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死信队列

死信的概念

先从概念解释上搞清楚这个定义，死信，顾名思义就是无法被消费的消息，字面意思可以这样理解，一般来说，producer 将消息投递到 broker 或者直接到queue 里了，consumer 从 queue 取出消息进行消费，但某些时候由于特定的原因导致queue 中的某些消息无法被消费，这样的消息如果没有后续的处理，就变成了死信，有死信自然就有了死信队列.

应用场景:为了保证订单业务的消息数据不丢失，需要使用到 RabbitMQ 的死信队列机制，当消息消费发生异常时，将消息投入死信队列中.还有比如说: 用户在商城下单成功并点击去支付后在指定时间未支付时自动失效

造成死信的原因

• 消息 TTL 过期
• 队列达到最大长度(队列满了，无法再添加数据到 MQ 中)
• 消息被拒绝(basic.reject 或 basic.nack)并且 requeue=false.

死信架构图

代码实战

• TTL过期

  package com.vmware.rabbit.demo8;import com.rabbitmq.client.BuiltinExchangeType;
  import com.rabbitmq.client.Channel;
  import com.rabbitmq.client.Connection;
  import com.rabbitmq.client.DeliverCallback;
  import com.vmware.rabbit.utils.RabbitUtil;import java.util.HashMap;public class Consumer {//普通交换机private static final String NORMAL_EXCHANGE = "normal_exchange";//死信交换机private static final String DEAD_EXCHANGE = "dead_exchange";//普通队列private static final String NORMAL_QUEUE = "normal_queue";//死信队列private static final String DEAD_QUEUE = "dead_queue";public static void main(String[] args) throws Exception {Connection connection = RabbitUtil.getConnection();Channel channel = connection.createChannel();//创建普通队列死信分发参数HashMap<String,Object> arguments= new HashMap<>();arguments.put("x-dead-letter-exchange",DEAD_EXCHANGE);arguments.put("x-dead-letter-routing-key","lisi");//创建普通交换机与队列并绑定channel.exchangeDeclare(NORMAL_EXCHANGE, BuiltinExchangeType.DIRECT);channel.queueDeclare(NORMAL_QUEUE,false,false,false,arguments);channel.queueBind(NORMAL_QUEUE,NORMAL_EXCHANGE,"zhangsan");//创建死信交换机和队列并绑定channel.exchangeDeclare(DEAD_EXCHANGE,BuiltinExchangeType.DIRECT);channel.queueDeclare(DEAD_QUEUE,false,false,false,null);channel.queueBind(DEAD_QUEUE,DEAD_EXCHANGE,"lisi");DeliverCallback deliverCallback= (tag,msg)->{String message = new String(msg.getBody());System.out.println("接收到消息:"+message);}};//创建消费者channel.basicConsume(NORMAL_QUEUE,false,deliverCallback,(tag)->{});}
  }
  

  package com.vmware.rabbit.demo8;import com.rabbitmq.client.AMQP;
  import com.rabbitmq.client.Channel;
  import com.rabbitmq.client.Connection;
  import com.vmware.rabbit.utils.RabbitUtil;public class Producer {private static final String EXCHANGE_NAME = "normal_exchange";private static final String ROUTING_KEY = "zhangsan";public static void main(String[] args) throws Exception {Connection connection = RabbitUtil.getConnection();System.out.println("已连接到RabbitMQ服务器....");Channel channel = connection.createChannel();//设置超时为10秒AMQP.BasicProperties basicProperties = new AMQP.BasicProperties().builder().expiration("10000").build();for (int i = 0; i < 10; i++) {String message = "msg" + i;channel.basicPublish(EXCHANGE_NAME, ROUTING_KEY, basicProperties, message.getBytes());System.out.println("消息:"+message+"发送成功!");}}
  }
  

• 队列达到最大长度

  package com.vmware.rabbit.demo8;import com.rabbitmq.client.BuiltinExchangeType;
  import com.rabbitmq.client.Channel;
  import com.rabbitmq.client.Connection;
  import com.rabbitmq.client.DeliverCallback;
  import com.vmware.rabbit.utils.RabbitUtil;import java.util.HashMap;public class Consumer {//普通交换机private static final String NORMAL_EXCHANGE = "normal_exchange";//死信交换机private static final String DEAD_EXCHANGE = "dead_exchange";//普通队列private static final String NORMAL_QUEUE = "normal_queue";//死信队列private static final String DEAD_QUEUE = "dead_queue";public static void main(String[] args) throws Exception {Connection connection = RabbitUtil.getConnection();Channel channel = connection.createChannel();//创建普通队列死信分发参数HashMap<String,Object> arguments= new HashMap<>();arguments.put("x-dead-letter-exchange",DEAD_EXCHANGE);arguments.put("x-dead-letter-routing-key","lisi");//设置队列最大长度arguments.put("x-max-length",5);//创建普通交换机与队列并绑定channel.exchangeDeclare(NORMAL_EXCHANGE, BuiltinExchangeType.DIRECT);channel.queueDeclare(NORMAL_QUEUE,false,false,false,arguments);channel.queueBind(NORMAL_QUEUE,NORMAL_EXCHANGE,"zhangsan");//创建死信交换机和队列并绑定channel.exchangeDeclare(DEAD_EXCHANGE,BuiltinExchangeType.DIRECT);channel.queueDeclare(DEAD_QUEUE,false,false,false,null);channel.queueBind(DEAD_QUEUE,DEAD_EXCHANGE,"lisi");DeliverCallback deliverCallback= (tag,msg)->{String message = new String(msg.getBody());System.out.println("消息:"+message+"被拒绝");};//创建消费者channel.basicConsume(NORMAL_QUEUE,false,deliverCallback,(tag)->{});}
  }
  

  package com.vmware.rabbit.demo8;import com.rabbitmq.client.AMQP;
  import com.rabbitmq.client.Channel;
  import com.rabbitmq.client.Connection;
  import com.vmware.rabbit.utils.RabbitUtil;public class Producer {private static final String EXCHANGE_NAME = "normal_exchange";private static final String ROUTING_KEY = "zhangsan";public static void main(String[] args) throws Exception {Connection connection = RabbitUtil.getConnection();System.out.println("已连接到RabbitMQ服务器....");Channel channel = connection.createChannel();for (int i = 0; i < 10; i++) {String message = "msg" + i;channel.basicPublish(EXCHANGE_NAME, ROUTING_KEY, null, message.getBytes());System.out.println("消息:"+message+"发送成功!");}}
  }
  

• 消息被拒

  package com.vmware.rabbit.demo8;import com.rabbitmq.client.BuiltinExchangeType;
  import com.rabbitmq.client.Channel;
  import com.rabbitmq.client.Connection;
  import com.rabbitmq.client.DeliverCallback;
  import com.vmware.rabbit.utils.RabbitUtil;import java.util.HashMap;public class Consumer {//普通交换机private static final String NORMAL_EXCHANGE = "normal_exchange";//死信交换机private static final String DEAD_EXCHANGE = "dead_exchange";//普通队列private static final String NORMAL_QUEUE = "normal_queue";//死信队列private static final String DEAD_QUEUE = "dead_queue";public static void main(String[] args) throws Exception {Connection connection = RabbitUtil.getConnection();Channel channel = connection.createChannel();//创建普通队列死信分发参数HashMap<String,Object> arguments= new HashMap<>();arguments.put("x-dead-letter-exchange",DEAD_EXCHANGE);arguments.put("x-dead-letter-routing-key","lisi");//创建普通交换机与队列并绑定channel.exchangeDeclare(NORMAL_EXCHANGE, BuiltinExchangeType.DIRECT);channel.queueDeclare(NORMAL_QUEUE,false,false,false,arguments);channel.queueBind(NORMAL_QUEUE,NORMAL_EXCHANGE,"zhangsan");//创建死信交换机和队列并绑定channel.exchangeDeclare(DEAD_EXCHANGE,BuiltinExchangeType.DIRECT);channel.queueDeclare(DEAD_QUEUE,false,false,false,null);channel.queueBind(DEAD_QUEUE,DEAD_EXCHANGE,"lisi");DeliverCallback deliverCallback= (tag,msg)->{String message = new String(msg.getBody());if (message.equals("msg5")){System.out.println("消息:"+message+"被拒绝");channel.basicReject(msg.getEnvelope().getDeliveryTag(),false);}else {System.out.println("接收到消息:"+message);channel.basicAck(msg.getEnvelope().getDeliveryTag(),false);}};//创建消费者channel.basicConsume(NORMAL_QUEUE,false,deliverCallback,(tag)->{});}
  }
  

  package com.vmware.rabbit.demo8;import com.rabbitmq.client.Channel;
  import com.rabbitmq.client.Connection;
  import com.rabbitmq.client.DeliverCallback;
  import com.vmware.rabbit.utils.RabbitUtil;public class Consumer2 {private static final String DEAD_QUEUE_NAME = "dead_queue";public static void main(String[] args)throws Exception {Connection connection = RabbitUtil.getConnection();Channel channel = connection.createChannel();DeliverCallback deliverCallback=(tag,msg)->{String message= new String(msg.getBody());System.out.println("队列:"+DEAD_QUEUE_NAME+"\t收到消息:"+message);};channel.basicConsume(DEAD_QUEUE_NAME,true,deliverCallback,(tag)->{});}
  }
  

  package com.vmware.rabbit.demo8;import com.rabbitmq.client.AMQP;
  import com.rabbitmq.client.Channel;
  import com.rabbitmq.client.Connection;
  import com.vmware.rabbit.utils.RabbitUtil;public class Producer {private static final String EXCHANGE_NAME = "normal_exchange";private static final String ROUTING_KEY = "zhangsan";public static void main(String[] args) throws Exception {Connection connection = RabbitUtil.getConnection();System.out.println("已连接到RabbitMQ服务器....");Channel channel = connection.createChannel();for (int i = 0; i < 10; i++) {String message = "msg" + i;channel.basicPublish(EXCHANGE_NAME, ROUTING_KEY, null, message.getBytes());System.out.println("消息:"+message+"发送成功!");}}
  }