rocketmq延迟队列实现：
/venus-suite/rocketmq-with-delivery-time.git
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