RabbitMQ之死信队列-阿里云开发者社区

文章目录

一、死信的概念

一、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。

二、死信的来源

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.

三、实战

1、消息 TTL 过期

生产者代码：

publicclassProducer {
privatestaticfinalStringNORMAL_EXCHANGE="normal_exchange";
publicstaticvoidmain(String[] argv) throwsException {
try (Channelchannel=RabbitMqUtils.getChannel()) {
channel.exchangeDeclare(NORMAL_EXCHANGE, BuiltinExchangeType.DIRECT);
//设置消息的 TTL 时间AMQP.BasicPropertiesproperties=newAMQP.BasicProperties().builder().expiration("10000").build();
//该信息是用作演示队列个数限制for (inti=1; i<11 ; i++) {
Stringmessage="info"+i;
channel.basicPublish(NORMAL_EXCHANGE, "zhangsan", properties, message.getBytes());
System.out.println("生产者发送消息:"+message);
            }
        }
    }
}

消费者 C1 代码(启动之后关闭该消费者模拟其接收不到消息)

publicclassConsumer01 {
//普通交换机名称privatestaticfinalStringNORMAL_EXCHANGE="normal_exchange";
//死信交换机名称privatestaticfinalStringDEAD_EXCHANGE="dead_exchange";
publicstaticvoidmain(String[] argv) throwsException {
Channelchannel=RabbitUtils.getChannel();
//声明死信和普通交换机 类型为 directchannel.exchangeDeclare(NORMAL_EXCHANGE, BuiltinExchangeType.DIRECT);
channel.exchangeDeclare(DEAD_EXCHANGE, BuiltinExchangeType.DIRECT);
//声明死信队列StringdeadQueue="dead-queue";
channel.queueDeclare(deadQueue, false, false, false, null);
//死信队列绑定死信交换机与 routingkeychannel.queueBind(deadQueue, DEAD_EXCHANGE, "lisi");
//正常队列绑定死信队列信息Map<String, Object>params=newHashMap<>();
//正常队列设置死信交换机 参数 key 是固定值params.put("x-dead-letter-exchange", DEAD_EXCHANGE);
//正常队列设置死信 routing-key 参数 key 是固定值params.put("x-dead-letter-routing-key", "lisi");
StringnormalQueue="normal-queue";
channel.queueDeclare(normalQueue, false, false, false, params);
channel.queueBind(normalQueue, NORMAL_EXCHANGE, "zhangsan");
System.out.println("等待接收消息.....");
DeliverCallbackdeliverCallback= (consumerTag, delivery) -> {
Stringmessage=newString(delivery.getBody(), "UTF-8");
System.out.println("Consumer01 接收到消息"+message);
        };
channel.basicConsume(normalQueue, true, deliverCallback, consumerTag-> {
        });
    }
}

消费者 C2 代码(以上步骤完成后启动 C2 消费者它消费死信队列里面的消息)

publicclassConsumer02 {
privatestaticfinalStringDEAD_EXCHANGE="dead_exchange";
publicstaticvoidmain(String[] argv) throwsException {
Channelchannel=RabbitUtils.getChannel();
channel.exchangeDeclare(DEAD_EXCHANGE, BuiltinExchangeType.DIRECT);
StringdeadQueue="dead-queue";
channel.queueDeclare(deadQueue, false, false, false, null);
channel.queueBind(deadQueue, DEAD_EXCHANGE, "lisi");
System.out.println("等待接收死信队列消息.....");
DeliverCallbackdeliverCallback= (consumerTag, delivery) -> {
Stringmessage=newString(delivery.getBody(), "UTF-8");
System.out.println("Consumer02 接收死信队列的消息"+message);
        };
channel.basicConsume(deadQueue, true, deliverCallback, consumerTag-> {
        });
    }
}

2、队列达到最大长度

消息生产者代码去掉 TTL 属性

publicclassProducer {
privatestaticfinalStringNORMAL_EXCHANGE="normal_exchange";
publicstaticvoidmain(String[] argv) throwsException {
try (Channelchannel=RabbitMqUtils.getChannel()) {
channel.exchangeDeclare(NORMAL_EXCHANGE, BuiltinExchangeType.DIRECT);
//该信息是用作演示队列个数限制for (inti=1; i<11 ; i++) {
Stringmessage="info"+i;
channel.basicPublish(NORMAL_EXCHANGE,"zhangsan",null, message.getBytes());
System.out.println("生产者发送消息:"+message);
            }
        }
    }
}

C1 消费者修改以下代码(启动之后关闭该消费者模拟其接收不到消息)

publicclassConsumer01 {
//普通交换机名称privatestaticfinalStringNORMAL_EXCHANGE="normal_exchange";
//死信交换机名称privatestaticfinalStringDEAD_EXCHANGE="dead_exchange";
publicstaticvoidmain(String[] argv) throwsException {
Channelchannel=RabbitUtils.getChannel();
//声明死信和普通交换机 类型为 directchannel.exchangeDeclare(NORMAL_EXCHANGE, BuiltinExchangeType.DIRECT);
channel.exchangeDeclare(DEAD_EXCHANGE, BuiltinExchangeType.DIRECT);
//声明死信队列StringdeadQueue="dead-queue";
channel.queueDeclare(deadQueue, false, false, false, null);
//死信队列绑定死信交换机与 routingkeychannel.queueBind(deadQueue, DEAD_EXCHANGE, "lisi");
//正常队列绑定死信队列信息Map<String, Object>params=newHashMap<>();
//正常队列设置死信交换机 参数 key 是固定值params.put("x-dead-letter-exchange", DEAD_EXCHANGE);
//正常队列设置死信 routing-key 参数 key 是固定值params.put("x-dead-letter-routing-key", "lisi");
//设置正常队列长度限制params.put("x-max-length",6);
StringnormalQueue="normal-queue";
channel.queueDeclare(normalQueue, false, false, false, params);
channel.queueBind(normalQueue, NORMAL_EXCHANGE, "zhangsan");
System.out.println("等待接收消息.....");
DeliverCallbackdeliverCallback= (consumerTag, delivery) -> {
Stringmessage=newString(delivery.getBody(), "UTF-8");
System.out.println("Consumer01 接收到消息"+message);
        };
channel.basicConsume(normalQueue, true, deliverCallback, consumerTag-> {
        });
    }
}

注意此时需要把原先队列删除因为参数改变了

C2 消费者代码

publicclassConsumer02 {
privatestaticfinalStringDEAD_EXCHANGE="dead_exchange";
publicstaticvoidmain(String[] argv) throwsException {
Channelchannel=RabbitUtils.getChannel();
channel.exchangeDeclare(DEAD_EXCHANGE, BuiltinExchangeType.DIRECT);
StringdeadQueue="dead-queue";
channel.queueDeclare(deadQueue, false, false, false, null);
channel.queueBind(deadQueue, DEAD_EXCHANGE, "lisi");
System.out.println("等待接收死信队列消息.....");
DeliverCallbackdeliverCallback= (consumerTag, delivery) -> {
Stringmessage=newString(delivery.getBody(), "UTF-8");
System.out.println("Consumer02 接收死信队列的消息"+message);
        };
channel.basicConsume(deadQueue, true, deliverCallback, consumerTag-> {
        });
    }
}

3、消息被拒

消息生产者代码

publicclassProducer {
privatestaticfinalStringNORMAL_EXCHANGE="normal_exchange";
publicstaticvoidmain(String[] argv) throwsException {
try (Channelchannel=RabbitMqUtils.getChannel()) {
channel.exchangeDeclare(NORMAL_EXCHANGE, BuiltinExchangeType.DIRECT);
//该信息是用作演示队列个数限制for (inti=1; i<11 ; i++) {
Stringmessage="info"+i;
channel.basicPublish(NORMAL_EXCHANGE,"zhangsan",null, message.getBytes());
System.out.println("生产者发送消息:"+message);
            }
        }
    }
}

C1 消费者代码(启动之后关闭该消费者模拟其接收不到消息)

publicclassConsumer01 {
//普通交换机名称privatestaticfinalStringNORMAL_EXCHANGE="normal_exchange";
//死信交换机名称privatestaticfinalStringDEAD_EXCHANGE="dead_exchange";
publicstaticvoidmain(String[] argv) throwsException {
Channelchannel=RabbitUtils.getChannel();
//声明死信和普通交换机 类型为 directchannel.exchangeDeclare(NORMAL_EXCHANGE, BuiltinExchangeType.DIRECT);
channel.exchangeDeclare(DEAD_EXCHANGE, BuiltinExchangeType.DIRECT);
//声明死信队列StringdeadQueue="dead-queue";
channel.queueDeclare(deadQueue, false, false, false, null);
//死信队列绑定死信交换机与 routingkeychannel.queueBind(deadQueue, DEAD_EXCHANGE, "lisi");
//正常队列绑定死信队列信息Map<String, Object>params=newHashMap<>();
//正常队列设置死信交换机 参数 key 是固定值params.put("x-dead-letter-exchange", DEAD_EXCHANGE);
//正常队列设置死信 routing-key 参数 key 是固定值params.put("x-dead-letter-routing-key", "lisi");
StringnormalQueue="normal-queue";
channel.queueDeclare(normalQueue, false, false, false, params);
channel.queueBind(normalQueue, NORMAL_EXCHANGE, "zhangsan");
System.out.println("等待接收消息.....");
DeliverCallbackdeliverCallback= (consumerTag, delivery) -> {
Stringmessage=newString(delivery.getBody(), "UTF-8");
if(message.equals("info5")){
System.out.println("Consumer01 接收到消息"+message+"并拒绝签收该消息");
//requeue 设置为 false 代表拒绝重新入队 该队列如果配置了死信交换机将发送到死信队列中channel.basicReject(delivery.getEnvelope().getDeliveryTag(), false);
            }else {
System.out.println("Consumer01 接收到消息"+message);
channel.basicAck(delivery.getEnvelope().getDeliveryTag(), false);
            }
        };
booleanautoAck=false;
channel.basicConsume(normalQueue, autoAck, deliverCallback, consumerTag-> {
        });
    }
}

C2 消费者代码

publicclassConsumer02 {
privatestaticfinalStringDEAD_EXCHANGE="dead_exchange";
publicstaticvoidmain(String[] argv) throwsException {
Channelchannel=RabbitUtils.getChannel();
channel.exchangeDeclare(DEAD_EXCHANGE, BuiltinExchangeType.DIRECT);
StringdeadQueue="dead-queue";
channel.queueDeclare(deadQueue, false, false, false, null);
channel.queueBind(deadQueue, DEAD_EXCHANGE, "lisi");
System.out.println("等待接收死信队列消息.....");
DeliverCallbackdeliverCallback= (consumerTag, delivery) -> {
Stringmessage=newString(delivery.getBody(), "UTF-8");
System.out.println("Consumer02 接收死信队列的消息"+message);
        };
channel.basicConsume(deadQueue, true, deliverCallback, consumerTag-> {
        });
    }
}

启动消费者 1 然后再启动消费者 2

总结

以上就是RabbitMQ之死信队列的相关知识点，希望对你有所帮助。

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RabbitMQ之死信队列

文章目录

一、死信的概念

二、死信的来源

三、实战

1、消息 TTL 过期

2、队列达到最大长度

3、消息被拒

总结

中间件

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