目錄什么是延時(shí)隊(duì)列，延時(shí)隊(duì)列應(yīng)用于什么場(chǎng)景

延時(shí)隊(duì)列顧名思義，即放置在該隊(duì)列里面的消息是不需要立即消費(fèi)的，而是等待一段時(shí)間之后取出消費(fèi)。那么，為什么需要延遲消費(fèi)呢？我們來(lái)看以下的場(chǎng)景

網(wǎng)上商城下訂單后30分鐘后沒(méi)有完成支付，取消訂單(如：淘寶、去哪兒網(wǎng)) 系統(tǒng)創(chuàng)建了預(yù)約之后，需要在預(yù)約時(shí)間到達(dá)前一小時(shí)提醒被預(yù)約的雙方參會(huì) 系統(tǒng)中的業(yè)務(wù)失敗之后，需要重試

這些場(chǎng)景都非常常見，我們可以思考，比如第二個(gè)需求，系統(tǒng)創(chuàng)建了預(yù)約之后，需要在預(yù)約時(shí)間到達(dá)前一小時(shí)提醒被預(yù)約的雙方參會(huì)。那么一天之中肯定是會(huì)有很多個(gè)預(yù)約的，時(shí)間也是不一定的，假設(shè)現(xiàn)在有1點(diǎn) 2點(diǎn) 3點(diǎn) 三個(gè)預(yù)約，如何讓系統(tǒng)知道在當(dāng)前時(shí)間等于0點(diǎn) 1點(diǎn) 2點(diǎn)給用戶發(fā)送信息呢，是不是需要一個(gè)輪詢，一直去查看所有的預(yù)約，比對(duì)當(dāng)前的系統(tǒng)時(shí)間和預(yù)約提前一小時(shí)的時(shí)間是否相等呢？這樣做非常浪費(fèi)資源而且輪詢的時(shí)間間隔不好控制。如果我們使用延時(shí)消息隊(duì)列呢，我們?cè)趧?chuàng)建時(shí)把需要通知的預(yù)約放入消息中間件中，并且設(shè)置該消息的過(guò)期時(shí)間，等過(guò)期時(shí)間到達(dá)時(shí)再取出消費(fèi)即可。

Rabbitmq實(shí)現(xiàn)延時(shí)隊(duì)列一般而言有兩種形式：第一種方式：利用兩個(gè)特性： Time To Live(TTL)、Dead Letter Exchanges（DLX）第二種方式：利用rabbitmq中的插件x-delay-message

利用TTL DLX實(shí)現(xiàn)延時(shí)隊(duì)列的方式TTL DLX是什么

TTL

RabbitMQ可以針對(duì)隊(duì)列設(shè)置x-expires(則隊(duì)列中所有的消息都有相同的過(guò)期時(shí)間)或者針對(duì)Message設(shè)置x-message-ttl(對(duì)消息進(jìn)行單獨(dú)設(shè)置，每條消息TTL可以不同)，來(lái)控制消息的生存時(shí)間，如果超時(shí)(兩者同時(shí)設(shè)置以最先到期的時(shí)間為準(zhǔn))，則消息變?yōu)閐ead letter(死信)

Dead Letter Exchanges（DLX）RabbitMQ的Queue可以配置x-dead-letter-exchange和x-dead-letter-routing-key（可選）兩個(gè)參數(shù)，如果隊(duì)列內(nèi)出現(xiàn)了dead letter，則按照這兩個(gè)參數(shù)重新路由轉(zhuǎn)發(fā)到指定的隊(duì)列。x-dead-letter-exchange：出現(xiàn)dead letter之后將dead letter重新發(fā)送到指定exchangex-dead-letter-routing-key：出現(xiàn)dead letter之后將dead letter重新按照指定的routing-key發(fā)送

Springboot集成rabbitmq實(shí)現(xiàn)第一種方式

在pom.xml文件中增加rabbitmq的依賴

<dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-amqp</artifactId></dependency>

初始化queue exchange和queue及exchange之間的binding關(guān)系

Config.java

package com.example.demo.deadLetter;import java.util.HashMap;import java.util.Map;import org.springframework.amqp.core.Binding;import org.springframework.amqp.core.BindingBuilder;import org.springframework.amqp.core.DirectExchange;import org.springframework.amqp.core.Queue;import org.springframework.context.annotation.Bean;import org.springframework.context.annotation.Configuration;import com.example.demo.Constants.Constants;@Configurationpublic class Config { // 創(chuàng)建一個(gè)立即消費(fèi)隊(duì)列 @Bean public Queue immediateQueue() {// 第一個(gè)參數(shù)是創(chuàng)建的queue的名字，第二個(gè)參數(shù)是是否支持持久化return new Queue(Constants.IMMEDIATE_QUEUE, true); } // 創(chuàng)建一個(gè)延時(shí)隊(duì)列 @Bean public Queue delayQueue() {Map<String, Object> params = new HashMap<>();// x-dead-letter-exchange 聲明了隊(duì)列里的死信轉(zhuǎn)發(fā)到的DLX名稱，params.put('x-dead-letter-exchange', Constants.IMMEDIATE_EXCHANGE);// x-dead-letter-routing-key 聲明了這些死信在轉(zhuǎn)發(fā)時(shí)攜帶的 routing-key 名稱。params.put('x-dead-letter-routing-key', Constants.IMMEDIATE_ROUTING_KEY);return new Queue(Constants.DELAY_QUEUE, true, false, false, params); } @Bean public DirectExchange immediateExchange() {// 一共有三種構(gòu)造方法，可以只傳exchange的名字， 第二種，可以傳exchange名字，是否支持持久化，是否可以自動(dòng)刪除，//第三種在第二種參數(shù)上可以增加Map，Map中可以存放自定義exchange中的參數(shù)return new DirectExchange(Constants.IMMEDIATE_EXCHANGE, true, false); } @Bean public DirectExchange deadLetterExchange() {// 一共有三種構(gòu)造方法，可以只傳exchange的名字， 第二種，可以傳exchange名字，是否支持持久化，是否可以自動(dòng)刪除，//第三種在第二種參數(shù)上可以增加Map，Map中可以存放自定義exchange中的參數(shù)return new DirectExchange(Constants.DEAD_LETTER_EXCHANGE, true, false); } @Bean //把立即消費(fèi)的隊(duì)列和立即消費(fèi)的exchange綁定在一起 public Binding immediateBinding() {return BindingBuilder.bind(immediateQueue()).to(immediateExchange()).with(Constants.IMMEDIATE_ROUTING_KEY); } @Bean //把立即消費(fèi)的隊(duì)列和立即消費(fèi)的exchange綁定在一起 public Binding delayBinding() {return BindingBuilder.bind(delayQueue()).to(deadLetterExchange()).with(Constants.DELAY_ROUTING_KEY); }}

生產(chǎn)者生產(chǎn)消息

ImmediateSender.java

package com.example.demo.deadLetter;import java.text.SimpleDateFormat;import java.util.Date;import org.springframework.amqp.rabbit.core.RabbitTemplate;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.stereotype.Component;import com.example.demo.Constants.Constants;import com.example.demo.model.Booking;@Componentpublic class ImmediateSender { @Autowired private RabbitTemplate rabbitTemplate; public void send(Booking booking, int delayTime) {System.out.println('delayTime' + delayTime);SimpleDateFormat sdf = new SimpleDateFormat('yyyy-MM-dd HH:mm:ss');this.rabbitTemplate.convertAndSend(Constants.DEAD_LETTER_EXCHANGE, Constants.DELAY_ROUTING_KEY, booking, message -> { message.getMessageProperties().setExpiration(delayTime + ''); System.out.println(sdf.format(new Date()) + ' Delay sent.'); return message;}); }}

消費(fèi)者消費(fèi)消息

ImmediateReceiver.java

package com.example.demo.deadLetter;import org.springframework.amqp.rabbit.annotation.EnableRabbit;import org.springframework.amqp.rabbit.annotation.RabbitHandler;import org.springframework.amqp.rabbit.annotation.RabbitListener;import org.springframework.context.annotation.Configuration;import org.springframework.stereotype.Component;import com.example.demo.Constants.Constants;import com.example.demo.model.Booking;@Component@EnableRabbit@Configurationpublic class ImmediateReceiver { @RabbitListener(queues = Constants.IMMEDIATE_QUEUE) @RabbitHandler public void get(Booking booking) {System.out.println('收到延時(shí)消息了' + booking); }}

model類book

Book.java

package com.example.demo.model;import java.io.Serializable;import java.util.Date;public class Booking implements Serializable { private static final long serialVersionUID = 1L; private String bookingName; private Date bookingTime; private String bookingContent; private String operatorName; public Booking() { } public String getBookingName() {return bookingName; } public void setBookingName(String bookingName) {this.bookingName = bookingName; } public Date getBookingTime() {return bookingTime; } public void setBookingTime(Date bookingTime) {this.bookingTime = bookingTime; } public String getBookingContent() {return bookingContent; } public void setBookingContent(String bookingContent) {this.bookingContent = bookingContent; } public String getOperatorName() {return operatorName; } public void setOperatorName(String operatorName) {this.operatorName = operatorName; } @Override public String toString() {return super.toString(); }}

測(cè)試類

Test.java

package com.example.demo;import java.util.Date;import org.junit.Test;import org.junit.runner.RunWith;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.boot.test.context.SpringBootTest;import org.springframework.test.context.junit4.SpringRunner;import com.example.demo.Immediate.Sender;import com.example.demo.deadLetter.ImmediateSender;import com.example.demo.model.Booking;@RunWith(SpringRunner.class)@SpringBootTestpublic class RabbitMqTestApplicationTests { @Autowired ImmediateSender immediateSender; @Test public void test() { Booking booking = new Booking();booking.setBookingContent('hhaha');booking.setBookingName('預(yù)定房子');booking.setBookingTime(new Date());booking.setOperatorName('hellen'); immediateSender.send(booking, 1000); }}

總結(jié)第一種方式：經(jīng)過(guò)測(cè)試，我們可以發(fā)現(xiàn)，當(dāng)我們先增加一條過(guò)期時(shí)間大(10000)的A消息進(jìn)入，之后再增加一個(gè)過(guò)期時(shí)間小的(1000)消息B,并沒(méi)有出現(xiàn)想象中的B消息先被消費(fèi)，A消息后被消費(fèi)，而是出現(xiàn)了當(dāng)10000過(guò)去的時(shí)候，AB消息同時(shí)被消費(fèi)，也就是B消息的消費(fèi)被阻塞了。

為什么會(huì)出現(xiàn)這樣的現(xiàn)象呢？

我們知道利用TTL DLX特性實(shí)現(xiàn)的方式，實(shí)際上在第一個(gè)延時(shí)隊(duì)列C里面設(shè)置了dlx，生產(chǎn)者生產(chǎn)了一條帶ttl的消息放入了延時(shí)隊(duì)列C中，等到延時(shí)時(shí)間到了，延時(shí)隊(duì)列C中的消息變成了死信，根據(jù)延時(shí)隊(duì)列C中設(shè)置的dlx的exchange的轉(zhuǎn)發(fā)規(guī)則，轉(zhuǎn)發(fā)到了實(shí)際消費(fèi)隊(duì)列D中，當(dāng)該隊(duì)列中的監(jiān)聽器監(jiān)聽到消息時(shí)就會(huì)正式開始消費(fèi)。那么實(shí)際上延時(shí)隊(duì)列中的消息也是放入隊(duì)列中的，隊(duì)列滿足先進(jìn)先出，而延時(shí)大的消息A還沒(méi)出隊(duì)，所以B消息也不能順利出隊(duì)。

利用Rabbitmq的插件x-delay-message實(shí)現(xiàn)

為了解決上面的問(wèn)題，Rabbitmq實(shí)現(xiàn)了一個(gè)插件x-delay-message來(lái)實(shí)現(xiàn)延時(shí)隊(duì)列。

x-delay-message安裝

介紹Ubuntu系統(tǒng)下插件安裝方式：選擇rabbitmq_delayed_message_exchange插件，選擇3.6版本，進(jìn)行下載將安裝包進(jìn)行解壓

uzip rabbitmq_delayed_message_exchange-20171215-3.6.x.zip

將插件移到rabbitmq安裝的路徑

sudo cp -r rabbitmq_delayed_message_exchange-20171215-3.6.x.ez /usr/lib/rabbitmq/lib/rabbitmq_server-3.6.15/plugins

Enable插件

rabbitmq-plugins enable rabbitmq_delayed_message_exchange

windows同理

Springboot集成rabbitmq實(shí)現(xiàn)第二種方式

XdelayConfig.java

package com.example.demo.Xdelay;import java.util.HashMap;import java.util.Map;import org.springframework.amqp.core.Binding;import org.springframework.amqp.core.BindingBuilder;import org.springframework.amqp.core.CustomExchange;import org.springframework.amqp.core.Queue;import org.springframework.context.annotation.Bean;import org.springframework.context.annotation.Configuration;import com.example.demo.Constants.Constants;@Configurationpublic class XdelayConfig { // 創(chuàng)建一個(gè)立即消費(fèi)隊(duì)列 @Bean public Queue immediateQueue() {// 第一個(gè)參數(shù)是創(chuàng)建的queue的名字，第二個(gè)參數(shù)是是否支持持久化return new Queue(Constants.IMMEDIATE_QUEUE_XDELAY, true); } @Bean public CustomExchange delayExchange() {Map<String, Object> args = new HashMap<String, Object>();args.put('x-delayed-type', 'direct');return new CustomExchange(Constants.DELAYED_EXCHANGE_XDELAY, 'x-delayed-message', true, false, args); } @Bean public Binding bindingNotify() {return BindingBuilder.bind(immediateQueue()).to(delayExchange()).with(Constants.DELAY_ROUTING_KEY_XDELAY).noargs(); }}

XdelaySender.java

package com.example.demo.Xdelay;import java.text.SimpleDateFormat;import java.util.Date;import org.springframework.amqp.AmqpException;import org.springframework.amqp.core.Message;import org.springframework.amqp.core.MessagePostProcessor;import org.springframework.amqp.rabbit.core.RabbitTemplate;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.stereotype.Service;import com.example.demo.Constants.Constants;import com.example.demo.model.Booking;@Servicepublic class XdelaySender { @Autowired private RabbitTemplate rabbitTemplate; public void send(Booking booking, int delayTime) {System.out.println('delayTime' + delayTime);SimpleDateFormat sdf = new SimpleDateFormat('yyyy-MM-dd HH:mm:ss');this.rabbitTemplate.convertAndSend(Constants.DELAYED_EXCHANGE_XDELAY, Constants.DELAY_ROUTING_KEY_XDELAY, booking, new MessagePostProcessor() { @Override public Message postProcessMessage(Message message) throws AmqpException {message.getMessageProperties().setDelay(delayTime);System.out.println(sdf.format(new Date()) + ' Delay sent.');return message; }}); }}

XdelayReceiver.java

package com.example.demo.Xdelay;import org.springframework.amqp.rabbit.annotation.EnableRabbit;import org.springframework.amqp.rabbit.annotation.RabbitListener;import org.springframework.context.annotation.Configuration;import org.springframework.stereotype.Component;import com.example.demo.Constants.Constants;import com.example.demo.model.Booking;@Component@EnableRabbit@Configurationpublic class XdelayReceiver { @RabbitListener(queues = Constants.IMMEDIATE_QUEUE_XDELAY) public void get(Booking booking) {System.out.println('Receive' + booking); }}

Test.java

package com.example.demo;import java.util.Date;import org.junit.Test;import org.junit.runner.RunWith;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.boot.test.context.SpringBootTest;import org.springframework.test.context.junit4.SpringRunner;import com.example.demo.Xdelay.XdelaySender;import com.example.demo.model.Booking;@RunWith(SpringRunner.class)@SpringBootTestpublic class RabbitMqTestApplicationTests { @Autowired XdelaySender xdelaySender; @Test public void test11() { Booking booking = new Booking();booking.setBookingContent('hhaha');booking.setBookingName('預(yù)定房子');booking.setBookingTime(new Date());booking.setOperatorName('hellen');xdelaySender.send(booking, 2000); }}

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