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 srcmainjavaorgapacherocketmqnamesrvNamesrvStartup.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 srcmainjavaorgapacherocketmqbrokerBrokerStartup.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
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
17 public static final String STARTDELIVERTIME = "__STARTDELIVERTIME";
18 }
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 srcmainjavaorgapacherocketmqbrokerprocessorSendMessageProcessor.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
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//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
1
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。
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