RabbitMQ之死信队列

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；

死信的来源

• 消息TTL过期
• 队列达到最大长度（队列已满，无法再往队列中添加数据）
• 消息被拒绝（basic.reject或basic.nack）且requeue=false

死信实战

代码架构图

消息TTL过期

参考代码架构图

public class Consumer01 {
    // 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";
    // 普通交换机名称
    private static final String NORMAL_QUEUE = "normal_queue";
    // 死信交换机名称
    private static final String DEAD_QUEUE = "dead_queue";

    public static void main(String[] args) throws Exception{
        Channel channel = RabbitMqUtils.getChannel();

        // 声明交换机类型
        channel.exchangeDeclare(NORMAL_EXCHANGE, BuiltinExchangeType.DIRECT);
        channel.exchangeDeclare(DEAD_EXCHANGE, BuiltinExchangeType.DIRECT);

        //声明普通队列
        Map<String, Object> arguments = new HashMap<>();
        // 过期时间
        arguments.put("x-message-ttl", 10000);
        // 正常队列设置死信队列
        arguments.put("x-dead-letter-exchange", DEAD_EXCHANGE);
        // 设置死信RoutingKey
        arguments.put("x-dead-letter-routing-key", "lisa");
        channel.queueDeclare(NORMAL_QUEUE, false, false, false, arguments);
        //声明死信队列
        channel.queueDeclare(DEAD_QUEUE, false, false, false, null);

        // 绑定普通的交换机与普通队列
        channel.queueBind(NORMAL_QUEUE, NORMAL_EXCHANGE, "zhangsan");
        // 绑定死信交换机与死信队列
        channel.queueBind(DEAD_QUEUE, DEAD_EXCHANGE, "lisa");

        // 接收消息并消费
        DeliverCallback deliverCallback = (consumerTag, message) -> {
            System.out.println("Consumer01接收的消息为: " + new String(message.getBody(), "UTF-8"));
        };
        channel.basicConsume(NORMAL_QUEUE, true, deliverCallback, consumerTag -> {});
    }

}

public class Producer {
    // 普通交换机
    private static final String NORMAL_EXCHANGE = "normal_exchange";

    public static void main(String[] args) throws Exception{
        Channel channel = RabbitMqUtils.getChannel();

        // 死信消息 设置TTL时间 单位ms
        AMQP.BasicProperties properties =
                new AMQP.BasicProperties()
                    .builder().expiration("10000").build();
        for (int i = 1; i < 11; i++) {
            String message = "info" + i;
            channel.basicPublish(NORMAL_EXCHANGE, "zhangsan", properties, message.getBytes());
        }
    }
}

public class Consumer02 {
    // 普通交换机名称
    private static final String NORMAL_QUEUE = "normal_queue";

    public static void main(String[] args) throws Exception{
        Channel channel = RabbitMqUtils.getChannel();

        // 接收消息并消费
        DeliverCallback deliverCallback = (consumerTag, message) -> {
            System.out.println("Consumer02接收的消息为: " + new String(message.getBody(), "UTF-8"));
        };
        channel.basicConsume(NORMAL_QUEUE, true, deliverCallback, consumerTag -> {});
    }

}

队列达到最大长度

超出队列的限制部分将进入死信队列；

public class Consumer01 {
    // 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";
    // 普通交换机名称
    private static final String NORMAL_QUEUE = "normal_queue";
    // 死信交换机名称
    private static final String DEAD_QUEUE = "dead_queue";

    public static void main(String[] args) throws Exception{
        Channel channel = RabbitMqUtils.getChannel();

        // 声明交换机类型
        channel.exchangeDeclare(NORMAL_EXCHANGE, BuiltinExchangeType.DIRECT);
        channel.exchangeDeclare(DEAD_EXCHANGE, BuiltinExchangeType.DIRECT);

        //声明普通队列
        Map<String, Object> arguments = new HashMap<>();
        // 过期时间
        arguments.put("x-message-ttl", 10000);
        // 正常队列设置死信队列
        arguments.put("x-dead-letter-exchange", DEAD_EXCHANGE);
        // 设置死信RoutingKey
        arguments.put("x-dead-letter-routing-key", "lisa");
        // 设置正常队列长度的限制
        arguments.put("x-max-length", 6);
        channel.queueDeclare(NORMAL_QUEUE, false, false, false, arguments);
        //声明死信队列
        channel.queueDeclare(DEAD_QUEUE, false, false, false, null);

        // 绑定普通的交换机与普通队列
        channel.queueBind(NORMAL_QUEUE, NORMAL_EXCHANGE, "zhangsan");
        // 绑定死信交换机与死信队列
        channel.queueBind(DEAD_QUEUE, DEAD_EXCHANGE, "lisa");

        // 接收消息并消费
        DeliverCallback deliverCallback = (consumerTag, message) -> {
            System.out.println("Consumer01接收的消息为: " + new String(message.getBody(), "UTF-8"));
        };
        channel.basicConsume(NORMAL_QUEUE, true, deliverCallback, consumerTag -> {});
    }

}

消息被拒

public class Consumer01 {
    // 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";
    // 普通交换机名称
    private static final String NORMAL_QUEUE = "normal_queue";
    // 死信交换机名称
    private static final String DEAD_QUEUE = "dead_queue";

    public static void main(String[] args) throws Exception{
        Channel channel = RabbitMqUtils.getChannel();

        // 声明交换机类型
        channel.exchangeDeclare(NORMAL_EXCHANGE, BuiltinExchangeType.DIRECT);
        channel.exchangeDeclare(DEAD_EXCHANGE, BuiltinExchangeType.DIRECT);

        //声明普通队列
        Map<String, Object> arguments = new HashMap<>();
        // 过期时间
        arguments.put("x-message-ttl", 10000);
        // 正常队列设置死信队列
        arguments.put("x-dead-letter-exchange", DEAD_EXCHANGE);
        // 设置死信RoutingKey
        arguments.put("x-dead-letter-routing-key", "lisa");
        // 设置正常队列长度的限制
//        arguments.put("x-max-length", 6);
        channel.queueDeclare(NORMAL_QUEUE, false, false, false, arguments);
        //声明死信队列
        channel.queueDeclare(DEAD_QUEUE, false, false, false, null);

        // 绑定普通的交换机与普通队列
        channel.queueBind(NORMAL_QUEUE, NORMAL_EXCHANGE, "zhangsan");
        // 绑定死信交换机与死信队列
        channel.queueBind(DEAD_QUEUE, DEAD_EXCHANGE, "lisa");

        // 接收消息并消费
        DeliverCallback deliverCallback = (consumerTag, message) -> {
            System.out.println("Consumer01接收的消息为: " + new String(message.getBody(), "UTF-8"));
            if (message.equals("info5")){
                System.out.println("此消息是被拒绝的");
                channel.basicReject(message.getEnvelope().getDeliveryTag(), false);
            }else {
                System.out.println("接收的消息" + message);
                channel.basicAck(message.getEnvelope().getDeliveryTag(), false);
            }
        };
        channel.basicConsume(NORMAL_QUEUE, true, deliverCallback, consumerTag -> {});
    }

}