来源: RabbitMQ保姆级教程最佳实践 – 佛祖让我来巡山 – 博客园
一、消息队列介绍
1、消息队列概念
1、MQ全称为Message Queue,消息队列(MQ)是⼀种应⽤程序对应⽤程序的通信⽅法。应⽤程序通过读写出⼊队列的消息(针对应⽤程序的数据)来通信,⽽⽆需专⽤连接来链接它们。2、消息传递指的是程序之间通过在消息中发送数据进⾏通信,⽽不是通过直接调⽤彼此来通信,直接调⽤通常是⽤于诸如远程过程调⽤的技术。
2、常⽤的消息队列产品
1、RabbitMQ 稳定可靠,数据⼀致,⽀持多协议,有消息确认,基于erlang语⾔2、Kafka ⾼吞吐,⾼性能,快速持久化,⽆消息确认,⽆消息遗漏,可能会有有重复消息,依赖于zookeeper,成本⾼.3、ActiveMQ 不够灵活轻巧,对队列较多情况⽀持不好.4、RocketMQ 性能好,⾼吞吐,⾼可⽤性,⽀持⼤规模分布式,协议⽀持单⼀
⼆、RabbitMQ
1、RabbitMQ介绍
1、RabbitMQ是⼀个在AMQP基础上完成的,可复⽤的企业消息系统。他遵循MozillaPublic License开源协议。2、AMQP,即Advanced Message Queuing Protocol, ⼀个提供统⼀消息服务的应⽤层标准⾼级消息队列协议,是应⽤层协议的⼀个开放标准,为⾯向消息的中间件设计。基于此协议的客户端与消息中间件可传递消息,并不受客户端/中间件不同产品,不同的开发语⾔等条件的限制。Erlang中的实现有 RabbitMQ等。3、主要特性:
- 保证可靠性 :使⽤⼀些机制来保证可靠性,如持久化、传输确认、发布确认
- 灵活的路由功能
- 可伸缩性:⽀持消息集群,多台RabbitMQ服务器可以组成⼀个集群
- ⾼可⽤性 :RabbitMQ集群中的某个节点出现问题时队列仍然可⽤
- ⽀持多种协议
- ⽀持多语⾔客户端
- 提供良好的管理界⾯
- 提供跟踪机制:如果消息出现异常,可以通过跟踪机制分析异常原因
- 提供插件机制:可通过插件进⾏多⽅⾯扩展
2、RabbitMQ安装和配置
3、RabbitMQ逻辑结构
三、RabbitMQ⽤户管理
RabbitMQ默认提供了⼀个guests账号,但是此账号不能⽤作远程登录,也就是不能在管理系统的登录;我们可以创建⼀个新的账号并授予响应的管理权限来实现远程登录
1、逻辑结构
⽤户虚拟主机队列
2、⽤户管理
2.1、命令⾏⽤户管理
1、在linux中使⽤命令⾏创建⽤户
## 进⼊到rabbit_mq的sbin⽬录 cd /usr/local/rabbitmq_server-3.7.0/sbin ## 新增⽤户 ./rabbitmqctl add_user ytao admin1232、设置⽤户级别
## ⽤户级别: ## 1.administrator 可以登录控制台、查看所有信息、可以对RabbitMQ进⾏管理 ## 2.monitoring 监控者 登录控制台、查看所有信息 ## 3.policymaker 策略制定者 登录控制台、指定策略 ## 4.managment 普通管理员 登录控制台 ./rabbitmqctl set_user_tags ytao administrator
2.2、管理系统进⾏⽤户管理
管理系统登录:访问http://localhost:15672/
四、RabbitMQ⼯作⽅式
RabbitMQ提供了多种消息的通信⽅式—⼯作模式 https://www.rabbitmq.com/getstarted.html消息通信是由两个⻆⾊完成:消息⽣产者(producer)和 消息消费者(Consumer)
1、简单模式
⼀个队列只有⼀个消费者
2、⼯作模式
多个消费者监听同⼀个队列
3、订阅模式
⼀个交换机绑定多个消息队列,每个消息队列有⼀个消费者监听
4、路由模式
⼀个交换机绑定多个消息队列,每个消息队列都由⾃⼰唯⼀的key,每个消息队列有⼀个消费者监听
五、RabbitMQ交换机和队列管理
1、创建队列
2、创建交换机
3、交换机绑定队列
六、在普通的Maven应⽤中使⽤MQ
1、简单模式
1.1、消息⽣产者
1、创建Maven项⽬
2、添加RabbitMQ连接所需要的依赖
<!-- https://mvnrepository.com/artifact/com.rabbitmq/amqp-client --> <dependency> <groupId>com.rabbitmq</groupId> <artifactId>amqp-client</artifactId> <version>4.10.0</version> </dependency> <!-- https://mvnrepository.com/artifact/org.slf4j/slf4j-log4j12 --> <dependency> <groupId>org.slf4j</groupId> <artifactId>slf4j-log4j12</artifactId> <version>1.7.25</version> <scope>test</scope> </dependency> <!-- https://mvnrepository.com/artifact/org.apache.commons/commonslang3 --> <dependency> <groupId>org.apache.commons</groupId> <artifactId>commons-lang3</artifactId> <version>3.9</version> </dependency>3、在resources⽬录下创建log4j.properties
log4j.rootLogger=DEBUG,A1 log4j.logger.com.taotao = DEBUG log4j.logger.org.mybatis = DEBUG log4j.appender.A1=org.apache.log4j.ConsoleAppender log4j.appender.A1.layout=org.apache.log4j.PatternLayout log4j.appender.A1.layout.ConversionPattern=%-d{yyyy-MM-dd HH:mm:ss,SSS} [%t] [%c]-[%p] %m%n4、创建MQ连接工具类
import com.rabbitmq.client.Connection; import com.rabbitmq.client.ConnectionFactory; import java.io.IOException; import java.util.concurrent.TimeoutException; public class ConnectionUtil { public static Connection getConnection() throws IOException, TimeoutException { //1.创建连接⼯⼚ ConnectionFactory factory = new ConnectionFactory(); //2.在⼯⼚对象中设置MQ的连接信息 (ip,port,virtualhost,username,password) factory.setHost("47.96.11.185"); factory.setPort(5672); factory.setVirtualHost("host1"); factory.setUsername("ytao"); factory.setPassword("admin123"); //3.通过⼯⼚对象获取与MQ的链接 Connection connection = factory.newConnection(); return connection; } }5、消息⽣产者发送消息
import com.qfedu.mq.utils.ConnectionUtil; import com.rabbitmq.client.Channel; import com.rabbitmq.client.Connection; public class SendMsg { public static void main(String[] args) throws Exception{ String msg = "Hello HuangDaoJun!"; Connection connection = ConnectionUtil.getConnection(); Channel channel = connection.createChannel(); //定义队列(使⽤Java代码在MQ中新建⼀个队列) //参数1:定义的队列名称 //参数2:队列中的数据是否持久化(如果选择了持久化) //参数3: 是否排外(当前队列是否为当前连接私有) //参数4:⾃动删除(当此队列的连接数为0时,此队列会销毁(⽆论队列中是否还有数据)) //参数5:设置当前队列的参数 //channel.queueDeclare("queue7",false,false,false,null); //参数1:交换机名称,如果直接发送信息到队列,则交换机名称为"" //参数2:⽬标队列名称 //参数3:设置当前这条消息的属性(设置过期时间 10) //参数4:消息的内容 channel.basicPublish("","queue1",null,msg.getBytes()); System.out.println("发送:" + msg); channel.close(); connection.close(); } }
1.2、消息消费者
1、创建Maven项⽬2、添加依赖3、log4j.properties4、ConnetionUtil.java5、消费者消费消息import com.qfedu.mq.utils.ConnectionUtil; import com.rabbitmq.client.*; import java.io.IOException; import java.util.concurrent.TimeoutException; public class ReceiveMsg { public static void main(String[] args) throws IOException, TimeoutException { Connection connection = ConnectionUtil.getConnection(); Channel channel = connection.createChannel(); Consumer consumer = new DefaultConsumer(channel){ @Override public void handleDelivery(String consumerTag, Envelope envelope, AMQP.BasicProperties properties, byte[] body) throws IOException { //body就是从队列中获取的数据 String msg = new String(body); System.out.println("接收:"+msg); } }; channel.basicConsume("queue1",true,consumer); } }
2、⼯作模式
⼀个发送者多个消费者
2.1、发送者
public class SendMsg { public static void main(String[] args) throws Exception{ System.out.println("请输⼊消息:"); Scanner scanner = new Scanner(System.in); String msg = null; while(!"quit".equals(msg = scanner.nextLine())){ Connection connection = ConnectionUtil.getConnection(); Channel channel = connection.createChannel(); channel.basicPublish("","queue2",null,msg.getBytes()); System.out.println("发送:" + msg); channel.close(); connection.close(); } } }
2.2、消费者1
public class ReceiveMsg { public static void main(String[] args) throws Exception { Connection connection = ConnectionUtil.getConnection(); Channel channel = connection.createChannel(); Consumer consumer = new DefaultConsumer(channel){ @Override public void handleDelivery(String consumerTag, Envelope envelope, AMQP.BasicProperties properties, byte[] body) throws IOException { //body就是从队列中获取的数据 String msg = new String(body); System.out.println("Consumer1接收:"+msg); if("wait".equals(msg)){ try { Thread.sleep(10000); } catch (InterruptedException e) { e.printStackTrace(); } } } }; channel.basicConsume("queue2",true,consumer); } }
2.3、消费者2
public class ReceiveMsg { public static void main(String[] args) throws IOException, TimeoutException { Connection connection = ConnectionUtil.getConnection(); Channel channel = connection.createChannel(); Consumer consumer = new DefaultConsumer(channel){ @Override public void handleDelivery(String consumerTag, Envelope envelope, AMQP.BasicProperties properties, byte[] body) throws IOException { //body就是从队列中获取的数据 String msg = new String(body); System.out.println("Consumer2接收:"+msg); } }; channel.basicConsume("queue2",true,consumer); } }
3、订阅模式
1、发送者 发送消息到交换机
public class SendMsg { public static void main(String[] args) throws Exception{ System.out.println("请输⼊消息:"); Scanner scanner = new Scanner(System.in); String msg = null; while(!"quit".equals(msg = scanner.nextLine())){ Connection connection = ConnectionUtil.getConnection(); Channel channel = connection.createChannel(); channel.basicPublish("ex1","",null,msg.getBytes()); System.out.println("发送:" + msg); channel.close(); connection.close(); } } }
2、消费者1
public class ReceiveMsg1 { public static void main(String[] args) throws Exception { Connection connection = ConnectionUtil.getConnection(); Channel channel = connection.createChannel(); Consumer consumer = new DefaultConsumer(channel){ @Override public void handleDelivery(String consumerTag, Envelope envelope, AMQP.BasicProperties properties, byte[] body) throws IOException { //body就是从队列中获取的数据 String msg = new String(body); System.out.println("Consumer1接收:"+msg); if("wait".equals(msg)){ try { Thread.sleep(10000); } catch (InterruptedException e) { e.printStackTrace(); } } } }; channel.basicConsume("queue3",true,consumer); } }
3、消费者2
public class ReceiveMsg2 { public static void main(String[] args) throws IOException, TimeoutException { Connection connection = ConnectionUtil.getConnection(); Channel channel = connection.createChannel(); Consumer consumer = new DefaultConsumer(channel){ @Override public void handleDelivery(String consumerTag, Envelope envelope, AMQP.BasicProperties properties, byte[] body) throws IOException { //body就是从队列中获取的数据 String msg = new String(body); System.out.println("Consumer2接收:"+msg); } } ; channel.basicConsume("queue4",true,consumer); } }
4、路由模式
1、发送者 发送消息到交换机
public class SendMsg { public static void main(String[] args) throws Exception{ System.out.println("请输⼊消息:"); Scanner scanner = new Scanner(System.in); String msg = null; while(!"quit".equals(msg = scanner.nextLine())){ Connection connection = ConnectionUtil.getConnection(); Channel channel = connection.createChannel(); if(msg.startsWith("a")){ channel.basicPublish("ex2","a",null,msg.getBytes()); } else if(msg.startsWith("b")){ channel.basicPublish("ex2","b",null,msg.getBytes()); } System.out.println("发送:" + msg); channel.close(); connection.close(); } } }
2、消费者1
public class ReceiveMsg1 { public static void main(String[] args) throws Exception { Connection connection = ConnectionUtil.getConnection(); Channel channel = connection.createChannel(); Consumer consumer = new DefaultConsumer(channel){ @Override public void handleDelivery(String consumerTag, Envelope envelope, AMQP.BasicProperties properties, byte[] body) throws IOException { //body就是从队列中获取的数据 String msg = new String(body); System.out.println("Consumer1接收:"+msg); if("wait".equals(msg)){ try { Thread.sleep(10000); } catch (InterruptedException e) { e.printStackTrace(); } } } }; channel.basicConsume("queue5",true,consumer); } }
3、消费者2
public class ReceiveMsg2 { public static void main(String[] args) throws IOException, TimeoutException { Connection connection = ConnectionUtil.getConnection(); Channel channel = connection.createChannel(); Consumer consumer = new DefaultConsumer(channel){ @Override public void handleDelivery(String consumerTag, Envelope envelope, AMQP.BasicProperties properties, byte[] body) throws IOException { //body就是从队列中获取的数据 String msg = new String(body); System.out.println("Consumer2接收:"+msg); } }; channel.basicConsume("queue6",true,consumer); } }
七、在SpringBoot应⽤中使⽤MQ
SpringBoot应⽤可以完成⾃动配置及依赖注⼊——可以通过Spring直接提供与MQ的连接对象
1、消息⽣产者
1、创建SpringBoot应⽤,添加依赖
2、配置application.yml
server: port: 9001 spring: application: name: producer rabbitmq: host: 47.96.11.185 port: 5672 virtual-host: host1 username: ytao password: admin1233、发送消息
@Service public class TestService { @Resource private AmqpTemplate amqpTemplate; public void sendMsg(String msg){ //1. 发送消息到队列 amqpTemplate.convertAndSend("queue1",msg); //2. 发送消息到交换机(订阅交换机) amqpTemplate.convertAndSend("ex1","",msg); //3. 发送消息到交换机(路由交换机) amqpTemplate.convertAndSend("ex2","a",msg); } }
2、消息消费者
1、创建项⽬添加依赖2、配置yml3、接收消息@Service //@RabbitListener(queues = {"queue1","queue2"}) @RabbitListener(queues = "queue1") public class ReceiveMsgService { @RabbitHandler public void receiveMsg(String msg){ System.out.println("接收MSG:"+msg); } }
⼋、使⽤RabbitMQ传递对象
RabbitMQ是消息队列,发送和接收的都是字符串/字节数组类型的消息
1、使⽤序列化对象
要求:传递的对象实现序列化接⼝传递的对象的包名、类名、属性名必须⼀致
1、消息提供者
@Service public class MQService { @Resource private AmqpTemplate amqpTemplate; public void sendGoodsToMq(Goods goods){ //消息队列可以发送 字符串、字节数组、序列化对象 amqpTemplate.convertAndSend("","queue1",goods); } }2、消息消费者
@Component @RabbitListener(queues = "queue1") public class ReceiveService { @RabbitHandler public void receiveMsg(Goods goods){ System.out.println("Goods---"+goods); } }
2、使⽤序列化字节数组
要求:传递的对象实现序列化接⼝传递的对象的包名、类名、属性名必须⼀致
1、消息提供者
@Service public class MQService { @Resource private AmqpTemplate amqpTemplate; public void sendGoodsToMq(Goods goods){ //消息队列可以发送 字符串、字节数组、序列化对象 byte[] bytes = SerializationUtils.serialize(goods); amqpTemplate.convertAndSend("","queue1",bytes); } }2、消息消费者
@Component @RabbitListener(queues = "queue1") public class ReceiveService { @RabbitHandler public void receiveMsg(byte[] bs){ Goods goods = (Goods) SerializationUtils.deserialize(bs); System.out.println("byte[]---"+goods); } }
3、使⽤JSON字符串传递
要求:对象的属性名⼀直
1、消息提供者
@Service public class MQService { @Resource private AmqpTemplate amqpTemplate; public void sendGoodsToMq(Goods goods) throws JsonProcessingException { //消息队列可以发送 字符串、字节数组、序列化对象 ObjectMapper objectMapper = new ObjectMapper(); String msg = objectMapper.writeValueAsString(goods); amqpTemplate.convertAndSend("","queue1",msg); } }2、消息消费者
@Component @RabbitListener(queues = "queue1") public class ReceiveService { @RabbitHandler public void receiveMsg(String msg) throws JsonProcessingException { ObjectMapper objectMapper = new ObjectMapper(); Goods goods = objectMapper.readValue(msg,Goods.class); System.out.println("String---"+msg); } }
九、基于Java的交换机与队列创建
我们使⽤消息队列,消息队列和交换机可以通过管理系统完成创建,也可以在应⽤程序中通过Java代码来完成创建
1、普通Maven项⽬交换机及队列创建
1、使⽤Java代码新建队列
//1.定义队列 (使⽤Java代码在MQ中新建⼀个队列) //参数1:定义的队列名称 //参数2:队列中的数据是否持久化(如果选择了持久化) //参数3: 是否排外(当前队列是否为当前连接私有) //参数4:⾃动删除(当此队列的连接数为0时,此队列会销毁(⽆论队列中是否还有数据)) //参数5:设置当前队列的参数 channel.queueDeclare("queue7",false,false,false,null);2、新建交换机
//定义⼀个“订阅交换机” channel.exchangeDeclare("ex3", BuiltinExchangeType.FANOUT); //定义⼀个“路由交换机” channel.exchangeDeclare("ex4", BuiltinExchangeType.DIRECT);3、绑定队列到交换机
//绑定队列 //参数1:队列名称 //参数2:⽬标交换机 //参数3:如果绑定订阅交换机参数为"",如果绑定路由交换机则表示设置队列的key channel.queueBind("queue7","ex4","k1"); channel.queueBind("queue8","ex4","k2");
2、SpringBoot应⽤中通过配置完成队列的创建
@Configuration public class RabbitMQConfiguration { //声明队列 @Bean public Queue queue9(){ Queue queue9 = new Queue("queue9"); //设置队列属性 return queue9; } @Bean public Queue queue10(){ Queue queue10 = new Queue("queue10"); //设置队列属性 return queue10; } //声明订阅模式交换机 @Bean public FanoutExchange ex5(){ return new FanoutExchange("ex5"); } //声明路由模式交换机 @Bean public DirectExchange ex6(){ return new DirectExchange("ex6"); } //绑定队列 @Bean public Binding bindingQueue9(Queue queue9, DirectExchange ex6){ return BindingBuilder.bind(queue9).to(ex6).with("k1"); } @Bean public Binding bindingQueue10(Queue queue10, DirectExchange ex6){ return BindingBuilder.bind(queue10).to(ex6).with("k2"); } }
⼗、消息的可靠性
消息的可靠性:从 ⽣产者发送消息 —— 消息队列存储消息 —— 消费者消费消息 的整个过程中消息的安全性及可控性。
- ⽣产者
- 消息队列
- 消费者
1、RabbitMQ事务
RabbitMQ事务指的是基于客户端实现的事务管理,当在消息发送过程中添加了事务,处理效率降低⼏⼗倍甚⾄上百倍
Connection connection = RabbitMQUtil.getConnection(); //connection 表示与 host1的连接 Channel channel = connection.createChannel(); channel.txSelect();//开启事务 try{ channel.basicPublish("ex4", "k1", null, msg.getBytes()); channel.txCommit();//提交事务 } catch (Exception e){ channel.txRollback();//事务回滚 } finally{ channel.close(); connection.close(); }
2、RabbitMQ消息确认和return机制
1、消息确认机制:确认消息提供者是否成功发送消息到交换机2、return机制:确认消息是否成功的从交换机分发到队列
2.1、普通Maven项⽬的消息确认
1、普通confirm⽅式
//1.发送消息之前开启消息确认 channel.confirmSelect(); channel.basicPublish("ex1", "a", null, msg.getBytes()); //2.接收消息确认 Boolean b = channel.waitForConfirms(); System.out.println("发送:" +(b?"成功":"失败"));2、批量confirm⽅式
//1.发送消息之前开启消息确认 channel.confirmSelect(); //2.批量发送消息 for (int i=0 ; i<10 ; i++){ channel.basicPublish("ex1", "a", null, msg.getBytes()); } //3.接收批量消息确认:发送的所有消息中,如果有⼀条是失败的,则所有消息发送直接失败,抛出IO异常 Boolean b = channel.waitForConfirms();3、异步confirm⽅式
//发送消息之前开启消息确认 channel.confirmSelect(); //批量发送消息 for (int i=0 ; i<10 ; i++){ channel.basicPublish("ex1", "a", null, msg.getBytes()); } //假如发送消息需要10s,waitForConfirms会进⼊阻塞状态 //boolean b = channel.waitForConfirms(); //使⽤监听器异步confirm channel.addConfirmListener(new ConfirmListener() { //参数1: long l 返回消息的表示 //参数2: boolean b 是否为批量confirm public void handleAck(long l, Boolean b) throws IOException { System.out.println("~~~~~消息成功发送到交换机"); } public void handleNack(long l, Boolean b) throws IOException { System.out.println("~~~~~消息发送到交换机失败"); } } );
2.2、普通Maven项⽬的return机制
1、添加return监听器2、发送消息是指定第三个参数为true3、由于监听器监听是异步处理,所以在消息发送之后不能关闭channelString msg = "Hello HuangDaoJun!"; Connection connection = ConnectionUtil.getConnection(); //相当于JDBC操作的数据库连接 Channel channel = connection.createChannel(); //相当于JDBC操作的statement //return机制:监控交换机是否将消息分发到队列 channel.addReturnListener(new ReturnListener() { public void handleReturn(int i, String s, String s1, String s2,AMQP.BasicProperties basicProperties,byte[] bytes) throws IOException { //如果交换机分发消息到队列失败,则会执⾏此⽅法(⽤来处理交换机分发消息到队列失败的情况) System.out.println("*****"+i);//标识 System.out.println("*****"+s);// System.out.println("*****"+s1);//交换机名 System.out.println("*****"+s2);//交换机对应的队列的key System.out.println("*****"+new String(bytes));//发送的消息 } } ); //发送消息 //channel.basicPublish("ex2", "c", null, msg.getBytes()); channel.basicPublish("ex2", "c", true, null, msg.getBytes());
2.3、在SpringBoot应⽤实现消息确认与return监听
1、配置application.yml,开启消息确认和return监听
spring: rabbitmq: publisher-confirm-type: simple ## 开启消息确认模式 publisher-returns: true ##使⽤return监听机制2、创建confirm和return监听
2.1、消息确认
@Component public class MyConfirmListener implements RabbitTemplate.ConfirmCallback { @Autowired private AmqpTemplate amqpTemplate; @Autowired private RabbitTemplate rabbitTemplate; @PostConstruct public void init(){ rabbitTemplate.setConfirmCallback(this); } @Override public void confirm(CorrelationData correlationData, Boolean b, String s) { //参数b 表示消息确认结果 //参数s 表示发送的消息 if(b){ System.out.println("消息发送到交换机成功!"); } else{ System.out.println("消息发送到交换机失败!"); amqpTemplate.convertAndSend("ex4","",s); } } }2.2、return机制
@Component public class MyReturnListener implements RabbitTemplate.ReturnsCallback { @Autowired private AmqpTemplate amqpTemplate; @Autowired private RabbitTemplate rabbitTemplate; @PostConstruct public void init(){ rabbitTemplate.setReturnsCallback(this); } @Override public void returnedMessage(ReturnedMessage returnedMessage) { System.out.println("消息从交换机分发到队列失败"); String exchange = returnedMessage.getExchange(); String routingKey = returnedMessage.getRoutingKey(); String msg = returnedMessage.getMessage().toString(); amqpTemplate.convertAndSend(exchange,routingKey,msg); } }
3、RabbitMQ消费者⼿动应答
@Component @RabbitListener(queues="queue01") public class Consumer1 { @RabbitHandler public void process(String msg,Channel channel, Message message) throws IOException { try { System.out.println("get msg1 success msg = "+msg); /** * 确认⼀条消息:<br> * channel.basicAck(deliveryTag, false); <br> * deliveryTag:该消息的index <br> * multiple:是否批量.true:将⼀次性ack所有⼩于deliveryTag的消息 <br> */ channel.basicAck(message.getMessageProperties().getDeliveryTag(), false); } catch (Exception e) { //消费者处理出了问题,需要告诉队列信息消费失败 /** * 拒绝确认消息:<br> * channel.basicNack(long deliveryTag, boolean multiple, boolean requeue) ; <br> * deliveryTag:该消息的index<br> * multiple:是否批量.true:将⼀次性拒绝所有⼩于deliveryTag的消息。<br> * requeue:被拒绝的是否重新⼊队列 <br> */ channel.basicNack(message.getMessageProperties().getDeliveryTag(), false, true); System.err.println("get msg1 failed msg = "+msg); } } }
4、消息消费的幂等性问题
消息消费的幂等性——多次消费的执⾏结果时相同的 (避免重复消费)解决⽅案:处理成功的消息setnx到redis
⼗⼀、延迟机制
1、延迟队列
1、延迟队列——消息进⼊到队列之后,延迟指定的时间才能被消费者消费2、AMQP协议和RabbitMQ队列本身是不⽀持延迟队列功能的,但是可以通过TTL(Time To Live)特性模拟延迟队列的功能3、TTL就是消息的存活时间。RabbitMQ可以分别对队列和消息设置存活时间
1、在创建队列的时候可以设置队列的存活时间,当消息进⼊到队列并且在存活时间内没有消费者消费,则此消息就会从当前队列被移除;2、创建消息队列没有设置TTL,但是消息设置了TTL,那么当消息的存活时间结束,也会被移除;3、当TTL结束之后,我们可以指定将当前队列的消息转存到其他指定的队列
2、使⽤延迟队列实现订单⽀付监控
1、实现流程图
2、创建交换机和队列
⼗⼆、消息队列作⽤/使⽤场景总结
1、解耦
场景说明:⽤户下单之后,订单系统要通知库存系统
2、异步
场景说明:⽤户注册成功之后,需要发送注册邮件及注册短信提醒
3、消息通信
场景说明:应⽤系统之间的通信,例如聊天室
4、流量削峰
场景说明:秒杀业务
5、⽇志处理
场景说明:系统中⼤量的⽇志处理